Re: [Xen-devel] [PATCH v3 3/3] OvmfPkg/XenSupport: turn off address decoding before BAR sizing

[Laszlo Ersek <lersek@xxxxxxxxxx>]

On 04/25/19 22:23, Igor Druzhinin wrote:
> On Xen, hvmloader firmware leaves address decoding enabled for
> enumerated PCI device before jumping into OVMF. OVMF seems to
> expect it to be disabled and tries to size PCI BARs in several places
> without disabling it which causes BAR64, for example, being
> incorrectly placed by QEMU.
> 
> Fix it by disabling PCI address decoding explicitly before the
> first attempt to size BARs on Xen.
> 
> Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
> ---
> Changes in v3:
> - dropped unused arguments and rename PcatPciRootBridgeDecoding function
> - make mask application more clear as suggested
> ---
>  OvmfPkg/Library/PciHostBridgeLib/XenSupport.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c 
> b/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c
> index 76fca53..b41bd6b 100644
> --- a/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c
> +++ b/OvmfPkg/Library/PciHostBridgeLib/XenSupport.c
> @@ -49,6 +49,22 @@ PcatPciRootBridgeBarExisted (
>    EnableInterrupts ();
>  }
>  
> +#define PCI_COMMAND_DECODE ((UINT16)(EFI_PCI_COMMAND_IO_SPACE | \
> +                                     EFI_PCI_COMMAND_MEMORY_SPACE))
> +STATIC
> +VOID
> +PcatPciRootBridgeDecodingDisable (
> +  IN  UINTN                          Address
> +  )
> +{
> +  UINT16                             Value;
> +
> +  Value = PciRead16 (Address);
> +  if (Value & PCI_COMMAND_DECODE) {
> +    PciWrite16 (Address, Value & ~(UINT32)PCI_COMMAND_DECODE);
> +  }
> +}
> +
>  STATIC
>  VOID
>  PcatPciRootBridgeParseBars (
> @@ -75,6 +91,11 @@ PcatPciRootBridgeParseBars (
>    UINT64                            Limit;
>    PCI_ROOT_BRIDGE_APERTURE          *MemAperture;
>  
> +  // Disable address decoding for every device before OVMF starts sizing it
> +  PcatPciRootBridgeDecodingDisable (
> +    PCI_LIB_ADDRESS (Bus, Device, Function, PCI_COMMAND_OFFSET)
> +  );
> +
>    for (Offset = BarOffsetBase; Offset < BarOffsetEnd; Offset += sizeof 
> (UINT32)) {
>      PcatPciRootBridgeBarExisted (
>        PCI_LIB_ADDRESS (Bus, Device, Function, Offset),
> 

Acked-by: Laszlo Ersek <lersek@xxxxxxxxxx>

Someone from the Xen community please ACK this too, and then we can push
the series.

Thanks,
Laszlo

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