(CC Jeff)
Sorry about the delay.
I have some light comments below; I expect at least a few of them to be
incorrect :)
On 12/29/17 09:36, Jian J Wang wrote:
> The reason is that DXE part initialization will reuse the stack allocated
> at PEI phase, if MP was initialized before. Some code added to check this
> situation and use stack base address saved in HOB passed from PEI.
>
> Cc: Jiewen Yao <jiewen....@intel.com>
> Cc: Eric Dong <eric.d...@intel.com>
> Cc: Laszlo Ersek <ler...@redhat.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Jian J Wang <jian.j.w...@intel.com>
> ---
> UefiCpuPkg/Library/MpInitLib/DxeMpLib.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> index 40c1bf407a..05484c9ff3 100644
> --- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> +++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
> @@ -295,6 +295,7 @@ InitMpGlobalData (
> UINTN Index;
> EFI_GCD_MEMORY_SPACE_DESCRIPTOR MemDesc;
> UINTN StackBase;
> + CPU_INFO_IN_HOB *CpuInfoInHob;
>
> SaveCpuMpData (CpuMpData);
>
> @@ -314,9 +315,18 @@ InitMpGlobalData (
> ASSERT (FALSE);
> }
>
> - for (Index = 0; Index < CpuMpData->CpuCount; ++Index) {
> - StackBase = CpuMpData->Buffer + Index * CpuMpData->CpuApStackSize;
> + //
> + // DXE will reuse stack allocated for APs at PEI phase if it's available.
> + // Let's check it here.
> + //
> + CpuInfoInHob = (CPU_INFO_IN_HOB *)(UINTN)CpuMpData->CpuInfoInHob;
> + if (CpuInfoInHob != NULL && CpuInfoInHob->ApTopOfStack != 0) {
> + StackBase = CpuInfoInHob->ApTopOfStack;
> + } else {
> + StackBase = CpuMpData->Buffer;
> + }
So, if the HOB is not found, then StackBase is set okay.
However, I'm unsure about the other case. The
CPU_INFO_IN_HOB.ApTopOfStack field identifies the *top* of the stack
(highest address, and the stack grows down); however the loop below
*increments* StackBase. Given the incrementing nature of the loop,
shouldn't we first calculate the actual base (= lowest address) from the
CPU_INFO_IN_HOB.ApTopOfStack field?
Actually... I'm even more confused. The CpuMpData->CpuInfoInHob field
points to an *array* of CPU_INFO_IN_HOB structures. Therefore, for any
given processor #N, we should not calculate the stack base as
CpuMpData->CpuInfoInHob->ApTopOfStack + N * CpuMpData->CpuApStackSize
instead we should calculate the stack base as something like:
CpuMpData->CpuInfoInHob[N].ApTopOfStack - CpuMpData->CpuApStackSize
See
- the InitializeApData() function,
- and its call site in the ApWakeupFunction() function.
(To my surprise, I personally modified InitializeApData() earlier, in
commit dd3fa0cd72de ("UefiCpuPkg/MpInitLib: support 64-bit AP stack
addresses", 2016-11-17) -- I've totally forgotten about that by now!)
What do you think?
>
> + for (Index = 0; Index < CpuMpData->CpuCount; ++Index) {
> Status = gDS->GetMemorySpaceDescriptor (StackBase, &MemDesc);
> ASSERT_EFI_ERROR (Status);
>
> @@ -326,6 +336,9 @@ InitMpGlobalData (
> MemDesc.Attributes | EFI_MEMORY_RP
> );
> ASSERT_EFI_ERROR (Status);
> +
> + DEBUG ((DEBUG_VERBOSE, "Stack Guard set at %x [cpu%d]!\n", StackBase,
> Index));
StackBase has type UINTN, and so it should not be printed with %x. It
should be cast to (UINT64), and then printed with %Lx.
Similarly, Index has type UINTN. It should not be printed with %d. It
should be cast to (UINT64) and printed with %Lu.
> + StackBase += CpuMpData->CpuApStackSize;
Again, I don't think the simple increment applies when the
CpuMpData->CpuInfoInHob array exists.
> }
> }
>
>
Thanks,
Laszlo
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