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Subject[RFC v5 4/7] PCI: Add support for enforcing all MMIO BARs to be page aligned
Date
When vfio passthrough a PCI device of which MMIO
BARs are smaller than PAGE_SIZE, guest will not
handle the mmio accesses to the BARs which leads
to mmio emulations in host.

This is because vfio will not allow to passthrough
one BAR's mmio page which may be shared with other
BARs. Otherwise, there will be a backdoor that
guest can use to access BARs of other guest.

To solve this issue, this patch modifies
resource_alignment to support syntax where
multiple devices get the same alignment. So we
can use something like
"pci=resource_alignment=*:*:*.*:noresize" to
enforce the alignment of all MMIO BARs to be at
least PAGE_SIZE so that one BAR's mmio page would
not be shared with other BARs.

And we also define a macro PCIBIOS_MIN_ALIGNMENT
to enable this automatically on PPC64 platform
which can easily hit this issue because its
PAGE_SIZE is 64KB.

Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com>
---
Documentation/kernel-parameters.txt | 2 ++
arch/powerpc/include/asm/pci.h | 2 ++
drivers/pci/pci.c | 64 +++++++++++++++++++++++++++++------
3 files changed, 57 insertions(+), 11 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index d8b29ab..542be4a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2918,6 +2918,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
aligned memory resources.
If <order of align> is not specified,
PAGE_SIZE is used as alignment.
+ <domain>, <bus>, <slot> and <func> can be set to
+ "*" which means match all values.
PCI-PCI bridge can be specified, if resource
windows need to be expanded.
noresize: Don't change the resources' sizes when
diff --git a/arch/powerpc/include/asm/pci.h b/arch/powerpc/include/asm/pci.h
index 6f8065a..78f230f 100644
--- a/arch/powerpc/include/asm/pci.h
+++ b/arch/powerpc/include/asm/pci.h
@@ -30,6 +30,8 @@
#define PCIBIOS_MIN_IO 0x1000
#define PCIBIOS_MIN_MEM 0x10000000

+#define PCIBIOS_MIN_ALIGNMENT PAGE_SIZE
+
struct pci_dev;

/* Values for the `which' argument to sys_pciconfig_iobase syscall. */
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 7271ce3..b690bc9 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -4605,7 +4605,12 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
int seg, bus, slot, func, align_order, count;
resource_size_t align = 0;
char *p;
+ bool invalid = false;

+#ifdef PCIBIOS_MIN_ALIGNMENT
+ align = PCIBIOS_MIN_ALIGNMENT;
+ *resize = false;
+#endif
spin_lock(&resource_alignment_lock);
p = resource_alignment_param;
while (*p) {
@@ -4622,16 +4627,49 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
} else {
align_order = -1;
}
- if (sscanf(p, "%x:%x:%x.%x%n",
- &seg, &bus, &slot, &func, &count) != 4) {
+ if (p[0] == '*' && p[1] == ':') {
+ seg = -1;
+ count = 1;
+ } else if (sscanf(p, "%x%n", &seg, &count) != 1 ||
+ p[count] != ':') {
+ invalid = true;
+ break;
+ }
+ p += count + 1;
+ if (*p == '*') {
+ bus = -1;
+ count = 1;
+ } else if (sscanf(p, "%x%n", &bus, &count) != 1) {
+ invalid = true;
+ break;
+ }
+ p += count;
+ if (*p == '.') {
+ slot = bus;
+ bus = seg;
seg = 0;
- if (sscanf(p, "%x:%x.%x%n",
- &bus, &slot, &func, &count) != 3) {
- /* Invalid format */
- printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: %s\n",
- p);
+ p++;
+ } else if (*p == ':') {
+ p++;
+ if (p[0] == '*' && p[1] == '.') {
+ slot = -1;
+ count = 1;
+ } else if (sscanf(p, "%x%n", &slot, &count) != 1 ||
+ p[count] != '.') {
+ invalid = true;
break;
}
+ p += count + 1;
+ } else {
+ invalid = true;
+ break;
+ }
+ if (*p == '*') {
+ func = -1;
+ count = 1;
+ } else if (sscanf(p, "%x%n", &func, &count) != 1) {
+ invalid = true;
+ break;
}
p += count;
if (!strncmp(p, ":noresize", 9)) {
@@ -4639,10 +4677,10 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
p += 9;
} else
*resize = true;
- if (seg == pci_domain_nr(dev->bus) &&
- bus == dev->bus->number &&
- slot == PCI_SLOT(dev->devfn) &&
- func == PCI_FUNC(dev->devfn)) {
+ if ((seg == pci_domain_nr(dev->bus) || seg == -1) &&
+ (bus == dev->bus->number || bus == -1) &&
+ (slot == PCI_SLOT(dev->devfn) || slot == -1) &&
+ (func == PCI_FUNC(dev->devfn) || func == -1)) {
if (align_order == -1)
align = PAGE_SIZE;
else
@@ -4652,10 +4690,14 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
}
if (*p != ';' && *p != ',') {
/* End of param or invalid format */
+ invalid = true;
break;
}
p++;
}
+ if (invalid == true)
+ printk(KERN_ERR "PCI: Can't parse resource_alignment parameter:%s\n",
+ p);
spin_unlock(&resource_alignment_lock);
return align;
}
--
1.7.9.5
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