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Remove old lguest I/O infrrasructure.

Browse Source 
This patch gets rid of the old lguest host I/O infrastructure and
replaces it with a single hypercall "LHCALL_NOTIFY" which takes an
address.

The main change is the removal of io.c: that mainly did inter-guest
I/O, which virtio doesn't yet support.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2007-10-22 11:24:10 +10:00
parent 0ca49ca946
commit 15045275c3
8 changed files with 21 additions and 752 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/lguest/Makefile
View File

@ -1,7 +1,7 @@
# Host requires the other files, which can be a module.
obj-$(CONFIG_LGUEST) += lg.o
lg-y = core.o hypercalls.o page_tables.o interrupts_and_traps.o \
segments.o io.o lguest_user.o
segments.o lguest_user.o
lg-$(CONFIG_X86_32) += x86/switcher_32.o x86/core.o

12
drivers/lguest/core.c
View File

@ -202,13 +202,12 @@ int run_guest(struct lguest *lg, unsigned long __user *user)
if (lg->hcall)
do_hypercalls(lg);
/* It's possible the Guest did a SEND_DMA hypercall to the
/* It's possible the Guest did a NOTIFY hypercall to the
* Launcher, in which case we return from the read() now. */
if (lg->dma_is_pending) {
if (put_user(lg->pending_dma, user) ||
put_user(lg->pending_key, user+1))
if (lg->pending_notify) {
if (put_user(lg->pending_notify, user))
return -EFAULT;
return sizeof(unsigned long)*2;
return sizeof(lg->pending_notify);
}
/* Check for signals */
@ -288,9 +287,6 @@ static int __init init(void)
if (err)
goto unmap;
/* The I/O subsystem needs some things initialized. */
lguest_io_init();
/* We might need to reserve an interrupt vector. */
err = init_interrupts();
if (err)

26
drivers/lguest/hypercalls.c
View File

@ -60,22 +60,9 @@ static void do_hcall(struct lguest *lg, struct hcall_args *args)
else
guest_pagetable_flush_user(lg);
break;
case LHCALL_BIND_DMA:
/* BIND_DMA really wants four arguments, but it's the only call
* which does. So the Guest packs the number of buffers and
* the interrupt number into the final argument, and we decode
* it here. This can legitimately fail, since we currently
* place a limit on the number of DMA pools a Guest can have.
* So we return true or false from this call. */
args->arg0 = bind_dma(lg, args->arg1, args->arg2,
args->arg3 >> 8, args->arg3 & 0xFF);
break;
/* All these calls simply pass the arguments through to the right
* routines. */
case LHCALL_SEND_DMA:
send_dma(lg, args->arg1, args->arg2);
break;
case LHCALL_NEW_PGTABLE:
guest_new_pagetable(lg, args->arg1);
break;
@ -99,6 +86,9 @@ static void do_hcall(struct lguest *lg, struct hcall_args *args)
/* Similarly, this sets the halted flag for run_guest(). */
lg->halted = 1;
break;
case LHCALL_NOTIFY:
lg->pending_notify = args->arg1;
break;
default:
if (lguest_arch_do_hcall(lg, args))
kill_guest(lg, "Bad hypercall %li\n", args->arg0);
@ -156,9 +146,9 @@ static void do_async_hcalls(struct lguest *lg)
break;
}
/* Stop doing hypercalls if we've just done a DMA to the
* Launcher: it needs to service this first. */
if (lg->dma_is_pending)
/* Stop doing hypercalls if they want to notify the Launcher:
* it needs to service this first. */
if (lg->pending_notify)
break;
}
}
@ -220,9 +210,9 @@ void do_hypercalls(struct lguest *lg)
do_async_hcalls(lg);
/* If we stopped reading the hypercall ring because the Guest did a
* SEND_DMA to the Launcher, we want to return now. Otherwise we do
* NOTIFY to the Launcher, we want to return now. Otherwise we do
* the hypercall. */
if (!lg->dma_is_pending) {
if (!lg->pending_notify) {
do_hcall(lg, lg->hcall);
/* Tricky point: we reset the hcall pointer to mark the
* hypercall as "done". We use the hcall pointer rather than

628
drivers/lguest/io.c
View File

@ -1,628 +0,0 @@
/*P:300 The I/O mechanism in lguest is simple yet flexible, allowing the Guest
* to talk to the Launcher or directly to another Guest. It uses familiar
* concepts of DMA and interrupts, plus some neat code stolen from
* futexes... :*/
/* Copyright (C) 2006 Rusty Russell IBM Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/types.h>
#include <linux/futex.h>
#include <linux/jhash.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/uaccess.h>
#include "lg.h"
/*L:300
* I/O
*
* Getting data in and out of the Guest is quite an art. There are numerous
* ways to do it, and they all suck differently. We try to keep things fairly
* close to "real" hardware so our Guest's drivers don't look like an alien
* visitation in the middle of the Linux code, and yet make sure that Guests
* can talk directly to other Guests, not just the Launcher.
*
* To do this, the Guest gives us a key when it binds or sends DMA buffers.
* The key corresponds to a "physical" address inside the Guest (ie. a virtual
* address inside the Launcher process). We don't, however, use this key
* directly.
*
* We want Guests which share memory to be able to DMA to each other: two
* Launchers can mmap memory the same file, then the Guests can communicate.
* Fortunately, the futex code provides us with a way to get a "union
* futex_key" corresponding to the memory lying at a virtual address: if the
* two processes share memory, the "union futex_key" for that memory will match
* even if the memory is mapped at different addresses in each. So we always
* convert the keys to "union futex_key"s to compare them.
*
* Before we dive into this though, we need to look at another set of helper
* routines used throughout the Host kernel code to access Guest memory.
:*/
static struct list_head dma_hash[61];
/* An unfortunate side effect of the Linux double-linked list implementation is
* that there's no good way to statically initialize an array of linked
* lists. */
void lguest_io_init(void)
{
unsigned int i;
for (i = 0; i < ARRAY_SIZE(dma_hash); i++)
INIT_LIST_HEAD(&dma_hash[i]);
}
/* FIXME: allow multi-page lengths. */
static int check_dma_list(struct lguest *lg, const struct lguest_dma *dma)
{
unsigned int i;
for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
if (!dma->len[i])
return 1;
if (!lguest_address_ok(lg, dma->addr[i], dma->len[i]))
goto kill;
if (dma->len[i] > PAGE_SIZE)
goto kill;
/* We could do over a page, but is it worth it? */
if ((dma->addr[i] % PAGE_SIZE) + dma->len[i] > PAGE_SIZE)
goto kill;
}
return 1;
kill:
kill_guest(lg, "bad DMA entry: %u@%#lx", dma->len[i], dma->addr[i]);
return 0;
}
/*L:330 This is our hash function, using the wonderful Jenkins hash.
*
* The futex key is a union with three parts: an unsigned long word, a pointer,
* and an int "offset". We could use jhash_2words() which takes three u32s.
* (Ok, the hash functions are great: the naming sucks though).
*
* It's nice to be portable to 64-bit platforms, so we use the more generic
* jhash2(), which takes an array of u32, the number of u32s, and an initial
* u32 to roll in. This is uglier, but breaks down to almost the same code on
* 32-bit platforms like this one.
*
* We want a position in the array, so we modulo ARRAY_SIZE(dma_hash) (ie. 61).
*/
static unsigned int hash(const union futex_key *key)
{
return jhash2((u32*)&key->both.word,
(sizeof(key->both.word)+sizeof(key->both.ptr))/4,
key->both.offset)
% ARRAY_SIZE(dma_hash);
}
/* This is a convenience routine to compare two keys. It's a much bemoaned C
* weakness that it doesn't allow '==' on structures or unions, so we have to
* open-code it like this. */
static inline int key_eq(const union futex_key *a, const union futex_key *b)
{
return (a->both.word == b->both.word
&& a->both.ptr == b->both.ptr
&& a->both.offset == b->both.offset);
}
/*L:360 OK, when we need to actually free up a Guest's DMA array we do several
* things, so we have a convenient function to do it.
*
* The caller must hold a read lock on dmainfo owner's current->mm->mmap_sem
* for the drop_futex_key_refs(). */
static void unlink_dma(struct lguest_dma_info *dmainfo)
{
/* You locked this too, right? */
BUG_ON(!mutex_is_locked(&lguest_lock));
/* This is how we know that the entry is free. */
dmainfo->interrupt = 0;
/* Remove it from the hash table. */
list_del(&dmainfo->list);
/* Drop the references we were holding (to the inode or mm). */
drop_futex_key_refs(&dmainfo->key);
}
/*L:350 This is the routine which we call when the Guest asks to unregister a
* DMA array attached to a given key. Returns true if the array was found. */
static int unbind_dma(struct lguest *lg,
const union futex_key *key,
unsigned long dmas)
{
int i, ret = 0;
/* We don't bother with the hash table, just look through all this
* Guest's DMA arrays. */
for (i = 0; i < LGUEST_MAX_DMA; i++) {
/* In theory it could have more than one array on the same key,
* or one array on multiple keys, so we check both */
if (key_eq(key, &lg->dma[i].key) && dmas == lg->dma[i].dmas) {
unlink_dma(&lg->dma[i]);
ret = 1;
break;
}
}
return ret;
}
/*L:340 BIND_DMA: this is the hypercall which sets up an array of "struct
* lguest_dma" for receiving I/O.
*
* The Guest wants to bind an array of "struct lguest_dma"s to a particular key
* to receive input. This only happens when the Guest is setting up a new
* device, so it doesn't have to be very fast.
*
* It returns 1 on a successful registration (it can fail if we hit the limit
* of registrations for this Guest).
*/
int bind_dma(struct lguest *lg,
unsigned long ukey, unsigned long dmas, u16 numdmas, u8 interrupt)
{
unsigned int i;
int ret = 0;
union futex_key key;
/* Futex code needs the mmap_sem. */
struct rw_semaphore *fshared = &current->mm->mmap_sem;
/* Invalid interrupt? (We could kill the guest here). */
if (interrupt >= LGUEST_IRQS)
return 0;
/* We need to grab the Big Lguest Lock, because other Guests may be
* trying to look through this Guest's DMAs to send something while
* we're doing this. */
mutex_lock(&lguest_lock);
down_read(fshared);
if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) {
kill_guest(lg, "bad dma key %#lx", ukey);
goto unlock;
}
/* We want to keep this key valid once we drop mmap_sem, so we have to
* hold a reference. */
get_futex_key_refs(&key);
/* If the Guest specified an interrupt of 0, that means they want to
* unregister this array of "struct lguest_dma"s. */
if (interrupt == 0)
ret = unbind_dma(lg, &key, dmas);
else {
/* Look through this Guest's dma array for an unused entry. */
for (i = 0; i < LGUEST_MAX_DMA; i++) {
/* If the interrupt is non-zero, the entry is already
* used. */
if (lg->dma[i].interrupt)
continue;
/* OK, a free one! Fill on our details. */
lg->dma[i].dmas = dmas;
lg->dma[i].num_dmas = numdmas;
lg->dma[i].next_dma = 0;
lg->dma[i].key = key;
lg->dma[i].owner = lg;
lg->dma[i].interrupt = interrupt;
/* Now we add it to the hash table: the position
* depends on the futex key that we got. */
list_add(&lg->dma[i].list, &dma_hash[hash(&key)]);
/* Success! */
ret = 1;
goto unlock;
}
}
/* If we didn't find a slot to put the key in, drop the reference
* again. */
drop_futex_key_refs(&key);
unlock:
/* Unlock and out. */
up_read(fshared);
mutex_unlock(&lguest_lock);
return ret;
}
/*L:385 Note that our routines to access a different Guest's memory are called
* lgread_other() and lgwrite_other(): these names emphasize that they are only
* used when the Guest is *not* the current Guest.
*
* The interface for copying from another process's memory is called
* access_process_vm(), with a final argument of 0 for a read, and 1 for a
* write.
*
* We need lgread_other() to read the destination Guest's "struct lguest_dma"
* array. */
static int lgread_other(struct lguest *lg,
void *buf, u32 addr, unsigned bytes)
{
if (!lguest_address_ok(lg, addr, bytes)
|| access_process_vm(lg->tsk, (unsigned long)lg->mem_base + addr,
buf, bytes, 0) != bytes) {
memset(buf, 0, bytes);
kill_guest(lg, "bad address in registered DMA struct");
return 0;
}
return 1;
}
/* "lgwrite()" to another Guest: used to update the destination "used_len" once
* we've transferred data into the buffer. */
static int lgwrite_other(struct lguest *lg, u32 addr,
const void *buf, unsigned bytes)
{
if (!lguest_address_ok(lg, addr, bytes)
|| access_process_vm(lg->tsk, (unsigned long)lg->mem_base + addr,
(void *)buf, bytes, 1) != bytes) {
kill_guest(lg, "bad address writing to registered DMA");
return 0;
}
return 1;
}
/*L:400 This is the generic engine which copies from a source "struct
* lguest_dma" from this Guest into another Guest's "struct lguest_dma". The
* destination Guest's pages have already been mapped, as contained in the
* pages array.
*
* If you're wondering if there's a nice "copy from one process to another"
* routine, so was I. But Linux isn't really set up to copy between two
* unrelated processes, so we have to write it ourselves.
*/
static u32 copy_data(struct lguest *srclg,
const struct lguest_dma *src,
const struct lguest_dma *dst,
struct page *pages[])
{
unsigned int totlen, si, di, srcoff, dstoff;
void *maddr = NULL;
/* We return the total length transferred. */
totlen = 0;
/* We keep indexes into the source and destination "struct lguest_dma",
* and an offset within each region. */
si = di = 0;
srcoff = dstoff = 0;
/* We loop until the source or destination is exhausted. */
while (si < LGUEST_MAX_DMA_SECTIONS && src->len[si]
&& di < LGUEST_MAX_DMA_SECTIONS && dst->len[di]) {
/* We can only transfer the rest of the src buffer, or as much
* as will fit into the destination buffer. */
u32 len = min(src->len[si] - srcoff, dst->len[di] - dstoff);
/* For systems using "highmem" we need to use kmap() to access
* the page we want. We often use the same page over and over,
* so rather than kmap() it on every loop, we set the maddr
* pointer to NULL when we need to move to the next
* destination page. */
if (!maddr)
maddr = kmap(pages[di]);
/* Copy directly from (this Guest's) source address to the
* destination Guest's kmap()ed buffer. Note that maddr points
* to the start of the page: we need to add the offset of the
* destination address and offset within the buffer. */
/* FIXME: This is not completely portable. I looked at
* copy_to_user_page(), and some arch's seem to need special
* flushes. x86 is fine. */
if (copy_from_user(maddr + (dst->addr[di] + dstoff)%PAGE_SIZE,
srclg->mem_base+src->addr[si], len) != 0) {
/* If a copy failed, it's the source's fault. */
kill_guest(srclg, "bad address in sending DMA");
totlen = 0;
break;
}
/* Increment the total and src & dst offsets */
totlen += len;
srcoff += len;
dstoff += len;
/* Presumably we reached the end of the src or dest buffers: */
if (srcoff == src->len[si]) {
/* Move to the next buffer at offset 0 */
si++;
srcoff = 0;
}
if (dstoff == dst->len[di]) {
/* We need to unmap that destination page and reset
* maddr ready for the next one. */
kunmap(pages[di]);
maddr = NULL;
di++;
dstoff = 0;
}
}
/* If we still had a page mapped at the end, unmap now. */
if (maddr)
kunmap(pages[di]);
return totlen;
}
/*L:390 This is how we transfer a "struct lguest_dma" from the source Guest
* (the current Guest which called SEND_DMA) to another Guest. */
static u32 do_dma(struct lguest *srclg, const struct lguest_dma *src,
struct lguest *dstlg, const struct lguest_dma *dst)
{
int i;
u32 ret;
struct page *pages[LGUEST_MAX_DMA_SECTIONS];
/* We check that both source and destination "struct lguest_dma"s are
* within the bounds of the source and destination Guests */
if (!check_dma_list(dstlg, dst) || !check_dma_list(srclg, src))
return 0;
/* We need to map the pages which correspond to each parts of
* destination buffer. */
for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) {
if (dst->len[i] == 0)
break;
/* get_user_pages() is a complicated function, especially since
* we only want a single page. But it works, and returns the
* number of pages. Note that we're holding the destination's
* mmap_sem, as get_user_pages() requires. */
if (get_user_pages(dstlg->tsk, dstlg->mm,
(unsigned long)dstlg->mem_base+dst->addr[i],
1, 1, 1, pages+i, NULL)
!= 1) {
/* This means the destination gave us a bogus buffer */
kill_guest(dstlg, "Error mapping DMA pages");
ret = 0;
goto drop_pages;
}
}
/* Now copy the data until we run out of src or dst. */
ret = copy_data(srclg, src, dst, pages);
drop_pages:
while (--i >= 0)
put_page(pages[i]);
return ret;
}
/*L:380 Transferring data from one Guest to another is not as simple as I'd
* like. We've found the "struct lguest_dma_info" bound to the same address as
* the send, we need to copy into it.
*
* This function returns true if the destination array was empty. */
static int dma_transfer(struct lguest *srclg,
unsigned long udma,
struct lguest_dma_info *dst)
{
struct lguest_dma dst_dma, src_dma;
struct lguest *dstlg;
u32 i, dma = 0;
/* From the "struct lguest_dma_info" we found in the hash, grab the
* Guest. */
dstlg = dst->owner;
/* Read in the source "struct lguest_dma" handed to SEND_DMA. */
lgread(srclg, &src_dma, udma, sizeof(src_dma));
/* We need the destination's mmap_sem, and we already hold the source's
* mmap_sem for the futex key lookup. Normally this would suggest that
* we could deadlock if the destination Guest was trying to send to
* this source Guest at the same time, which is another reason that all
* I/O is done under the big lguest_lock. */
down_read(&dstlg->mm->mmap_sem);
/* Look through the destination DMA array for an available buffer. */
for (i = 0; i < dst->num_dmas; i++) {
/* We keep a "next_dma" pointer which often helps us avoid
* looking at lots of previously-filled entries. */
dma = (dst->next_dma + i) % dst->num_dmas;
if (!lgread_other(dstlg, &dst_dma,
dst->dmas + dma * sizeof(struct lguest_dma),
sizeof(dst_dma))) {
goto fail;
}
if (!dst_dma.used_len)
break;
}
/* If we found a buffer, we do the actual data copy. */
if (i != dst->num_dmas) {
unsigned long used_lenp;
unsigned int ret;
ret = do_dma(srclg, &src_dma, dstlg, &dst_dma);
/* Put used length in the source "struct lguest_dma"'s used_len
* field. It's a little tricky to figure out where that is,
* though. */
lgwrite_u32(srclg,
udma+offsetof(struct lguest_dma, used_len), ret);
/* Tranferring 0 bytes is OK if the source buffer was empty. */
if (ret == 0 && src_dma.len[0] != 0)
goto fail;
/* The destination Guest might be running on a different CPU:
* we have to make sure that it will see the "used_len" field
* change to non-zero *after* it sees the data we copied into
* the buffer. Hence a write memory barrier. */
wmb();
/* Figuring out where the destination's used_len field for this
* "struct lguest_dma" in the array is also a little ugly. */
used_lenp = dst->dmas
+ dma * sizeof(struct lguest_dma)
+ offsetof(struct lguest_dma, used_len);
lgwrite_other(dstlg, used_lenp, &ret, sizeof(ret));
/* Move the cursor for next time. */
dst->next_dma++;
}
up_read(&dstlg->mm->mmap_sem);
/* We trigger the destination interrupt, even if the destination was
* empty and we didn't transfer anything: this gives them a chance to
* wake up and refill. */
set_bit(dst->interrupt, dstlg->irqs_pending);
/* Wake up the destination process. */
wake_up_process(dstlg->tsk);
/* If we passed the last "struct lguest_dma", the receive had no
* buffers left. */
return i == dst->num_dmas;
fail:
up_read(&dstlg->mm->mmap_sem);
return 0;
}
/*L:370 This is the counter-side to the BIND_DMA hypercall; the SEND_DMA
* hypercall. We find out who's listening, and send to them. */
void send_dma(struct lguest *lg, unsigned long ukey, unsigned long udma)
{
union futex_key key;
int empty = 0;
struct rw_semaphore *fshared = &current->mm->mmap_sem;
again:
mutex_lock(&lguest_lock);
down_read(fshared);
/* Get the futex key for the key the Guest gave us */
if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) {
kill_guest(lg, "bad sending DMA key");
goto unlock;
}
/* Since the key must be a multiple of 4, the futex key uses the lower
* bit of the "offset" field (which would always be 0) to indicate a
* mapping which is shared with other processes (ie. Guests). */
if (key.shared.offset & 1) {
struct lguest_dma_info *i;
/* Look through the hash for other Guests. */
list_for_each_entry(i, &dma_hash[hash(&key)], list) {
/* Don't send to ourselves (would deadlock). */
if (i->owner->mm == lg->mm)
continue;
if (!key_eq(&key, &i->key))
continue;
/* If dma_transfer() tells us the destination has no
* available buffers, we increment "empty". */
empty += dma_transfer(lg, udma, i);
break;
}
/* If the destination is empty, we release our locks and
* give the destination Guest a brief chance to restock. */
if (empty == 1) {
/* Give any recipients one chance to restock. */
up_read(&current->mm->mmap_sem);
mutex_unlock(&lguest_lock);
/* Next time, we won't try again. */
empty++;
goto again;
}
} else {
/* Private mapping: Guest is sending to its Launcher. We set
* the "dma_is_pending" flag so that the main loop will exit
* and the Launcher's read() from /dev/lguest will return. */
lg->dma_is_pending = 1;
lg->pending_dma = udma;
lg->pending_key = ukey;
}
unlock:
up_read(fshared);
mutex_unlock(&lguest_lock);
}
/*:*/
void release_all_dma(struct lguest *lg)
{
unsigned int i;
BUG_ON(!mutex_is_locked(&lguest_lock));
down_read(&lg->mm->mmap_sem);
for (i = 0; i < LGUEST_MAX_DMA; i++) {
if (lg->dma[i].interrupt)
unlink_dma(&lg->dma[i]);
}
up_read(&lg->mm->mmap_sem);
}
/*M:007 We only return a single DMA buffer to the Launcher, but it would be
* more efficient to return a pointer to the entire array of DMA buffers, which
* it can cache and choose one whenever it wants.
*
* Currently the Launcher uses a write to /dev/lguest, and the return value is
* the address of the DMA structure with the interrupt number placed in
* dma->used_len. If we wanted to return the entire array, we need to return
* the address, array size and interrupt number: this seems to require an
* ioctl(). :*/
/*L:320 This routine looks for a DMA buffer registered by the Guest on the
* given key (using the BIND_DMA hypercall). */
unsigned long get_dma_buffer(struct lguest *lg,
unsigned long ukey, unsigned long *interrupt)
{
unsigned long ret = 0;
union futex_key key;
struct lguest_dma_info *i;
struct rw_semaphore *fshared = &current->mm->mmap_sem;
/* Take the Big Lguest Lock to stop other Guests sending this Guest DMA
* at the same time. */
mutex_lock(&lguest_lock);
/* To match between Guests sharing the same underlying memory we steal
* code from the futex infrastructure. This requires that we hold the
* "mmap_sem" for our process (the Launcher), and pass it to the futex
* code. */
down_read(fshared);
/* This can fail if it's not a valid address, or if the address is not
* divisible by 4 (the futex code needs that, we don't really). */
if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) {
kill_guest(lg, "bad registered DMA buffer");
goto unlock;
}
/* Search the hash table for matching entries (the Launcher can only
* send to its own Guest for the moment, so the entry must be for this
* Guest) */
list_for_each_entry(i, &dma_hash[hash(&key)], list) {
if (key_eq(&key, &i->key) && i->owner == lg) {
unsigned int j;
/* Look through the registered DMA array for an
* available buffer. */
for (j = 0; j < i->num_dmas; j++) {
struct lguest_dma dma;
ret = i->dmas + j * sizeof(struct lguest_dma);
lgread(lg, &dma, ret, sizeof(dma));
if (dma.used_len == 0)
break;
}
/* Store the interrupt the Guest wants when the buffer
* is used. */
*interrupt = i->interrupt;
break;
}
}
unlock:
up_read(fshared);
mutex_unlock(&lguest_lock);
return ret;
}
/*:*/
/*L:410 This really has completed the Launcher. Not only have we now finished
* the longest chapter in our journey, but this also means we are over halfway
* through!
*
* Enough prevaricating around the bush: it is time for us to dive into the
* core of the Host, in "make Host".
*/

27
drivers/lguest/lg.h
View File

@ -5,7 +5,6 @@
#include <linux/types.h>
#include <linux/init.h>
#include <linux/stringify.h>
#include <linux/futex.h>
#include <linux/lguest.h>
#include <linux/lguest_launcher.h>
#include <linux/wait.h>
@ -17,17 +16,6 @@
void free_pagetables(void);
int init_pagetables(struct page **switcher_page, unsigned int pages);
struct lguest_dma_info
{
struct list_head list;
union futex_key key;
unsigned long dmas;
struct lguest *owner;
u16 next_dma;
u16 num_dmas;
u8 interrupt; /* 0 when not registered */
};
struct pgdir
{
unsigned long gpgdir;
@ -90,15 +78,11 @@ struct lguest
struct task_struct *wake;
unsigned long noirq_start, noirq_end;
int dma_is_pending;
unsigned long pending_dma; /* struct lguest_dma */
unsigned long pending_key; /* address they're sending to */
unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */
unsigned int stack_pages;
u32 tsc_khz;
struct lguest_dma_info dma[LGUEST_MAX_DMA];
/* Dead? */
const char *dead;
@ -184,15 +168,6 @@ extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];
int lguest_device_init(void);
void lguest_device_remove(void);
/* io.c: */
void lguest_io_init(void);
int bind_dma(struct lguest *lg,
unsigned long key, unsigned long udma, u16 numdmas, u8 interrupt);
void send_dma(struct lguest *info, unsigned long key, unsigned long udma);
void release_all_dma(struct lguest *lg);
unsigned long get_dma_buffer(struct lguest *lg, unsigned long key,
unsigned long *interrupt);
/* hypercalls.c: */
void do_hypercalls(struct lguest *lg);
void write_timestamp(struct lguest *lg);

39
drivers/lguest/lguest_user.c
View File

@ -2,37 +2,12 @@
* controls and communicates with the Guest. For example, the first write will
* tell us the Guest's memory layout, pagetable, entry point and kernel address
* offset. A read will run the Guest until something happens, such as a signal
* or the Guest doing a DMA out to the Launcher. Writes are also used to get a
* DMA buffer registered by the Guest and to send the Guest an interrupt. :*/
* or the Guest doing a NOTIFY out to the Launcher. :*/
#include <linux/uaccess.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include "lg.h"
/*L:310 To send DMA into the Guest, the Launcher needs to be able to ask for a
* DMA buffer. This is done by writing LHREQ_GETDMA and the key to
* /dev/lguest. */
static long user_get_dma(struct lguest *lg, const unsigned long __user *input)
{
unsigned long key, udma, irq;
/* Fetch the key they wrote to us. */
if (get_user(key, input) != 0)
return -EFAULT;
/* Look for a free Guest DMA buffer bound to that key. */
udma = get_dma_buffer(lg, key, &irq);
if (!udma)
return -ENOENT;
/* We need to tell the Launcher what interrupt the Guest expects after
* the buffer is filled. We stash it in udma->used_len. */
lgwrite_u32(lg, udma + offsetof(struct lguest_dma, used_len), irq);
/* The (guest-physical) address of the DMA buffer is returned from
* the write(). */
return udma;
}
/*L:315 To force the Guest to stop running and return to the Launcher, the
* Waker sets writes LHREQ_BREAK and the value "1" to /dev/lguest. The
* Launcher then writes LHREQ_BREAK and "0" to release the Waker. */
@ -102,10 +77,10 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
return len;
}
/* If we returned from read() last time because the Guest sent DMA,
/* If we returned from read() last time because the Guest notified,
* clear the flag. */
if (lg->dma_is_pending)
lg->dma_is_pending = 0;
if (lg->pending_notify)
lg->pending_notify = 0;
/* Run the Guest until something interesting happens. */
return run_guest(lg, (unsigned long __user *)user);
@ -216,7 +191,7 @@ unlock:
/*L:010 The first operation the Launcher does must be a write. All writes
* start with a 32 bit number: for the first write this must be
* LHREQ_INITIALIZE to set up the Guest. After that the Launcher can use
* writes of other values to get DMA buffers and send interrupts. */
* writes of other values to send interrupts. */
static ssize_t write(struct file *file, const char __user *in,
size_t size, loff_t *off)
{
@ -245,8 +220,6 @@ static ssize_t write(struct file *file, const char __user *in,
switch (req) {
case LHREQ_INITIALIZE:
return initialize(file, input);
case LHREQ_GETDMA:
return user_get_dma(lg, input);
case LHREQ_IRQ:
return user_send_irq(lg, input);
case LHREQ_BREAK:
@ -276,8 +249,6 @@ static int close(struct inode *inode, struct file *file)
mutex_lock(&lguest_lock);
/* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
hrtimer_cancel(&lg->hrt);
/* Free any DMA buffers the Guest had bound. */
release_all_dma(lg);
/* Free up the shadow page tables for the Guest. */
free_guest_pagetable(lg);
/* Now all the memory cleanups are done, it's safe to release the

3
include/asm-x86/lguest_hcall.h
View File

@ -13,11 +13,10 @@
#define LHCALL_TS 8
#define LHCALL_SET_CLOCKEVENT 9
#define LHCALL_HALT 10
#define LHCALL_BIND_DMA 12
#define LHCALL_SEND_DMA 13
#define LHCALL_SET_PTE 14
#define LHCALL_SET_PMD 15
#define LHCALL_LOAD_TLS 16
#define LHCALL_NOTIFY 17
/*G:031 First, how does our Guest contact the Host to ask for privileged
* operations? There are two ways: the direct way is to make a "hypercall",

36
include/linux/lguest_launcher.h
View File

@ -10,40 +10,6 @@
/* How many devices? Assume each one wants up to two dma arrays per device. */
#define LGUEST_MAX_DEVICES (LGUEST_MAX_DMA/2)
/*D:200
* Lguest I/O
*
* The lguest I/O mechanism is the only way Guests can talk to devices. There
* are two hypercalls involved: SEND_DMA for output and BIND_DMA for input. In
* each case, "struct lguest_dma" describes the buffer: this contains 16
* addr/len pairs, and if there are fewer buffer elements the len array is
* terminated with a 0.
*
* I/O is organized by keys: BIND_DMA attaches buffers to a particular key, and
* SEND_DMA transfers to buffers bound to particular key. By convention, keys
* correspond to a physical address within the device's page. This means that
* devices will never accidentally end up with the same keys, and allows the
* Host use The Futex Trick (as we'll see later in our journey).
*
* SEND_DMA simply indicates a key to send to, and the physical address of the
* "struct lguest_dma" to send. The Host will write the number of bytes
* transferred into the "struct lguest_dma"'s used_len member.
*
* BIND_DMA indicates a key to bind to, a pointer to an array of "struct
* lguest_dma"s ready for receiving, the size of that array, and an interrupt
* to trigger when data is received. The Host will only allow transfers into
* buffers with a used_len of zero: it then sets used_len to the number of
* bytes transferred and triggers the interrupt for the Guest to process the
* new input. */
struct lguest_dma
{
/* 0 if free to be used, filled by the Host. */
__u32 used_len;
__u16 len[LGUEST_MAX_DMA_SECTIONS];
unsigned long addr[LGUEST_MAX_DMA_SECTIONS];
};
/*:*/
/* Where the Host expects the Guest to SEND_DMA console output to. */
#define LGUEST_CONSOLE_DMA_KEY 0
@ -95,7 +61,7 @@ struct lguest_device_desc {
enum lguest_req
{
LHREQ_INITIALIZE, /* + pfnlimit, pgdir, start, pageoffset */
LHREQ_GETDMA, /* + addr (returns &lguest_dma, irq in ->used_len) */
LHREQ_GETDMA, /* No longer used */
LHREQ_IRQ, /* + irq */
LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */
};