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author | Laszlo Ersek <lersek@redhat.com> | 2015-06-26 16:09:52 +0000 |
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committer | lersek <lersek@Edk2> | 2015-06-26 16:09:52 +0000 |
commit | 79d274b8b6b113248661c18f31c4be03c7da32de (patch) | |
tree | 9e4f806a8628eac70c518160d858015350e7f490 /MdeModulePkg/Universal/DisplayEngineDxe/ProcessOptions.c | |
parent | cfc80e2e95ee639e240c09eaeab76c0286bf917e (diff) | |
download | edk2-platforms-79d274b8b6b113248661c18f31c4be03c7da32de.tar.xz |
OvmfPkg: PlatformPei: invert MTRR setup in QemuInitializeRam()
At the moment we work with a UC default MTRR type, and set three memory
ranges to WB:
- [0, 640 KB),
- [1 MB, LowerMemorySize),
- [4 GB, 4 GB + UpperMemorySize).
Unfortunately, coverage for the third range can fail with a high
likelihood. If the alignment of the base (ie. 4 GB) and the alignment of
the size (UpperMemorySize) differ, then MtrrLib creates a series of
variable MTRR entries, with power-of-two sized MTRR masks. And, it's
really easy to run out of variable MTRR entries, dependent on the
alignment difference.
This is a problem because a Linux guest will loudly reject any high memory
that is not covered my MTRR.
So, let's follow the inverse pattern (loosely inspired by SeaBIOS):
- flip the MTRR default type to WB,
- set [0, 640 KB) to WB -- fixed MTRRs have precedence over the default
type and variable MTRRs, so we can't avoid this,
- set [640 KB, 1 MB) to UC -- implemented with fixed MTRRs,
- set [LowerMemorySize, 4 GB) to UC -- should succeed with variable MTRRs
more likely than the other scheme (due to less chaotic alignment
differences).
Effects of this patch can be observed by setting DEBUG_CACHE (0x00200000)
in PcdDebugPrintErrorLevel.
Cc: Maoming <maoming.maoming@huawei.com>
Cc: Huangpeng (Peter) <peter.huangpeng@huawei.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Maoming <maoming.maoming@huawei.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17722 6f19259b-4bc3-4df7-8a09-765794883524
Diffstat (limited to 'MdeModulePkg/Universal/DisplayEngineDxe/ProcessOptions.c')
0 files changed, 0 insertions, 0 deletions