[PATCH 2/5] pci-assign: Fix dword read at PCI_COMMAND

[Jan Kiszka <jan.kiszka@xxxxxx>]

From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>

If we emulate the command register, we must only read its content from
the shadow config space. For dword read of both PCI_COMMAND and
PCI_STATUS, at least the latter must be read from the device.

For simplicity reasons and as the code path is not considered
performance critical for the affected SRIOV devices, the fix performes
device access to the command word unconditionally, even if emulation is
enabled and only that word is read.

Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
 hw/device-assignment.c |   14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/hw/device-assignment.c b/hw/device-assignment.c
index bc3a57b..6ff1456 100644
--- a/hw/device-assignment.c
+++ b/hw/device-assignment.c
@@ -494,14 +494,11 @@ static uint32_t assigned_dev_pci_read_config(PCIDevice *d, uint32_t address,
     /*
      * Catch access to
      *  - vendor & device ID
-     *  - command register (if emulation needed)
      *  - base address registers
      *  - ROM base address & capability pointer
      *  - interrupt line & pin
      */
     if (ranges_overlap(address, len, PCI_VENDOR_ID, 4) ||
-        (pci_dev->need_emulate_cmd &&
-         ranges_overlap(address, len, PCI_COMMAND, 2)) ||
         ranges_overlap(address, len, PCI_BASE_ADDRESS_0, 24) ||
         ranges_overlap(address, len, PCI_ROM_ADDRESS, 8) ||
         ranges_overlap(address, len, PCI_INTERRUPT_LINE, 2)) {
@@ -533,6 +530,17 @@ do_log:
     DEBUG("(%x.%x): address=%04x val=0x%08x len=%d\n",
           (d->devfn >> 3) & 0x1F, (d->devfn & 0x7), address, val, len);
 
+    if (pci_dev->need_emulate_cmd &&
+        ranges_overlap(address, len, PCI_COMMAND, 2)) {
+        if (address == PCI_COMMAND) {
+            val &= 0xffff0000;
+            val |= pci_default_read_config(d, PCI_COMMAND, 2);
+        } else {
+            /* high-byte access */
+            val = pci_default_read_config(d, PCI_COMMAND+1, 1);
+        }
+    }
+
     if (!pci_dev->cap.available) {
         /* kill the special capabilities */
         if (address == PCI_COMMAND && len == 4) {
-- 
1.7.1

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