Re: [Qemu-devel] [PATCH] msix: fix msix_vector_masked

[Stefano Stabellini]

On Sat, 13 Feb 2016, Michael S. Tsirkin wrote:
> commit 428c3ece97179557f2753071fb0ca97a03437267 ("fix MSI injection on Xen")
> inadvertently enabled the xen-specific logic unconditionally.
> Limit it to only when xen is enabled.
> Additionally, msix data should be read with pci_get_log
> since the format is pci little-endian.
> 
> Reported-by: "Daniel P. Berrange" <address@hidden>
> Cc: Stefano Stabellini <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>

Thanks Daniel for finding the issue and thanks Michael for fixing my
bug, sorry about that.


>  hw/pci/msix.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/pci/msix.c b/hw/pci/msix.c
> index eb4ef11..537fdba 100644
> --- a/hw/pci/msix.c
> +++ b/hw/pci/msix.c
> @@ -80,10 +80,10 @@ static void msix_clr_pending(PCIDevice *dev, int vector)
>  static bool msix_vector_masked(PCIDevice *dev, unsigned int vector, bool 
> fmask)
>  {
>      unsigned offset = vector * PCI_MSIX_ENTRY_SIZE;
> -    uint32_t *data = (uint32_t *)&dev->msix_table[offset + 
> PCI_MSIX_ENTRY_DATA];
> +    uint8_t *data = &dev->msix_table[offset + PCI_MSIX_ENTRY_DATA];
>      /* MSIs on Xen can be remapped into pirqs. In those cases, masking
>       * and unmasking go through the PV evtchn path. */
> -    if (xen_is_pirq_msi(*data)) {
> +    if (xen_enabled() && xen_is_pirq_msi(pci_get_long(data))) {
>          return false;
>      }
>      return fmask || dev->msix_table[offset + PCI_MSIX_ENTRY_VECTOR_CTRL] &

I think this is good, but moving the xen_enabled() check inside
xen_is_pirq_msi is even be better, so that we cover all call sites at
once.


diff --git a/xen-hvm.c b/xen-hvm.c
index 039680a..991f6b7 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -151,7 +151,8 @@ int xen_is_pirq_msi(uint32_t msi_data)
     /* If vector is 0, the msi is remapped into a pirq, passed as
      * dest_id.
      */
-    return ((msi_data & MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT) == 0;
+    return xen_enabled() &&
+        ((msi_data & MSI_DATA_VECTOR_MASK) >> MSI_DATA_VECTOR_SHIFT) == 0;
 }
 
 void xen_hvm_inject_msi(uint64_t addr, uint32_t data)