From: Saurabh Sengar ssengar@linux.microsoft.com
[ 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.mi... 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 --- arch/x86/hyperv/hv_vtl.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/x86/hyperv/hv_vtl.c b/arch/x86/hyperv/hv_vtl.c index 96e6c51515f50..cf1b78cb2d043 100644 --- a/arch/x86/hyperv/hv_vtl.c +++ b/arch/x86/hyperv/hv_vtl.c @@ -16,6 +16,11 @@ extern struct boot_params boot_params; static struct real_mode_header hv_vtl_real_mode_header;
+static bool __init hv_vtl_msi_ext_dest_id(void) +{ + return true; +} + void __init hv_vtl_init_platform(void) { pr_info("Linux runs in Hyper-V Virtual Trust Level\n"); @@ -38,6 +43,8 @@ void __init hv_vtl_init_platform(void) x86_platform.legacy.warm_reset = 0; x86_platform.legacy.reserve_bios_regions = 0; x86_platform.legacy.devices.pnpbios = 0; + + x86_init.hyper.msi_ext_dest_id = hv_vtl_msi_ext_dest_id; }
static inline u64 hv_vtl_system_desc_base(struct ldttss_desc *desc)