Saurabh Sengar 2984f26a46 x86/hyperv: Allow 15-bit APIC IDs for VTL platforms
[ Upstream commit 0d63e4c0ebc2b5c329babde44fd61d3f08db814d ]

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@linux.microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/1705341460-18394-1-git-send-email-ssengar@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <1705341460-18394-1-git-send-email-ssengar@linux.microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-03-26 18:19:15 -04:00
..
2023-08-31 12:20:12 -07:00
2023-09-05 10:15:22 -07:00
2023-09-05 10:09:31 -07:00
2024-02-16 19:10:52 +01:00
2024-02-23 09:25:03 +01:00