From 5d0316e25defee47c8c7b1b6324244f630b6621f Mon Sep 17 00:00:00 2001 From: Naveen N Rao Date: Fri, 5 Sep 2025 00:03:06 +0530 Subject: [PATCH] x86/cpufeatures: Add X86_FEATURE_X2AVIC_EXT Add CPUID feature bit for x2AVIC extension that enables AMD SVM to support up to 4096 vCPUs in x2AVIC mode. The primary change is in the size of the AVIC Physical ID table, which can now go up to 8 contiguous 4k pages. The number of pages allocated is controlled by the maximum APIC ID for a guest, and that controls the number of pages to allocate for the AVIC Physical ID table. AVIC hardware is enhanced to look up Physical ID table entries for vCPUs > 512 for locating the target APIC backing page and the host APIC ID of the physical core on which the guest vCPU is running. Signed-off-by: Naveen N Rao (AMD) Acked-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/e5c9c471ab99a130bf9b728b77050ab308cf8624.1757009416.git.naveen@kernel.org Signed-off-by: Sean Christopherson --- arch/x86/include/asm/cpufeatures.h | 1 + arch/x86/kernel/cpu/scattered.c | 1 + 2 files changed, 2 insertions(+) diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 6bdf868c8f8ee..7129eb44adadd 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -500,6 +500,7 @@ #define X86_FEATURE_IBPB_EXIT_TO_USER (21*32+14) /* Use IBPB on exit-to-userspace, see VMSCAPE bug */ #define X86_FEATURE_ABMC (21*32+15) /* Assignable Bandwidth Monitoring Counters */ #define X86_FEATURE_MSR_IMM (21*32+16) /* MSR immediate form instructions */ +#define X86_FEATURE_X2AVIC_EXT (21*32+17) /* AMD SVM x2AVIC support for 4k vCPUs */ /* * BUG word(s) diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c index caa4dc885c214..aa7f21f5f46b5 100644 --- a/arch/x86/kernel/cpu/scattered.c +++ b/arch/x86/kernel/cpu/scattered.c @@ -49,6 +49,7 @@ static const struct cpuid_bit cpuid_bits[] = { { X86_FEATURE_PROC_FEEDBACK, CPUID_EDX, 11, 0x80000007, 0 }, { X86_FEATURE_AMD_FAST_CPPC, CPUID_EDX, 15, 0x80000007, 0 }, { X86_FEATURE_MBA, CPUID_EBX, 6, 0x80000008, 0 }, + { X86_FEATURE_X2AVIC_EXT, CPUID_ECX, 6, 0x8000000a, 0 }, { X86_FEATURE_COHERENCY_SFW_NO, CPUID_EBX, 31, 0x8000001f, 0 }, { X86_FEATURE_SMBA, CPUID_EBX, 2, 0x80000020, 0 }, { X86_FEATURE_BMEC, CPUID_EBX, 3, 0x80000020, 0 }, -- 2.47.3