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);
>
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