[PATCH] xen/arm: fix SBDF calculation for vPCI MMIO handlers

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

While in vPCI MMIO trap handlers for the guest PCI host bridge it is not
enough for SBDF translation to simply call VPCI_ECAM_BDF(info->gpa) as
the base address may not be aligned in the way that the translation
always work. If not adjusted with respect to the base address it may not be
able to properly convert SBDF and crashes:

(XEN) vpci_mmio_read 0000:65:1a.0 reg 8bc gpa e65d08bc
(XEN) Data Abort Trap. Syndrome=0x6
(XEN) Walking Hypervisor VA 0x467a28bc on CPU0 via TTBR 0x00000000481d5000

Fix this by adjusting the gpa with respect to the host bridge base address
in a way as it is done for x86.

Fixes: d59168dc05a5 ("xen/arm: Enable the existing x86 virtual PCI support for 
ARM")

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
---
 xen/arch/arm/vpci.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/vpci.c b/xen/arch/arm/vpci.c
index 8f40a0dec6d2..23f45386f4b3 100644
--- a/xen/arch/arm/vpci.c
+++ b/xen/arch/arm/vpci.c
@@ -24,7 +24,7 @@ static int vpci_mmio_read(struct vcpu *v, mmio_info_t *info,
     unsigned long data;
 
     /* We ignore segment part and always handle segment 0 */
-    sbdf.sbdf = VPCI_ECAM_BDF(info->gpa);
+    sbdf.sbdf = VPCI_ECAM_BDF(info->gpa - GUEST_VPCI_ECAM_BASE);
 
     if ( vpci_ecam_read(sbdf, ECAM_REG_OFFSET(info->gpa),
                         1U << info->dabt.size, &data) )
@@ -44,7 +44,7 @@ static int vpci_mmio_write(struct vcpu *v, mmio_info_t *info,
     pci_sbdf_t sbdf;
 
     /* We ignore segment part and always handle segment 0 */
-    sbdf.sbdf = VPCI_ECAM_BDF(info->gpa);
+    sbdf.sbdf = VPCI_ECAM_BDF(info->gpa - GUEST_VPCI_ECAM_BASE);
 
     return vpci_ecam_write(sbdf, ECAM_REG_OFFSET(info->gpa),
                            1U << info->dabt.size, r);
-- 
2.25.1