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[PATCH v11 17/17] arm/vpci: honor access size when returning an error
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Date: Sat, 2 Dec 2023 01:27:07 +0000
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- Cc: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Delivery-date: Sat, 02 Dec 2023 01:27:37 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHaJL6qzrPLCvUkHkyTdIPsJJSlOA==
- Thread-topic: [PATCH v11 17/17] arm/vpci: honor access size when returning an error
Guest can try to read config space using different access sizes: 8,
16, 32, 64 bits. We need to take this into account when we are
returning an error back to MMIO handler, otherwise it is possible to
provide more data than requested: i.e. guest issues LDRB instruction
to read one byte, but we are writing 0xFFFFFFFFFFFFFFFF in the target
register.
Signed-off-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
---
xen/arch/arm/vpci.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/vpci.c b/xen/arch/arm/vpci.c
index b6ef440f17..05a479096e 100644
--- a/xen/arch/arm/vpci.c
+++ b/xen/arch/arm/vpci.c
@@ -42,6 +42,8 @@ static int vpci_mmio_read(struct vcpu *v, mmio_info_t *info,
{
struct pci_host_bridge *bridge = p;
pci_sbdf_t sbdf;
+ const uint8_t access_size = (1 << info->dabt.size) * 8;
+ const uint64_t access_mask = GENMASK_ULL(access_size - 1, 0);
/* data is needed to prevent a pointer cast on 32bit */
unsigned long data;
@@ -49,7 +51,7 @@ static int vpci_mmio_read(struct vcpu *v, mmio_info_t *info,
if ( !vpci_sbdf_from_gpa(v->domain, bridge, info->gpa, &sbdf) )
{
- *r = ~0UL;
+ *r = access_mask;
return 1;
}
@@ -60,7 +62,7 @@ static int vpci_mmio_read(struct vcpu *v, mmio_info_t *info,
return 1;
}
- *r = ~0UL;
+ *r = access_mask;
return 0;
}
--
2.42.0
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