Re: [edk2-devel] [PATCH 1/1] OvmfPkg/ResetVector: send post codes to qemu debug console

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

On 1/26/24 14:25, Gerd Hoffmann wrote:
> On Thu, Jan 25, 2024 at 08:47:56PM +0100, Laszlo Ersek wrote:
>> On 1/25/24 08:50, Gerd Hoffmann wrote:
>>> On Wed, Jan 24, 2024 at 05:43:29PM -0800, Erdem Aktas wrote:
>>>> Same for TDX, I did not run it but it should cause failure
>>>> as debugShowPostCode is called OvmfPkg/ResetVector/Ia32/IntelTdx.asm before
>>>> actually the #VE handlers are installed.
>>>>
>>>>> Had a meeting get canceled and so got a chance to test this. As I thought,
>>>>> this causes SEV-ES/SEV-SNP guest failures.
>>>
>>> Hmm, I guess that pretty much kills the idea.  The first post code is
>>> sent before probing for TDX/SEV happens ...
>>
>> Can we salvage it, but make it depend on a minimal source code tweak
>> (ungating)? Changing a single line for debugging (non-TDX / non-SEV-ES
>> guests, anyway) is much easier than coming up with this patch from zero,
>> whenever needed.
>>
>> Can we add "DebugCon.asm" to the tree, plus a *comment* near
>>
>> %include "DebugDisabled.asm"
>>
>> about "DebugCon.asm"?
> 
> Sure, can do that.  I assume the concern about the slowdown is moot if
> this requires an source code patch to be enabled?

Yes, absolutely! Since it's not enabled by default, only for dedicated
debugging sessions, the perf hit (if any) should be fine, IMO.

Laszlo



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