Re: [PATCH v10 10/11] x86/tdx: Don't write CSTAR MSR on Intel

[Thomas Gleixner]

On Thu, Oct 14 2021 at 06:47, Andi Kleen wrote:

>>> -	wrmsrl(MSR_CSTAR, (unsigned long)entry_SYSCALL_compat);
>>> +	/*
>>> +	 * CSTAR is not needed on Intel because it doesn't support
>>> +	 * 32bit SYSCALL, but only SYSENTER. On a TDX guest
>>> +	 * it leads to a #GP.
>> Sigh. Above you write it raises #VE, but now it's #GP !?!
>
>
> The unhandled #VE trap is handled like a #GP, which is then caught by 
> the kernel wrmsr code.

That's completely irrelevant because that's an implementation detail of
the #VE handler. It raises #VE in the first place and that's unwanted no
matter what the #VE handler does with it. It could just pretent that
it's fine and move on.

Thanks,

        tglx