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KVM: s390: pv: add mmu_notifier

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Add an mmu_notifier for protected VMs. The callback function is
triggered when the mm is torn down, and will attempt to convert all
protected vCPUs to non-protected. This allows the mm teardown to use
the destroy page UVC instead of export.

Also make KVM select CONFIG_MMU_NOTIFIER, needed to use mmu_notifiers.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
Link: https://lore.kernel.org/r/20220628135619.32410-10-imbrenda@linux.ibm.com
Message-Id: <20220628135619.32410-10-imbrenda@linux.ibm.com>
[frankja@linux.ibm.com: Conflict resolution for mmu_notifier.h include
and struct kvm_s390_pv]
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2022-06-28 15:56:10 +02:00 committed by Janosch Frank
parent be48d86f77
commit ca2fd0609b
4 changed files with 39 additions and 0 deletions
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2
arch/s390/include/asm/kvm_host.h
View File

@ -20,6 +20,7 @@
#include <linux/seqlock.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/mmu_notifier.h>
#include <asm/debug.h>
#include <asm/cpu.h>
#include <asm/fpu/api.h>
@ -929,6 +930,7 @@ struct kvm_s390_pv {
unsigned long stor_base;
void *stor_var;
bool dumping;
struct mmu_notifier mmu_notifier;
};
struct kvm_arch{

1
arch/s390/kvm/Kconfig
View File

@ -34,6 +34,7 @@ config KVM
select SRCU
select KVM_VFIO
select INTERVAL_TREE
select MMU_NOTIFIER
help
Support hosting paravirtualized guest machines using the SIE
virtualization capability on the mainframe. This should work

10
arch/s390/kvm/kvm-s390.c
View File

@ -31,6 +31,7 @@
#include <linux/sched/signal.h>
#include <linux/string.h>
#include <linux/pgtable.h>
#include <linux/mmu_notifier.h>
#include <asm/asm-offsets.h>
#include <asm/lowcore.h>
@ -3198,6 +3199,15 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
*/
if (kvm_s390_pv_get_handle(kvm))
kvm_s390_pv_deinit_vm(kvm, &rc, &rrc);
/*
* Remove the mmu notifier only when the whole KVM VM is torn down,
* and only if one was registered to begin with. If the VM is
* currently not protected, but has been previously been protected,
* then it's possible that the notifier is still registered.
*/
if (kvm->arch.pv.mmu_notifier.ops)
mmu_notifier_unregister(&kvm->arch.pv.mmu_notifier, kvm->mm);
debug_unregister(kvm->arch.dbf);
free_page((unsigned long)kvm->arch.sie_page2);
if (!kvm_is_ucontrol(kvm))

26
arch/s390/kvm/pv.c
View File

@ -15,6 +15,7 @@
#include <asm/mman.h>
#include <linux/pagewalk.h>
#include <linux/sched/mm.h>
#include <linux/mmu_notifier.h>
#include "kvm-s390.h"
static void kvm_s390_clear_pv_state(struct kvm *kvm)
@ -188,6 +189,26 @@ int kvm_s390_pv_deinit_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
return -EIO;
}
static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
struct mm_struct *mm)
{
struct kvm *kvm = container_of(subscription, struct kvm, arch.pv.mmu_notifier);
u16 dummy;
/*
* No locking is needed since this is the last thread of the last user of this
* struct mm.
* When the struct kvm gets deinitialized, this notifier is also
* unregistered. This means that if this notifier runs, then the
* struct kvm is still valid.
*/
kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
}
static const struct mmu_notifier_ops kvm_s390_pv_mmu_notifier_ops = {
.release = kvm_s390_pv_mmu_notifier_release,
};
int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
{
struct uv_cb_cgc uvcb = {
@ -229,6 +250,11 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
return -EIO;
}
kvm->arch.gmap->guest_handle = uvcb.guest_handle;
/* Add the notifier only once. No races because we hold kvm->lock */
if (kvm->arch.pv.mmu_notifier.ops != &kvm_s390_pv_mmu_notifier_ops) {
kvm->arch.pv.mmu_notifier.ops = &kvm_s390_pv_mmu_notifier_ops;
mmu_notifier_register(&kvm->arch.pv.mmu_notifier, kvm->mm);
}
return 0;
}