Re: [PATCH v2 3/3] selftest: kvm: Support amx selftest

[Paolo Bonzini <pbonzini@xxxxxxxxxx>]

On 12/22/21 22:47, Yang Zhong wrote:
> +	/* Trigger #NM exception */
> +	__tileloadd(tiledata);
> +	GUEST_SYNC(10);
> +
> +	GUEST_DONE();
> +}
> +
> +void guest_nm_handler(struct ex_regs *regs)
> +{
> +	/* Check if #NM is triggered by XFEATURE_MASK_XTILEDATA */
> +	GUEST_SYNC(7);
> +	GUEST_ASSERT(rdmsr(MSR_IA32_XFD_ERR) == XFEATURE_MASK_XTILEDATA);
> +	GUEST_SYNC(8);
> +	GUEST_ASSERT(rdmsr(MSR_IA32_XFD_ERR) == XFEATURE_MASK_XTILEDATA);
> +	/* Clear xfd_err */
> +	wrmsr(MSR_IA32_XFD_ERR, 0);
> +	regs->rip += 3;
> +	GUEST_SYNC(9);
> +}

I don't understand why "regs->rip += 3" is needed though.

My idea was that, after GUEST_SYNC(9) and IRET, the guest would execute 
__tileloadd again; this time without generating #NM, so that after 
GUEST_SYNC(10) the host sees the loaded data in TMM0.

Thanks,

Paolo