Re: [edk2-devel] [PATCH for-edk2-stable201905 4/6] Revert "OvmfPkg/PlatformPei: assign PciSize on both i440fx/q35 branches explicitly"

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 5/29/19 5:12 PM, Laszlo Ersek wrote:
> This reverts commit 60e95bf5094fbb9b728729ccfaf32184b3662317.
> 
> The original fix for <https://bugzilla.tianocore.org/show_bug.cgi?id=1814>
> triggered a bug / incorrect assumption in QEMU.
> 
> QEMU assumes that the PCIEXBAR is below the 32-bit PCI window, not above
> it. When the firmware doesn't satisfy this assumption, QEMU generates an
> \_SB.PCI0._CRS object in the ACPI DSDT that does not reflect the
> firmware's 32-bit MMIO BAR assignments. This causes OSes to re-assign
> 32-bit MMIO BARs.
> 
> Working around the problem in the firmware looks less problematic than
> fixing QEMU. Revert the original changes first, before implementing an
> alternative fix.
> 
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1859
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>

Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>

> ---
>  OvmfPkg/PlatformPei/Platform.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
> index 5e0a15484230..0876316eefbc 100644
> --- a/OvmfPkg/PlatformPei/Platform.c
> +++ b/OvmfPkg/PlatformPei/Platform.c
> @@ -190,10 +190,8 @@ MemMapInitialization (
>        ASSERT (TopOfLowRam <= PciExBarBase);
>        ASSERT (PciExBarBase <= MAX_UINT32 - SIZE_256MB);
>        PciBase = (UINT32)(PciExBarBase + SIZE_256MB);
> -      PciSize = 0xFC000000 - PciBase;
>      } else {
>        PciBase = (TopOfLowRam < BASE_2GB) ? BASE_2GB : TopOfLowRam;
> -      PciSize = 0xFC000000 - PciBase;
>      }
>  
>      //
> @@ -209,6 +207,7 @@ MemMapInitialization (
>      // 0xFED20000    gap                          896 KB
>      // 0xFEE00000    LAPIC                          1 MB
>      //
> +    PciSize = 0xFC000000 - PciBase;
>      AddIoMemoryBaseSizeHob (PciBase, PciSize);
>      PcdStatus = PcdSet64S (PcdPciMmio32Base, PciBase);
>      ASSERT_RETURN_ERROR (PcdStatus);
>