On 5/8/20 2:16 PM, Laszlo Ersek wrote:
In commit d42fdd6f8384 ("OvmfPkg: improve SMM comms security with adaptive MemoryTypeInformation", 2020-03-12), we enabled the boot-to-boot tracking of the usages of various UEFI memory types.Both whitepapers listed in that commit recommend that BS Code/Data type memory *not* be tracked. This recommendation was confirmed by Jiewen in the following two messages as well: [1] https://edk2.groups.io/g/devel/message/55741 http://mid.mail-archive.com/74D8A39837DF1E4DA445A8C0B3885C503F97B579@shsmsx102.ccr.corp.intel.com [2] https://edk2.groups.io/g/devel/message/55749 http://mid.mail-archive.com/74D8A39837DF1E4DA445A8C0B3885C503F97BDC5@shsmsx102.ccr.corp.intel.com While tracking BS Code/Data type memory has one benefit (it de-fragments the UEFI memory map), the downsides outweigh it. Spikes in BS Data type memory usage are not uncommon in particular, and they may have the following consequences: - such reboots during normal boot that look "spurious" to the end user, and have no SMM security benefit, - a large BS Data record in MemoryTypeInformation may cause issues when the DXE Core tries to prime the according bin(s), but the system's RAM size has been reduced meanwhile. Removing the BS Code/Data entries from MemoryTypeInformation leads to a bit more fragmentation in the UEFI memory map, but that should be harmless. Cc: Ard Biesheuvel <ard.biesheu...@arm.com> Cc: Jiewen Yao <jiewen....@intel.com> Cc: Jordan Justen <jordan.l.jus...@intel.com> Cc: Philippe Mathieu-Daudé <phi...@redhat.com> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2706 Signed-off-by: Laszlo Ersek <ler...@redhat.com> --- OvmfPkg/PlatformPei/MemTypeInfo.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/OvmfPkg/PlatformPei/MemTypeInfo.c b/OvmfPkg/PlatformPei/MemTypeInfo.c index 863c6f382680..8100a2db7d44 100644 --- a/OvmfPkg/PlatformPei/MemTypeInfo.c +++ b/OvmfPkg/PlatformPei/MemTypeInfo.c @@ -31,8 +31,6 @@ STATIC EFI_MEMORY_TYPE_INFORMATION mDefaultMemoryTypeInformation[] = { { EfiReservedMemoryType, 0x004 }, { EfiRuntimeServicesData, 0x024 }, { EfiRuntimeServicesCode, 0x030 }, - { EfiBootServicesCode, 0x180 }, - { EfiBootServicesData, 0xF00 }, { EfiMaxMemoryType, 0x000 } };
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