Re: [PATCH v2] x86/hyperv: Allow 15-bit APIC IDs for VTL platforms

[Wei Liu]

On Tue, Jan 16, 2024 at 03:25:47PM +0000, Michael Kelley wrote:
> From: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx> Sent: Monday, January 15, 2024 9:58 AM
> > 
> > The current method for signaling the compatibility of a Hyper-V host
> > with MSIs featuring 15-bit APIC IDs relies on a synthetic cpuid leaf.
> > However, for higher VTLs, this leaf is not reported, due to the absence
> > of an IO-APIC.
> > 
> > As an alternative, assume that when running at a high VTL, the host
> > supports 15-bit APIC IDs. This assumption is safe, as Hyper-V does not
> > employ any architectural MSIs at higher VTLs
> > 
> > This unblocks startup of VTL2 environments with more than 256 CPUs.
> > 
> > Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>
[...]
> 
> Reviewed-by: Michael Kelley <mhklinux@xxxxxxxxxxx>

Applied. Thanks.