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Merge branch 'pci/p2pdma'

Browse Source 
- Rename Rename upstream_bridge_distance() to calc_map_type_and_dist()
  (Logan Gunthorpe)

- Collect ACS list message in stack buffer to avoid sleeping (Logan
  Gunthorpe)

- Use correct calc_map_type_and_dist() return type (Logan Gunthorpe)

- Warn if host bridge not in whitelist (Logan Gunthorpe)

- Refactor pci_p2pdma_map_type() (Logan Gunthorpe)

- Avoid pci_get_slot(), which may sleep (Logan Gunthorpe)

- Simplify distance calculation in __calc_map_type_and_dist() and
  calc_map_type_and_dist_warn() (Christoph Hellwig)

- Finish RCU conversion of pdev->p2pdma (Eric Dumazet)

* pci/p2pdma:
  PCI/P2PDMA: Finish RCU conversion of pdev->p2pdma
  PCI/P2PDMA: Simplify distance calculation
  PCI/P2PDMA: Avoid pci_get_slot(), which may sleep
  PCI/P2PDMA: Refactor pci_p2pdma_map_type()
  PCI/P2PDMA: Warn if host bridge not in whitelist
  PCI/P2PDMA: Use correct calc_map_type_and_dist() return type
  PCI/P2PDMA: Collect acs list in stack buffer to avoid sleeping
  PCI/P2PDMA: Rename upstream_bridge_distance() and rework doc
This commit is contained in:
Bjorn Helgaas 2021-07-06 10:56:24 -05:00
commit c9fb9042c9
2 changed files with 205 additions and 173 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

376
drivers/pci/p2pdma.c
View File

@ -48,10 +48,14 @@ static ssize_t size_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct pci_dev *pdev = to_pci_dev(dev);
struct pci_p2pdma *p2pdma;
size_t size = 0;
if (pdev->p2pdma->pool)
size = gen_pool_size(pdev->p2pdma->pool);
rcu_read_lock();
p2pdma = rcu_dereference(pdev->p2pdma);
if (p2pdma && p2pdma->pool)
size = gen_pool_size(p2pdma->pool);
rcu_read_unlock();
return scnprintf(buf, PAGE_SIZE, "%zd\n", size);
}
@ -61,10 +65,14 @@ static ssize_t available_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct pci_dev *pdev = to_pci_dev(dev);
struct pci_p2pdma *p2pdma;
size_t avail = 0;
if (pdev->p2pdma->pool)
avail = gen_pool_avail(pdev->p2pdma->pool);
rcu_read_lock();
p2pdma = rcu_dereference(pdev->p2pdma);
if (p2pdma && p2pdma->pool)
avail = gen_pool_avail(p2pdma->pool);
rcu_read_unlock();
return scnprintf(buf, PAGE_SIZE, "%zd\n", avail);
}
@ -74,9 +82,16 @@ static ssize_t published_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct pci_dev *pdev = to_pci_dev(dev);
struct pci_p2pdma *p2pdma;
bool published = false;
return scnprintf(buf, PAGE_SIZE, "%d\n",
pdev->p2pdma->p2pmem_published);
rcu_read_lock();
p2pdma = rcu_dereference(pdev->p2pdma);
if (p2pdma)
published = p2pdma->p2pmem_published;
rcu_read_unlock();
return scnprintf(buf, PAGE_SIZE, "%d\n", published);
}
static DEVICE_ATTR_RO(published);
@ -95,8 +110,9 @@ static const struct attribute_group p2pmem_group = {
static void pci_p2pdma_release(void *data)
{
struct pci_dev *pdev = data;
struct pci_p2pdma *p2pdma = pdev->p2pdma;
struct pci_p2pdma *p2pdma;
p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
if (!p2pdma)
return;
@ -128,16 +144,14 @@ static int pci_p2pdma_setup(struct pci_dev *pdev)
if (error)
goto out_pool_destroy;
pdev->p2pdma = p2p;
error = sysfs_create_group(&pdev->dev.kobj, &p2pmem_group);
if (error)
goto out_pool_destroy;
rcu_assign_pointer(pdev->p2pdma, p2p);
return 0;
out_pool_destroy:
pdev->p2pdma = NULL;
gen_pool_destroy(p2p->pool);
out:
devm_kfree(&pdev->dev, p2p);
@ -159,6 +173,7 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
{
struct pci_p2pdma_pagemap *p2p_pgmap;
struct dev_pagemap *pgmap;
struct pci_p2pdma *p2pdma;
void *addr;
int error;
@ -200,7 +215,8 @@ int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar, size_t size,
goto pgmap_free;
}
error = gen_pool_add_owner(pdev->p2pdma->pool, (unsigned long)addr,
p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
error = gen_pool_add_owner(p2pdma->pool, (unsigned long)addr,
pci_bus_address(pdev, bar) + offset,
range_len(&pgmap->range), dev_to_node(&pdev->dev),
pgmap->ref);
@ -308,10 +324,41 @@ static const struct pci_p2pdma_whitelist_entry {
{}
};
static bool __host_bridge_whitelist(struct pci_host_bridge *host,
bool same_host_bridge)
/*
* This lookup function tries to find the PCI device corresponding to a given
* host bridge.
*
* It assumes the host bridge device is the first PCI device in the
* bus->devices list and that the devfn is 00.0. These assumptions should hold
* for all the devices in the whitelist above.
*
* This function is equivalent to pci_get_slot(host->bus, 0), however it does
* not take the pci_bus_sem lock seeing __host_bridge_whitelist() must not
* sleep.
*
* For this to be safe, the caller should hold a reference to a device on the
* bridge, which should ensure the host_bridge device will not be freed
* or removed from the head of the devices list.
*/
static struct pci_dev *pci_host_bridge_dev(struct pci_host_bridge *host)
{
struct pci_dev *root = pci_get_slot(host->bus, PCI_DEVFN(0, 0));
struct pci_dev *root;
root = list_first_entry_or_null(&host->bus->devices,
struct pci_dev, bus_list);
if (!root)
return NULL;
if (root->devfn != PCI_DEVFN(0, 0))
return NULL;
return root;
}
static bool __host_bridge_whitelist(struct pci_host_bridge *host,
bool same_host_bridge, bool warn)
{
struct pci_dev *root = pci_host_bridge_dev(host);
const struct pci_p2pdma_whitelist_entry *entry;
unsigned short vendor, device;
@ -320,7 +367,6 @@ static bool __host_bridge_whitelist(struct pci_host_bridge *host,
vendor = root->vendor;
device = root->device;
pci_dev_put(root);
for (entry = pci_p2pdma_whitelist; entry->vendor; entry++) {
if (vendor != entry->vendor || device != entry->device)
@ -331,6 +377,10 @@ static bool __host_bridge_whitelist(struct pci_host_bridge *host,
return true;
}
if (warn)
pci_warn(root, "Host bridge not in P2PDMA whitelist: %04x:%04x\n",
vendor, device);
return false;
}
@ -338,44 +388,90 @@ static bool __host_bridge_whitelist(struct pci_host_bridge *host,
* If we can't find a common upstream bridge take a look at the root
* complex and compare it to a whitelist of known good hardware.
*/
static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b)
static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b,
bool warn)
{
struct pci_host_bridge *host_a = pci_find_host_bridge(a->bus);
struct pci_host_bridge *host_b = pci_find_host_bridge(b->bus);
if (host_a == host_b)
return __host_bridge_whitelist(host_a, true);
return __host_bridge_whitelist(host_a, true, warn);
if (__host_bridge_whitelist(host_a, false) &&
__host_bridge_whitelist(host_b, false))
if (__host_bridge_whitelist(host_a, false, warn) &&
__host_bridge_whitelist(host_b, false, warn))
return true;
return false;
}
static enum pci_p2pdma_map_type
__upstream_bridge_distance(struct pci_dev *provider, struct pci_dev *client,
int *dist, bool *acs_redirects, struct seq_buf *acs_list)
static unsigned long map_types_idx(struct pci_dev *client)
{
return (pci_domain_nr(client->bus) << 16) |
(client->bus->number << 8) | client->devfn;
}
/*
* Calculate the P2PDMA mapping type and distance between two PCI devices.
*
* If the two devices are the same PCI function, return
* PCI_P2PDMA_MAP_BUS_ADDR and a distance of 0.
*
* If they are two functions of the same device, return
* PCI_P2PDMA_MAP_BUS_ADDR and a distance of 2 (one hop up to the bridge,
* then one hop back down to another function of the same device).
*
* In the case where two devices are connected to the same PCIe switch,
* return a distance of 4. This corresponds to the following PCI tree:
*
* -+ Root Port
* \+ Switch Upstream Port
* +-+ Switch Downstream Port 0
* + \- Device A
* \-+ Switch Downstream Port 1
* \- Device B
*
* The distance is 4 because we traverse from Device A to Downstream Port 0
* to the common Switch Upstream Port, back down to Downstream Port 1 and
* then to Device B. The mapping type returned depends on the ACS
* redirection setting of the ports along the path.
*
* If ACS redirect is set on any port in the path, traffic between the
* devices will go through the host bridge, so return
* PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; otherwise return
* PCI_P2PDMA_MAP_BUS_ADDR.
*
* Any two devices that have a data path that goes through the host bridge
* will consult a whitelist. If the host bridge is in the whitelist, return
* PCI_P2PDMA_MAP_THRU_HOST_BRIDGE with the distance set to the number of
* ports per above. If the device is not in the whitelist, return
* PCI_P2PDMA_MAP_NOT_SUPPORTED.
*/
static enum pci_p2pdma_map_type
calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client,
int *dist, bool verbose)
{
enum pci_p2pdma_map_type map_type = PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
struct pci_dev *a = provider, *b = client, *bb;
bool acs_redirects = false;
struct pci_p2pdma *p2pdma;
struct seq_buf acs_list;
int acs_cnt = 0;
int dist_a = 0;
int dist_b = 0;
int acs_cnt = 0;
char buf[128];
if (acs_redirects)
*acs_redirects = false;
seq_buf_init(&acs_list, buf, sizeof(buf));
/*
* Note, we don't need to take references to devices returned by
* pci_upstream_bridge() seeing we hold a reference to a child
* device which will already hold a reference to the upstream bridge.
*/
while (a) {
dist_b = 0;
if (pci_bridge_has_acs_redir(a)) {
seq_buf_print_bus_devfn(acs_list, a);
seq_buf_print_bus_devfn(&acs_list, a);
acs_cnt++;
}
@ -393,10 +489,8 @@ __upstream_bridge_distance(struct pci_dev *provider, struct pci_dev *client,
dist_a++;
}
if (dist)
*dist = dist_a + dist_b;
return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
*dist = dist_a + dist_b;
goto map_through_host_bridge;
check_b_path_acs:
bb = b;
@ -406,124 +500,45 @@ check_b_path_acs:
break;
if (pci_bridge_has_acs_redir(bb)) {
seq_buf_print_bus_devfn(acs_list, bb);
seq_buf_print_bus_devfn(&acs_list, bb);
acs_cnt++;
}
bb = pci_upstream_bridge(bb);
}
if (dist)
*dist = dist_a + dist_b;
*dist = dist_a + dist_b;
if (acs_cnt) {
if (acs_redirects)
*acs_redirects = true;
return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE;
if (!acs_cnt) {
map_type = PCI_P2PDMA_MAP_BUS_ADDR;
goto done;
}
return PCI_P2PDMA_MAP_BUS_ADDR;
}
static unsigned long map_types_idx(struct pci_dev *client)
{
return (pci_domain_nr(client->bus) << 16) |
(client->bus->number << 8) | client->devfn;
}
/*
* Find the distance through the nearest common upstream bridge between
* two PCI devices.
*
* If the two devices are the same device then 0 will be returned.
*
* If there are two virtual functions of the same device behind the same
* bridge port then 2 will be returned (one step down to the PCIe switch,
* then one step back to the same device).
*
* In the case where two devices are connected to the same PCIe switch, the
* value 4 will be returned. This corresponds to the following PCI tree:
*
* -+ Root Port
* \+ Switch Upstream Port
* +-+ Switch Downstream Port
* + \- Device A
* \-+ Switch Downstream Port
* \- Device B
*
* The distance is 4 because we traverse from Device A through the downstream
* port of the switch, to the common upstream port, back up to the second
* downstream port and then to Device B.
*
* Any two devices that cannot communicate using p2pdma will return
* PCI_P2PDMA_MAP_NOT_SUPPORTED.
*
* Any two devices that have a data path that goes through the host bridge
* will consult a whitelist. If the host bridges are on the whitelist,
* this function will return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE.
*
* If either bridge is not on the whitelist this function returns
* PCI_P2PDMA_MAP_NOT_SUPPORTED.
*
* If a bridge which has any ACS redirection bits set is in the path,
* acs_redirects will be set to true. In this case, a list of all infringing
* bridge addresses will be populated in acs_list (assuming it's non-null)
* for printk purposes.
*/
static enum pci_p2pdma_map_type
upstream_bridge_distance(struct pci_dev *provider, struct pci_dev *client,
int *dist, bool *acs_redirects, struct seq_buf *acs_list)
{
enum pci_p2pdma_map_type map_type;
map_type = __upstream_bridge_distance(provider, client, dist,
acs_redirects, acs_list);
if (map_type == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE) {
if (!cpu_supports_p2pdma() &&
!host_bridge_whitelist(provider, client))
map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
}
if (provider->p2pdma)
xa_store(&provider->p2pdma->map_types, map_types_idx(client),
xa_mk_value(map_type), GFP_KERNEL);
return map_type;
}
static enum pci_p2pdma_map_type
upstream_bridge_distance_warn(struct pci_dev *provider, struct pci_dev *client,
int *dist)
{
struct seq_buf acs_list;
bool acs_redirects;
int ret;
seq_buf_init(&acs_list, kmalloc(PAGE_SIZE, GFP_KERNEL), PAGE_SIZE);
if (!acs_list.buffer)
return -ENOMEM;
ret = upstream_bridge_distance(provider, client, dist, &acs_redirects,
&acs_list);
if (acs_redirects) {
if (verbose) {
acs_list.buffer[acs_list.len-1] = 0; /* drop final semicolon */
pci_warn(client, "ACS redirect is set between the client and provider (%s)\n",
pci_name(provider));
/* Drop final semicolon */
acs_list.buffer[acs_list.len-1] = 0;
pci_warn(client, "to disable ACS redirect for this path, add the kernel parameter: pci=disable_acs_redir=%s\n",
acs_list.buffer);
}
acs_redirects = true;
if (ret == PCI_P2PDMA_MAP_NOT_SUPPORTED) {
pci_warn(client, "cannot be used for peer-to-peer DMA as the client and provider (%s) do not share an upstream bridge or whitelisted host bridge\n",
pci_name(provider));
map_through_host_bridge:
if (!cpu_supports_p2pdma() &&
!host_bridge_whitelist(provider, client, acs_redirects)) {
if (verbose)
pci_warn(client, "cannot be used for peer-to-peer DMA as the client and provider (%s) do not share an upstream bridge or whitelisted host bridge\n",
pci_name(provider));
map_type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
}
kfree(acs_list.buffer);
return ret;
done:
rcu_read_lock();
p2pdma = rcu_dereference(provider->p2pdma);
if (p2pdma)
xa_store(&p2pdma->map_types, map_types_idx(client),
xa_mk_value(map_type), GFP_KERNEL);
rcu_read_unlock();
return map_type;
}
/**
@ -546,11 +561,11 @@ upstream_bridge_distance_warn(struct pci_dev *provider, struct pci_dev *client,
int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
int num_clients, bool verbose)
{
enum pci_p2pdma_map_type map;
bool not_supported = false;
struct pci_dev *pci_client;
int total_dist = 0;
int distance;
int i, ret;
int i, distance;
if (num_clients == 0)
return -1;
@ -564,16 +579,12 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients,
return -1;
}
if (verbose)
ret = upstream_bridge_distance_warn(provider,
pci_client, &distance);
else
ret = upstream_bridge_distance(provider, pci_client,
&distance, NULL, NULL);
map = calc_map_type_and_dist(provider, pci_client, &distance,
verbose);
pci_dev_put(pci_client);
if (ret == PCI_P2PDMA_MAP_NOT_SUPPORTED)
if (map == PCI_P2PDMA_MAP_NOT_SUPPORTED)
not_supported = true;
if (not_supported && !verbose)
@ -595,7 +606,15 @@ EXPORT_SYMBOL_GPL(pci_p2pdma_distance_many);
*/
bool pci_has_p2pmem(struct pci_dev *pdev)
{
return pdev->p2pdma && pdev->p2pdma->p2pmem_published;
struct pci_p2pdma *p2pdma;
bool res;
rcu_read_lock();
p2pdma = rcu_dereference(pdev->p2pdma);
res = p2pdma && p2pdma->p2pmem_published;
rcu_read_unlock();
return res;
}
EXPORT_SYMBOL_GPL(pci_has_p2pmem);
@ -675,6 +694,7 @@ void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size)
{
void *ret = NULL;
struct percpu_ref *ref;
struct pci_p2pdma *p2pdma;
/*
* Pairs with synchronize_rcu() in pci_p2pdma_release() to
@ -682,16 +702,16 @@ void *pci_alloc_p2pmem(struct pci_dev *pdev, size_t size)
* read-lock.
*/
rcu_read_lock();
if (unlikely(!pdev->p2pdma))
p2pdma = rcu_dereference(pdev->p2pdma);
if (unlikely(!p2pdma))
goto out;
ret = (void *)gen_pool_alloc_owner(pdev->p2pdma->pool, size,
(void **) &ref);
ret = (void *)gen_pool_alloc_owner(p2pdma->pool, size, (void **) &ref);
if (!ret)
goto out;
if (unlikely(!percpu_ref_tryget_live(ref))) {
gen_pool_free(pdev->p2pdma->pool, (unsigned long) ret, size);
gen_pool_free(p2pdma->pool, (unsigned long) ret, size);
ret = NULL;
goto out;
}
@ -710,8 +730,9 @@ EXPORT_SYMBOL_GPL(pci_alloc_p2pmem);
void pci_free_p2pmem(struct pci_dev *pdev, void *addr, size_t size)
{
struct percpu_ref *ref;
struct pci_p2pdma *p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
gen_pool_free_owner(pdev->p2pdma->pool, (uintptr_t)addr, size,
gen_pool_free_owner(p2pdma->pool, (uintptr_t)addr, size,
(void **) &ref);
percpu_ref_put(ref);
}
@ -725,9 +746,13 @@ EXPORT_SYMBOL_GPL(pci_free_p2pmem);
*/
pci_bus_addr_t pci_p2pmem_virt_to_bus(struct pci_dev *pdev, void *addr)
{
struct pci_p2pdma *p2pdma;
if (!addr)
return 0;
if (!pdev->p2pdma)
p2pdma = rcu_dereference_protected(pdev->p2pdma, 1);
if (!p2pdma)
return 0;
/*
@ -735,7 +760,7 @@ pci_bus_addr_t pci_p2pmem_virt_to_bus(struct pci_dev *pdev, void *addr)
* bus address as the physical address. So gen_pool_virt_to_phys()
* actually returns the bus address despite the misleading name.
*/
return gen_pool_virt_to_phys(pdev->p2pdma->pool, (unsigned long)addr);
return gen_pool_virt_to_phys(p2pdma->pool, (unsigned long)addr);
}
EXPORT_SYMBOL_GPL(pci_p2pmem_virt_to_bus);
@ -806,19 +831,40 @@ EXPORT_SYMBOL_GPL(pci_p2pmem_free_sgl);
*/
void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
{
if (pdev->p2pdma)
pdev->p2pdma->p2pmem_published = publish;
struct pci_p2pdma *p2pdma;
rcu_read_lock();
p2pdma = rcu_dereference(pdev->p2pdma);
if (p2pdma)
p2pdma->p2pmem_published = publish;
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct pci_dev *provider,
struct pci_dev *client)
static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
struct device *dev)
{
enum pci_p2pdma_map_type type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
struct pci_dev *provider = to_p2p_pgmap(pgmap)->provider;
struct pci_dev *client;
struct pci_p2pdma *p2pdma;
if (!provider->p2pdma)
return PCI_P2PDMA_MAP_NOT_SUPPORTED;
return xa_to_value(xa_load(&provider->p2pdma->map_types,
map_types_idx(client)));
if (!dev_is_pci(dev))
return PCI_P2PDMA_MAP_NOT_SUPPORTED;
client = to_pci_dev(dev);
rcu_read_lock();
p2pdma = rcu_dereference(provider->p2pdma);
if (p2pdma)
type = xa_to_value(xa_load(&p2pdma->map_types,
map_types_idx(client)));
rcu_read_unlock();
return type;
}
static int __pci_p2pdma_map_sg(struct pci_p2pdma_pagemap *p2p_pgmap,
@ -853,14 +899,8 @@ int pci_p2pdma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
{
struct pci_p2pdma_pagemap *p2p_pgmap =
to_p2p_pgmap(sg_page(sg)->pgmap);
struct pci_dev *client;
if (WARN_ON_ONCE(!dev_is_pci(dev)))
return 0;
client = to_pci_dev(dev);
switch (pci_p2pdma_map_type(p2p_pgmap->provider, client)) {
switch (pci_p2pdma_map_type(sg_page(sg)->pgmap, dev)) {
case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
return dma_map_sg_attrs(dev, sg, nents, dir, attrs);
case PCI_P2PDMA_MAP_BUS_ADDR:
@ -884,17 +924,9 @@ EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg_attrs);
void pci_p2pdma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction dir, unsigned long attrs)
{
struct pci_p2pdma_pagemap *p2p_pgmap =
to_p2p_pgmap(sg_page(sg)->pgmap);
enum pci_p2pdma_map_type map_type;
struct pci_dev *client;
if (WARN_ON_ONCE(!dev_is_pci(dev)))
return;
client = to_pci_dev(dev);
map_type = pci_p2pdma_map_type(p2p_pgmap->provider, client);
map_type = pci_p2pdma_map_type(sg_page(sg)->pgmap, dev);
if (map_type == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE)
dma_unmap_sg_attrs(dev, sg, nents, dir, attrs);

2
include/linux/pci.h
View File

@ -497,7 +497,7 @@ struct pci_dev {
u16 pasid_features;
#endif
#ifdef CONFIG_PCI_P2PDMA
struct pci_p2pdma *p2pdma;
struct pci_p2pdma __rcu *p2pdma;
#endif
u16 acs_cap; /* ACS Capability offset */
phys_addr_t rom; /* Physical address if not from BAR */