[edk2-devel] [PATCH v10 1/4] OvmfPkg: Add memory acceptance event in AmdSevDxe

[Gupta, Pankaj via groups.io]

>>>>> With this patch I observe an issue where my Linux (6.2.0-rc7) guest
>>>>> recur to Bootloader menu again. I am testing this with SEV SNP (w/o
>>>>> UPM). Also, guest don't have lazy memory acceptance support.
>>>>>
>>>>
>>>> Thanks for the report. I'll try to reproduce it on our UEFI and if I'm
>>>> unable, then we'll discuss next steps.
>>>>
>>>
>>> I don't see this in our test Ubuntu 22.04 image from Canonical. Do you
>>
>> Ubuntu 22.04 guest by default run 5.15 kernel? But SEV SNP got
>> merged in 5.19. I don't know currently how we are handling accepting
>> the memory on "ExitBootServices" with or w/o guest supporting SNP.
>>
> 
> It does, but I used the Qemu kernel injection pathway in Ovmf to run a
> build of 6.2.0-rc7. Our testing setup doesn't give the user a boot
> menu to select a kernel, so I wasn't aware that this return to
> bootmenu could happen.
> 
> 
>> This looks to me like it is entering the 'accept' path twice, and so
>> ExitBootServices() is failing twice, resulting in a failed boot.
> 
> The double log is expected behavior because I didn't add a check for
> whether accepting all memory would be a no-op.
> 
> The "Accepting all memory" message occurs twice if the guest does not
> have support for unaccepted memory following this control flow:
> 
> 1. EBS
> 2. [...] Log "Accepting all memory"
> 3. Loop through all memory spaces
> 3a. If the memory space is unaccepted, accept it.
> 3b. Remove the unaccepted memory space.
> 3c. Add a conventional memory space back with the same range and capabilities.
> 4. EBS returns an error since the map key is different.
> 5. OS calls GetMemoryMap to get the updated key.
> 6. OS calls EBS with the updated key.
> 7. [...] Log "Accepting all memory"
> 8. Loop through all memory spaces
> 8a. There are no unaccepted memory spaces left, so nothing happens.

Seems like hitting this all the time. Can't see
EFI_GCD_MEMORY_TYPE_UNACCEPTED memory at all in the memory map.

And always hitting:
if (Desc->GcdMemoryType != EFI_GCD_MEMORY_TYPE_UNACCEPTED) {

So, no memory is getting accepted. Questions below:

- If no memory is getting accepted at all, should guest boot fail with
   below errors?
- Why unaccepted memory not being set in my setup but works fine for
   you? Does it require any other change?

Thanks,
Pankaj

> 9. Return successfully (one would hope)
> 
>> Accepting all memory^M
>> Accepting all memory^M
>> EFI stub: ERROR: exit_boot() failed!^M
>> EFI stub: ERROR: efi_main() failed!^M
> 
> This now does suggest that EBS is failing twice, since after the
> supposed no-op of the second log, the EFI stub's exit_boot claims
> failure. I can't reproduce this part. Would you try adding a log
> within the acceptance loop inside the if that checks for unaccepted
> memory? I'd be curious if the loop is indeed changing the map again,
> despite my claims at idempotency.
> 



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