[Xen-devel] [PATCH] x86/hvmloader: align BAR position to 4K

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

When placing BARs with sizes smaller than 4K multiple BARs can end
up mapped to the same guest physical address, and thus won't work
correctly.

Align all BARs placement to 4K in hvmloader to prevent such
overlapping.

Note that the guest can still move the BARs around and create this
collisions, and that BARs not filling up a physical page might leak
access to other MMIO regions placed in the same host physical page.

This is however no worse than what's currently done, and hence should
be considered an improvement over the current state.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 tools/firmware/hvmloader/pci.c  | 4 ++++
 tools/firmware/hvmloader/util.h | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/tools/firmware/hvmloader/pci.c b/tools/firmware/hvmloader/pci.c
index 0b708bf578..c433b34cd6 100644
--- a/tools/firmware/hvmloader/pci.c
+++ b/tools/firmware/hvmloader/pci.c
@@ -489,6 +489,10 @@ void pci_setup(void)
 
         resource->base = base;
 
+        if ( (bar_data & PCI_BASE_ADDRESS_SPACE) ==
+             PCI_BASE_ADDRESS_SPACE_MEMORY )
+            resource->base = ROUNDUP(resource->base, PAGE_SIZE);
+
         pci_writel(devfn, bar_reg, bar_data);
         if (using_64bar)
             pci_writel(devfn, bar_reg + 4, bar_data_upper);
diff --git a/tools/firmware/hvmloader/util.h b/tools/firmware/hvmloader/util.h
index 7bca6418d2..b5554b5844 100644
--- a/tools/firmware/hvmloader/util.h
+++ b/tools/firmware/hvmloader/util.h
@@ -51,6 +51,8 @@ void __bug(char *file, int line) __attribute__((noreturn));
 #define MB(mb) (mb##ULL << 20)
 #define GB(gb) (gb##ULL << 30)
 
+#define ROUNDUP(x, a) (((x) + (a) - 1) & ~((a) - 1))
+
 static inline int test_bit(unsigned int b, const void *p)
 {
     return !!(((const uint8_t *)p)[b>>3] & (1u<<(b&7)));
-- 
2.24.1


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