On Thu, Aug 22, 2024 at 03:22:35PM +0800, Tao Su wrote:
> On Tue, Aug 20, 2024 at 04:04:31PM -0700, Keith Busch wrote:
> > + if (map == 1 && !v)
> > + return avx_0f_table[ctxt->b];
> > + return (struct opcode){.flags = NotImpl};
>
> Can we check whether the host supports AVX? I.e. if the host does not support
> AVX, set NotImpl. I am thinking that if the host does not support AVX, perhaps
> the guest executing AVX instructions will cause the host to panic, because the
> host will execute AVX instructions during the simulation.
>
> Yeah if the host does not support AVX, it may not report AVX to the guest, but
> the guest can always ignore the AVX check, such as the code in the commit.
That's a good thought. Here is how I rationalized not adding additional
checks for it:
If the guest cpu doesn't support AVX, I think it should fail then and
there rather than trap to the hypervisor running on the host, so this
new code wouldn't get a chance to attempt emulating it.
In the case where the host doesn't support AVX, but the guest does
support it, then I assume the VM is running on an emulated CPU and not
using kvm acceleration anymore.
Anyway, I haven't tried it, so not entirely confident that's how this
all works. I was mainly following the existing SSE emulations, which
don't have CPU support checks either. I don't think it's a problem to
add such checks though, so happy to do it if needed.
