Re: [PATCH v13 45/46] UefiCpuPkg/MpInitLib: Prepare SEV-ES guest APs for OS use

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

On 07/31/20 23:38, Laszlo Ersek wrote:
> On 07/31/20 16:47, Tom Lendacky wrote:
>> On 7/31/20 9:44 AM, Tom Lendacky wrote:
>>> On 7/31/20 8:36 AM, Tom Lendacky wrote:
>>>> On 7/31/20 7:43 AM, Laszlo Ersek wrote:
>>>>> Hi Tom,
>>>>
>>>> Hi Laszlo,
>>>
>>> Hi Laszlo,
>>>
>>> Can you try this incremental patch to see if it fixes the issue you're
>>> seeing? If it does, I'll merge it into patch #45 and send out a v14.
>>
>> Looking at the formatting, I'm not sure if Thunderbird messed up the
>> diff. I'll send you another copy directly to you using git send-email
>> just in case.
> 
> I got the separate copy; I'll report back sometime next week.

The update works fine; IA32 OVMF boots OK with it.

I agree with squashing the update into patch #45, but before sending
v14, maybe we should get some feedback for the MdeModulePkg patches too,
at long last. :/

Thanks!
Laszlo


> 
>>> diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
>>> b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
>>> index 7165bcf3124a..2c00d72ddefe 100644
>>> --- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
>>> +++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
>>> @@ -365,9 +365,9 @@ RelocateApLoop (
>>>       MwaitSupport,
>>>
>>>       CpuMpData->ApTargetCState,
>>>
>>>       CpuMpData->PmCodeSegment,
>>>
>>> -    CpuMpData->Pm16CodeSegment,
>>>
>>>       StackStart - ProcessorNumber * AP_SAFE_STACK_SIZE,
>>>
>>>       (UINTN) &mNumberToFinish,
>>>
>>> +    CpuMpData->Pm16CodeSegment,
>>>
>>>       CpuMpData->SevEsAPBuffer,
>>>
>>>       CpuMpData->WakeupBuffer
>>>
>>>       );
>>>
>>> diff --git a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
>>> b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
>>> index 309d53bf3b37..7e81d24aa60f 100644
>>> --- a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
>>> +++ b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
>>> @@ -226,7 +226,10 @@ SwitchToRealProcStart:
>>>   SwitchToRealProcEnd:
>>>
>>>  
>>>  
>>> ;-------------------------------------------------------------------------------------
>>>
>>>
>>> -;  AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment,
>>> TopOfApStack, CountTofinish);
>>>
>>> +;  AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment,
>>> TopOfApStack, CountTofinish, Pm16CodeSegment, SevEsAPJumpTable,
>>> WakeupBuffer);
>>>
>>> +;
>>>
>>> +;  The last three parameters (Pm16CodeSegment, SevEsAPJumpTable and
>>> WakeupBuffer) are
>>>
>>> +;  specific to SEV-ES support and are not applicable on IA32.
>>>
>>>  
>>> ;-------------------------------------------------------------------------------------
>>>
>>>
>>>   global ASM_PFX(AsmRelocateApLoop)
>>>
>>>   ASM_PFX(AsmRelocateApLoop):
>>>
>>> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h
>>> b/UefiCpuPkg/Library/MpInitLib/MpLib.h
>>> index 267aa5201c50..02652eaae126 100644
>>> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.h
>>> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h
>>> @@ -350,9 +350,9 @@ VOID
>>>     IN BOOLEAN                 MwaitSupport,
>>>
>>>     IN UINTN                   ApTargetCState,
>>>
>>>     IN UINTN                   PmCodeSegment,
>>>
>>> -  IN UINTN                   Pm16CodeSegment,
>>>
>>>     IN UINTN                   TopOfApStack,
>>>
>>>     IN UINTN                   NumberToFinish,
>>>
>>> +  IN UINTN                   Pm16CodeSegment,
>>>
>>>     IN UINTN                   SevEsAPJumpTable,
>>>
>>>     IN UINTN                   WakeupBuffer
>>>
>>>     );
>>>
>>> diff --git a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
>>> b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
>>> index 3b8ec477b8b3..5d30f35b201c 100644
>>> --- a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
>>> +++ b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
>>> @@ -491,13 +491,13 @@ PM16Mode:
>>>   SwitchToRealProcEnd:
>>>
>>>  
>>>  
>>> ;-------------------------------------------------------------------------------------
>>>
>>>
>>> -;  AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment,
>>> Pm16CodeSegment, TopOfApStack, CountTofinish, SevEsAPJumpTable,
>>> WakeupBuffer);
>>>
>>> +;  AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment,
>>> TopOfApStack, CountTofinish, Pm16CodeSegment, SevEsAPJumpTable,
>>> WakeupBuffer);
>>>
>>>  
>>> ;-------------------------------------------------------------------------------------
>>>
>>>
>>>   global ASM_PFX(AsmRelocateApLoop)
>>>
>>>   ASM_PFX(AsmRelocateApLoop):
>>>
>>>   AsmRelocateApLoopStart:
>>>
>>>   BITS 64
>>>
>>> -    cmp        qword [rsp + 56], 0
>>>
>>> +    cmp        qword [rsp + 56], 0  ; SevEsAPJumpTable
>>>
>>>       je         NoSevEs
>>>
>>>  
>>>       ;
>>>
>>> @@ -539,16 +539,17 @@ BITS 64
>>>  
>>>   NoSevEs:
>>>
>>>       cli                          ; Disable interrupt before
>>> switching to 32-bit mode
>>>
>>> -    mov        rax, [rsp + 48]   ; CountTofinish
>>>
>>> +    mov        rax, [rsp + 40]   ; CountTofinish
>>>
>>>       lock dec   dword [rax]       ; (*CountTofinish)--
>>>
>>>  
>>> +    mov        r10, [rsp + 48]   ; Pm16CodeSegment
>>>
>>>       mov        rax, [rsp + 56]   ; SevEsAPJumpTable
>>>
>>>       mov        rbx, [rsp + 64]   ; WakeupBuffer
>>>
>>> -    mov        rsp, [rsp + 40]   ; TopOfApStack
>>>
>>> +    mov        rsp, r9           ; TopOfApStack
>>>
>>>  
>>>       push       rax               ; Save SevEsAPJumpTable
>>>
>>>       push       rbx               ; Save WakeupBuffer
>>>
>>> -    push       r9                ; Save Pm16CodeSegment
>>>
>>> +    push       r10               ; Save Pm16CodeSegment
>>>
>>>       push       rcx               ; Save MwaitSupport
>>>
>>>       push       rdx               ; Save ApTargetCState
>>>
>>>  
>>>
>>>
>>>>
>>>>>
>>>>> On 07/30/20 20:43, Tom Lendacky wrote:
>>>>>> From: Tom Lendacky <thomas.lendacky@amd.com>
>>>>>>
>>>>>> BZ:
>>>>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.tianocore.org%2Fshow_bug.cgi%3Fid%3D2198&amp;data=02%7C01%7Cthomas.lendacky%40amd.com%7Cb8c77cf296c949d2bbd808d8354f542b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637317962138028351&amp;sdata=HISHZmLjOc%2FfgVrBm8MlNeDAk453NJ64%2B51bETZj4rk%3D&amp;reserved=0
>>>>>>
>>>>>>
>>>>>>
>>>>>> Before UEFI transfers control to the OS, it must park the AP. This is
>>>>>> done using the AsmRelocateApLoop function to transition into 32-bit
>>>>>> non-paging mode. For an SEV-ES guest, a few additional things must be
>>>>>> done:
>>>>>>     - AsmRelocateApLoop must be updated to support SEV-ES. This means
>>>>>>       performing a VMGEXIT AP Reset Hold instead of an MWAIT or HLT
>>>>>> loop.
>>>>>>     - Since the AP must transition to real mode, a small routine is
>>>>>> copied
>>>>>>       to the WakeupBuffer area. Since the WakeupBuffer will be used by
>>>>>>       the AP during OS booting, it must be placed in reserved memory.
>>>>>>       Additionally, the AP stack must be located where it can be
>>>>>> accessed
>>>>>>       in real mode.
>>>>>>     - Once the AP is in real mode it will transfer control to the
>>>>>>       destination specified by the OS in the SEV-ES AP Jump Table. The
>>>>>>       SEV-ES AP Jump Table address is saved by the hypervisor for
>>>>>> the OS
>>>>>>       using the GHCB VMGEXIT AP Jump Table exit code.
>>>>>>
>>>>>> Cc: Eric Dong <eric.dong@intel.com>
>>>>>> Cc: Ray Ni <ray.ni@intel.com>
>>>>>> Cc: Laszlo Ersek <lersek@redhat.com>
>>>>>> Reviewed-by: Eric Dong <eric.dong@intel.com>
>>>>>> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
>>>>>> ---
>>>>>>    UefiCpuPkg/Library/MpInitLib/MpLib.h          |   8 +-
>>>>>>    UefiCpuPkg/Library/MpInitLib/DxeMpLib.c       |  54 +++++++-
>>>>>>    UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm | 131
>>>>>> ++++++++++++++++--
>>>>>>    3 files changed, 175 insertions(+), 18 deletions(-)
>>>>>
>>>>> Now that this series is almost ready to merge, I've done a bit of
>>>>> regression-testing.
>>>>>
>>>>> Unfortunately, this patch breaks booting with IA32 OVMF.
>>>>>
>>>>> More precisely, it breaks the IA32 version of DxeMpInitLib.
>>>>
>>>> Yeah, that's not good.  I will look into this based on your input below.
>>>> What's strange is that my system doesn't hang and successfully boots all
>>>> APs (up to 64 is what I've tested with).
>>>>
>>>> But, yes, both call sites should be the same and I will make that
>>>> change.
>>>>
>>>>>
>>>>> The symptom is that just when the OS would be launched, the
>>>>> multiprocessor guest hangs. This is how the log terminates:
>>>>>
>>>>>> FSOpen: Open
>>>>>> '\370ac550dcaa48b88f1ca75ad903b0e7\4.16.7-100.fc26.i686\linux'
>>>>>> Success
>>>>>> [Security] 3rd party image[0] can be loaded after EndOfDxe:
>>>>>> PciRoot(0x0)/Pci(0x2,0x1)/Pci(0x0,0x0)/Scsi(0x0,0x0)/HD(1,GPT,D9F1FBA5-E5D3-440A-B6A7-87B593E4FAB1,0x800,0x100000)/\370ac550dcaa48b88f1ca75ad903b0e7\4.16.7-100.fc26.i686\linux.
>>>>>>
>>>>>>
>>>>>> InstallProtocolInterface: [EfiLoadedImageProtocol] 853A03A8
>>>>>> Loading driver at 0x00083E72000 EntryPoint=0x00083E76680
>>>>>> InstallProtocolInterface: [EfiLoadedImageDevicePathProtocol] 853A0510
>>>>>> ProtectUefiImageCommon - 0x853A03A8
>>>>>>     - 0x0000000083E72000 - 0x0000000000E75000
>>>>>> FSOpen: Open
>>>>>> '370ac550dcaa48b88f1ca75ad903b0e7\4.16.7-100.fc26.i686\initrd'
>>>>>> Success
>>>>>> PixelBlueGreenRedReserved8BitPerColor
>>>>>> ConvertPages: range 400000 - 1274FFF covers multiple entries
>>>>>> SmmInstallProtocolInterface: [EdkiiSmmExitBootServicesProtocol] 0
>>>>>> CpuDxe: 5-Level Paging = 0
>>>>>> [HANG]
>>>>>
>>>>> Meanwhile some guest CPUs are pegged.
>>>>>
>>>>> Normally, when this series is not applied, the next log entry is (in
>>>>> place of [HANG]):
>>>>>
>>>>>> MpInitChangeApLoopCallback() done!
>>>>>
>>>>> I've identified this patch by bisection, after applying the series on
>>>>> current master (137c2c6eff67, "Revert "BaseTools/PatchCheck.py: Add
>>>>> LicenseCheck"", 2020-07-31).
>>>>>
>>>>> Here's the bisection log:
>>>>>
>>>>>> git bisect start
>>>>>> # good: [137c2c6eff67f4750d77e8e40af6683c412d3ed0] Revert
>>>>>> "BaseTools/PatchCheck.py: Add LicenseCheck"
>>>>>> git bisect good 137c2c6eff67f4750d77e8e40af6683c412d3ed0
>>>>>> # bad: [d3f7971f4f70c9f39170b42af837e58e59435ad3] Maintainers.txt: Add
>>>>>> reviewers for the OvmfPkg SEV-related files
>>>>>> git bisect bad d3f7971f4f70c9f39170b42af837e58e59435ad3
>>>>>> # good: [9551e3fc61ba0c0ddf8e79b425a22aa7dd61cb8b] OvmfPkg/VmgExitLib:
>>>>>> Add support for RDTSCP NAE events
>>>>>> git bisect good 9551e3fc61ba0c0ddf8e79b425a22aa7dd61cb8b
>>>>>> # good: [10acf16b38522d8a1b538b3aa432daaa72c0e97b] OvmfPkg: Reserve a
>>>>>> page in memory for the SEV-ES usage
>>>>>> git bisect good 10acf16b38522d8a1b538b3aa432daaa72c0e97b
>>>>>> # good: [ccb4267e76b6474657c41bef7e76a980930c22ea] UefiCpuPkg: Add a
>>>>>> 16-bit protected mode code segment descriptor
>>>>>> git bisect good ccb4267e76b6474657c41bef7e76a980930c22ea
>>>>>> # good: [94e238ae37505cfb081f3b9b4632067e4a113cf9] OvmfPkg: Use the
>>>>>> SEV-ES work area for the SEV-ES AP reset vector
>>>>>> git bisect good 94e238ae37505cfb081f3b9b4632067e4a113cf9
>>>>>> # bad: [16c21b9d10b032d66d4105dd4693fd9dc6e6ec18]
>>>>>> UefiCpuPkg/MpInitLib:
>>>>>> Prepare SEV-ES guest APs for OS use
>>>>>> git bisect bad 16c21b9d10b032d66d4105dd4693fd9dc6e6ec18
>>>>>> # good: [49855596e383ab2aa6410fa060e22d4817d8e64e] OvmfPkg: Move the
>>>>>> GHCB allocations into reserved memory
>>>>>> git bisect good 49855596e383ab2aa6410fa060e22d4817d8e64e
>>>>>> # first bad commit: [16c21b9d10b032d66d4105dd4693fd9dc6e6ec18]
>>>>>> UefiCpuPkg/MpInitLib: Prepare SEV-ES guest APs for OS use
>>>>>
>>>>> So clearly we should be looking for an IA32-specific change, or
>>>>> IA32-specific *omission*, in this patch, that could cause the problem.
>>>>>
>>>>> The bug is the following:
>>>>>
>>>>> On 07/30/20 20:43, Tom Lendacky wrote:
>>>>>>
>>>>>> diff --git a/UefiCpuPkg/Library/MpInitLib/MpLib.h
>>>>>> b/UefiCpuPkg/Library/MpInitLib/MpLib.h
>>>>>> index b1a9d99cb3eb..267aa5201c50 100644
>>>>>> --- a/UefiCpuPkg/Library/MpInitLib/MpLib.h
>>>>>> +++ b/UefiCpuPkg/Library/MpInitLib/MpLib.h
>>>>>> @@ -349,8 +350,11 @@ VOID
>>>>>>      IN BOOLEAN                 MwaitSupport,
>>>>>>      IN UINTN                   ApTargetCState,
>>>>>>      IN UINTN                   PmCodeSegment,
>>>>>> +  IN UINTN                   Pm16CodeSegment,
>>>>>>      IN UINTN                   TopOfApStack,
>>>>>> -  IN UINTN                   NumberToFinish
>>>>>> +  IN UINTN                   NumberToFinish,
>>>>>> +  IN UINTN                   SevEsAPJumpTable,
>>>>>> +  IN UINTN                   WakeupBuffer
>>>>>>      );
>>>>>>
>>>>>>    /**
>>>>>
>>>>> (1) This hunk modifies the parameter list of functions pointed-to by
>>>>> ASM_RELOCATE_AP_LOOP.
>>>>>
>>>>>> diff --git a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
>>>>>> b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
>>>>>> index 9115ff9e3e30..7165bcf3124a 100644
>>>>>> --- a/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
>>>>>> +++ b/UefiCpuPkg/Library/MpInitLib/DxeMpLib.c
>>>>>> @@ -330,17 +350,26 @@ RelocateApLoop (
>>>>>>      BOOLEAN                MwaitSupport;
>>>>>>      ASM_RELOCATE_AP_LOOP   AsmRelocateApLoopFunc;
>>>>>>      UINTN                  ProcessorNumber;
>>>>>> +  UINTN                  StackStart;
>>>>>>
>>>>>>      MpInitLibWhoAmI (&ProcessorNumber);
>>>>>>      CpuMpData    = GetCpuMpData ();
>>>>>>      MwaitSupport = IsMwaitSupport ();
>>>>>> +  if (CpuMpData->SevEsIsEnabled) {
>>>>>> +    StackStart = CpuMpData->SevEsAPResetStackStart;
>>>>>> +  } else {
>>>>>> +    StackStart = mReservedTopOfApStack;
>>>>>> +  }
>>>>>>      AsmRelocateApLoopFunc = (ASM_RELOCATE_AP_LOOP) (UINTN)
>>>>>> mReservedApLoopFunc;
>>>>>>      AsmRelocateApLoopFunc (
>>>>>>        MwaitSupport,
>>>>>>        CpuMpData->ApTargetCState,
>>>>>>        CpuMpData->PmCodeSegment,
>>>>>> -    mReservedTopOfApStack - ProcessorNumber * AP_SAFE_STACK_SIZE,
>>>>>> -    (UINTN) &mNumberToFinish
>>>>>> +    CpuMpData->Pm16CodeSegment,
>>>>>> +    StackStart - ProcessorNumber * AP_SAFE_STACK_SIZE,
>>>>>> +    (UINTN) &mNumberToFinish,
>>>>>> +    CpuMpData->SevEsAPBuffer,
>>>>>> +    CpuMpData->WakeupBuffer
>>>>>>        );
>>>>>>      //
>>>>>>      // It should never reach here
>>>>>
>>>>> (2) This hunk modifies the call site, in accordance with the prototype
>>>>> change at (1).
>>>>>
>>>>>> diff --git a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
>>>>>> b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
>>>>>> index 6956b408d004..3b8ec477b8b3 100644
>>>>>> --- a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
>>>>>> +++ b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
>>>>>> @@ -465,6 +465,10 @@ BITS 16
>>>>>
>>>>>>        ;     - IP for Real Mode (two bytes)
>>>>>>        ;     - CS for Real Mode (two bytes)
>>>>>>        ;
>>>>>> +    ; This label is also used with AsmRelocateApLoop. During MP
>>>>>> finalization,
>>>>>> +    ; the code from PM16Mode to SwitchToRealProcEnd is copied to the
>>>>>> start of
>>>>>> +    ; the WakeupBuffer, allowing a parked AP to be booted by an OS.
>>>>>> +    ;
>>>>>>    PM16Mode:
>>>>>>        mov        eax, cr0                    ; Read CR0
>>>>>>        btr        eax, 0                      ; Set PE=0
>>>>>> @@ -487,32 +491,95 @@ PM16Mode:
>>>>>>    SwitchToRealProcEnd:
>>>>>>
>>>>>>   
>>>>>> ;-------------------------------------------------------------------------------------
>>>>>>
>>>>>>
>>>>>> -;  AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment,
>>>>>> TopOfApStack, CountTofinish);
>>>>>> +;  AsmRelocateApLoop (MwaitSupport, ApTargetCState, PmCodeSegment,
>>>>>> Pm16CodeSegment, TopOfApStack, CountTofinish, SevEsAPJumpTable,
>>>>>> WakeupBuffer);
>>>>>>   
>>>>>> ;-------------------------------------------------------------------------------------
>>>>>>
>>>>>>
>>>>>>    global ASM_PFX(AsmRelocateApLoop)
>>>>>>    ASM_PFX(AsmRelocateApLoop):
>>>>>>    AsmRelocateApLoopStart:
>>>>>>    BITS 64
>>>>>
>>>>> (3) Unfortunately, the patch only adapts the X64 implementation of the
>>>>> AsmRelocateApLoopStart() function to the new prototype; the IA32
>>>>> implementation no longer matches the call site.
>>>>>
>>>>> (I'm not sure if the intent was for the IA32 version to simply ignore
>>>>> the new parameters, but even in that case, the "Pm16CodeSegment"
>>>>> parameter is inserted in the middle of the parameter list, likely
>>>>> offsetting the rest.)
>>>>>
>>>>> The problem is foreshadowed even by hunk (2). Namely, in hunk (2), the
>>>>>
>>>>>     s/mReservedTopOfApStack/StackStart/
>>>>>
>>>>> replacement is *more difficult* to verify than necessary -- exactly
>>>>> because "CpuMpData->Pm16CodeSegment" is inserted *before* it.
>>>>
>>>> I can do one of two things here and just put the 3 new parameters at the
>>>> end of the function call rather than keeping the code segment parameters
>>>> together or update the IA32 call site. Let me see which looks best. But
>>>> I'll likely update the IA32 call site no matter what with at least
>>>> comments about the parameters that aren't used, either way.
>>>>
>>>> Thanks,
>>>> Tom
>>>>
>>>>>
>>>>> Thanks
>>>>> Laszlo
>>>>>
>>
>