Re: [edk2-devel] [PATCH 0/4] OvmfPkg/PlatformPei: fix two assertion failures with weird RAM sizes

["Laszlo Ersek" <lersek@redhat.com>]

On 05/04/19 02:07, Laszlo Ersek wrote:
> Repo:   https://github.com/lersek/edk2.git
> Branch: exbar_mtrr_rhbz_1666941
> Ref:    https://bugzilla.redhat.com/show_bug.cgi?id=1666941
> Ref:    https://bugzilla.redhat.com/show_bug.cgi?id=1701710
> 
> When booting OVMF on QEMU with "weird" RAM sizes, QEMU's low-RAM split
> logic can trigger two assertion failures in OVMF:
> 
> - conflict between PCIEXBAR (ECAM) and low-RAM, on q35,
> 
> - running out of variable MTRRs when marking the uncacheable MMIO range
>   in 32-bit address space, on both i440fx and q35.
> 
> This series fixes both issues, by moving around the PCIEXBAR on q35, and
> by truncating the size of the uncacheable 32-bit area to a power of two.
> The latter idea was inspired by SeaBIOS.
> 
> Tested on both machine types, with the following memory sizes (all in
> MB): 1025, 2815, 3583, 5120. On i440fx, the X64 build was used (without
> SMM). On q35, the IA32 and IA32X64 builds were used (with SMM). Testing
> included "/proc/mtrr" verification, 32-bit PCI MMIO aperture
> verification, general dmesg checks, and my usual regression tests too
> (ACPI S3, UEFI variable services, ...).

Thanks to everyone for the feedback!

I've now pushed this series as commit range 3b7a897cd8e3..39b9a5ffe661,
with the following updates (all requested per review feedback):

* added the following tag to every commit message:

  Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1814

* dropped the following tag from every affected commit message (i.e., on
  the first three patches):

  Contributed-under: TianoCore Contribution Agreement 1.1

* picked up Phil's and Ard's R-bs

* replaced "hole" with "window" in the commit message of patch #3, then
  re-folded the text to 74 columns.

Cheers
Laszlo

> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> 
> Thanks
> Laszlo
> 
> Laszlo Ersek (4):
>   OvmfPkg/PlatformPei: assign PciSize on both i440fx/q35 branches
>     explicitly
>   OvmfPkg/PlatformPei: hoist PciBase assignment above the i440fx/q35
>     branching
>   OvmfPkg/PlatformPei: reorder the 32-bit PCI hole vs. the PCIEXBAR on
>     q35
>   OvmfPkg/PlatformPei: fix MTRR for low-RAM sizes that have many bits
>     clear
> 
>  OvmfPkg/OvmfPkgIa32.dsc         |  5 +----
>  OvmfPkg/OvmfPkgIa32X64.dsc      |  5 +----
>  OvmfPkg/OvmfPkgX64.dsc          |  5 +----
>  OvmfPkg/PlatformPei/MemDetect.c | 23 +++++++++++++++++---
>  OvmfPkg/PlatformPei/Platform.c  | 14 +++++-------
>  OvmfPkg/PlatformPei/Platform.h  |  2 ++
>  6 files changed, 31 insertions(+), 23 deletions(-)
>