[edk2-devel] [PATCH 1/1] UefiCpuPkg/MpInitLib: Reduce reset vector memory pressure
Ni, Ray
ray.ni at intel.com
Wed Sep 23 03:08:44 UTC 2020
It's a good optimization.
Can you eliminate the GetApResetStackSize() and embed the check and calculation in GetApResetVectorSize()?
Reason: GetApResetStackSize() is only called in one place. Removing the additional layer of function call makes
the code easier to read.
Thanks,
Ray
> -----Original Message-----
> From: Tom Lendacky <thomas.lendacky at amd.com>
> Sent: Wednesday, September 23, 2020 3:59 AM
> To: devel at edk2.groups.io
> Cc: Dong, Eric <eric.dong at intel.com>; Ni, Ray <ray.ni at intel.com>; Laszlo Ersek
> <lersek at redhat.com>; Kumar, Rahul1 <rahul1.kumar at intel.com>; Brijesh
> Singh <brijesh.singh at amd.com>; Garrett Kirkendall
> <garrett.kirkendall at amd.com>
> Subject: [PATCH 1/1] UefiCpuPkg/MpInitLib: Reduce reset vector memory
> pressure
>
> From: Tom Lendacky <thomas.lendacky at amd.com>
>
> The AP reset vector stack allocation is only required if running as an
> SEV-ES guest. Since the reset vector allocation is below 1MB in memory,
> eliminate the requirement for bare-metal systems and non SEV-ES guests
> to allocate the extra stack area, which can be large if the
> PcdCpuMaxLogicalProcessorNumber value is large.
>
> Cc: Garrett Kirkendall <garrett.kirkendall at amd.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky at amd.com>
> ---
> UefiCpuPkg/Library/MpInitLib/MpLib.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> index 07426274f639..39af2f9fba7d 100644
> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.c
> @@ -1152,7 +1152,15 @@ GetApResetStackSize (
> VOID
> )
> {
> - return AP_RESET_STACK_SIZE *
> PcdGet32(PcdCpuMaxLogicalProcessorNumber);
> + //
> + // The AP reset stack is only used by SEV-ES guests. Don't add to the
> + // allocation if not necessary.
> + //
> + if (PcdGetBool (PcdSevEsIsEnabled) == TRUE) {
> + return AP_RESET_STACK_SIZE *
> PcdGet32(PcdCpuMaxLogicalProcessorNumber);
> + } else {
> + return 0;
> + }
> }
>
> /**
> --
> 2.28.0
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