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

[Andi Kleen]

> > -	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.

So both are correct.

>          Intel CPUs do not support 32-bit SYSCALL. Writing to MSR_CSTAR
>          is normaly ignored by the CPU, but raises a #VE trap in a TDX
>          guest.
>
> Hmm?