From b801901a9baf65af54fa29dc484c79316269643a Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 7 Feb 2023 00:21:54 +0000 Subject: [PATCH] KVM: SVM: Fix a benign off-by-one bug in AVIC physical table mask commit a2f25d281cbe6bea4e0421beb8b52b5afd46e8e7 upstream. Define the "physical table max index mask" as bits 8:0, not 9:0. x2AVIC currently supports a max of 512 entries, i.e. the max index is 511, and the inputs to GENMASK_ULL() are inclusive. The bug is benign as bit 9 is reserved and never set by KVM, i.e. KVM is just clearing bits that are guaranteed to be zero. Note, as of this writing, APM "Rev. 3.39-October 2022" incorrectly states that bits 11:8 are reserved in Table B-1. VMCB Layout, Control Area. I.e. that table wasn't updated when x2AVIC support was added. Opportunistically fix the comment for the max AVIC ID to align with the code, and clean up comment formatting too. Fixes: eadd6be7bd64 ("KVM: SVM: Introduce logic to (de)activate x2AVIC mode") Cc: stable@vger.kernel.org Cc: Alejandro Jimenez Cc: Suravee Suthikulpanit Signed-off-by: Sean Christopherson Reviewed-by: Suravee Suthikulpanit Tested-by: Suravee Suthikulpanit Message-Id: <20230207002156.521736-2-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/svm.h | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h index 0361626841bc0..236fda748ae96 100644 --- a/arch/x86/include/asm/svm.h +++ b/arch/x86/include/asm/svm.h @@ -256,20 +256,22 @@ enum avic_ipi_failure_cause { AVIC_IPI_FAILURE_INVALID_BACKING_PAGE, }; -#define AVIC_PHYSICAL_MAX_INDEX_MASK GENMASK_ULL(9, 0) +#define AVIC_PHYSICAL_MAX_INDEX_MASK GENMASK_ULL(8, 0) /* - * For AVIC, the max index allowed for physical APIC ID - * table is 0xff (255). + * For AVIC, the max index allowed for physical APIC ID table is 0xfe (254), as + * 0xff is a broadcast to all CPUs, i.e. can't be targeted individually. */ #define AVIC_MAX_PHYSICAL_ID 0XFEULL /* - * For x2AVIC, the max index allowed for physical APIC ID - * table is 0x1ff (511). + * For x2AVIC, the max index allowed for physical APIC ID table is 0x1ff (511). */ #define X2AVIC_MAX_PHYSICAL_ID 0x1FFUL +static_assert((AVIC_MAX_PHYSICAL_ID & AVIC_PHYSICAL_MAX_INDEX_MASK) == AVIC_MAX_PHYSICAL_ID); +static_assert((X2AVIC_MAX_PHYSICAL_ID & AVIC_PHYSICAL_MAX_INDEX_MASK) == X2AVIC_MAX_PHYSICAL_ID); + #define AVIC_HPA_MASK ~((0xFFFULL << 52) | 0xFFF) #define VMCB_AVIC_APIC_BAR_MASK 0xFFFFFFFFFF000ULL -- 2.39.5