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KVM: SVM: Drop redundant check in AVIC code on ID during vCPU creation

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Drop avic_get_physical_id_entry()'s compatibility check on the incoming
ID, as its sole caller, avic_init_backing_page(), performs the exact same
check.  Drop avic_get_physical_id_entry() entirely as the only remaining
functionality is getting the address of the Physical ID table, and
accessing the array without an immediate bounds check is kludgy.

Opportunistically add a compile-time assertion to ensure the vcpu_id can't
result in a bounds overflow, e.g. if KVM (really) messed up a maximum
physical ID #define, as well as run-time assertions so that a NULL pointer
dereference is morphed into a safer WARN().

No functional change intended.

Tested-by: Sairaj Kodilkar <sarunkod@amd.com>
Reviewed-by: Naveen N Rao (AMD) <naveen@kernel.org>
Link: https://lore.kernel.org/r/20250611224604.313496-15-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2025-06-11 15:45:16 -07:00
parent 1aa6e256e4
commit c24ed209c4
1 changed files with 15 additions and 22 deletions
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37
arch/x86/kvm/svm/avic.c
View File

@@ -257,26 +257,12 @@ void avic_init_vmcb(struct vcpu_svm *svm, struct vmcb *vmcb)
avic_deactivate_vmcb(svm);
}
static u64 *avic_get_physical_id_entry(struct kvm_vcpu *vcpu,
unsigned int index)
{
u64 *avic_physical_id_table;
struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm);
if ((!x2avic_enabled && index > AVIC_MAX_PHYSICAL_ID) ||
(index > X2AVIC_MAX_PHYSICAL_ID))
return NULL;
avic_physical_id_table = page_address(kvm_svm->avic_physical_id_table_page);
return &avic_physical_id_table[index];
}
static int avic_init_backing_page(struct kvm_vcpu *vcpu)
{
u64 *entry, new_entry;
int id = vcpu->vcpu_id;
struct kvm_svm *kvm_svm = to_kvm_svm(vcpu->kvm);
struct vcpu_svm *svm = to_svm(vcpu);
u32 id = vcpu->vcpu_id;
u64 *table, new_entry;
/*
* Inhibit AVIC if the vCPU ID is bigger than what is supported by AVIC
@@ -292,6 +278,9 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
return 0;
}
BUILD_BUG_ON((AVIC_MAX_PHYSICAL_ID + 1) * sizeof(*table) > PAGE_SIZE ||
(X2AVIC_MAX_PHYSICAL_ID + 1) * sizeof(*table) > PAGE_SIZE);
if (WARN_ON_ONCE(!vcpu->arch.apic->regs))
return -EINVAL;
@@ -310,9 +299,7 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
}
/* Setting AVIC backing page address in the phy APIC ID table */
entry = avic_get_physical_id_entry(vcpu, id);
if (!entry)
return -EINVAL;
table = page_address(kvm_svm->avic_physical_id_table_page);
/* Note, fls64() returns the bit position, +1. */
BUILD_BUG_ON(__PHYSICAL_MASK_SHIFT >
@@ -320,9 +307,9 @@ static int avic_init_backing_page(struct kvm_vcpu *vcpu)
new_entry = avic_get_backing_page_address(svm) |
AVIC_PHYSICAL_ID_ENTRY_VALID_MASK;
WRITE_ONCE(*entry, new_entry);
WRITE_ONCE(table[id], new_entry);
svm->avic_physical_id_cache = entry;
svm->avic_physical_id_cache = &table[id];
return 0;
}
@@ -1005,6 +992,9 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
if (WARN_ON(h_physical_id & ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK))
return;
if (WARN_ON_ONCE(!svm->avic_physical_id_cache))
return;
/*
* No need to update anything if the vCPU is blocking, i.e. if the vCPU
* is being scheduled in after being preempted. The CPU entries in the
@@ -1045,6 +1035,9 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu)
lockdep_assert_preemption_disabled();
if (WARN_ON_ONCE(!svm->avic_physical_id_cache))
return;
/*
* Note, reading the Physical ID entry outside of ir_list_lock is safe
* as only the pCPU that has loaded (or is loading) the vCPU is allowed