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KVM: x86/hyperv: Check for NULL vCPU Hyper-V object in kvm_hv_get_tlb_flush_fifo()

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Check for a NULL Hyper-V object in kvm_hv_get_tlb_flush_fifo() instead of
relying on the caller to do so.  This will allow fixing a cross-vCPU race
where KVM can access a vCPU's FIFO before it's fully initialized, without
having to jump through too many cognitive hoops to reason about the
correctness of the logic.

Ignoring changes in ordering that only affect the aforementioned race, no
functional change intended.

Reviewed-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com>
Link: https://patch.msgid.link/20260630225619.511632-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-06-30 15:56:09 -07:00
parent d151ca6e12
commit b6de8bfdab
2 changed files with 11 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
arch/x86/kvm/hyperv.c
View File

@ -1939,13 +1939,11 @@ static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu, u64 *entries, int count,
bool is_guest_mode)
{
struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
u64 flush_all_entry = KVM_HV_TLB_FLUSHALL_ENTRY;
if (!hv_vcpu)
return;
tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(vcpu, is_guest_mode);
if (!tlb_flush_fifo)
return;
spin_lock(&tlb_flush_fifo->write_lock);
@ -1972,15 +1970,16 @@ static void hv_tlb_flush_enqueue(struct kvm_vcpu *vcpu, u64 *entries, int count,
int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
{
struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
u64 entries[KVM_HV_TLB_FLUSH_FIFO_SIZE];
int i, j, count;
gva_t gva;
if (!tdp_enabled || !hv_vcpu)
if (!tdp_enabled)
return -EINVAL;
tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(vcpu, is_guest_mode(vcpu));
if (!tlb_flush_fifo)
return -EINVAL;
count = kfifo_out(&tlb_flush_fifo->entries, entries, KVM_HV_TLB_FLUSH_FIFO_SIZE);

7
arch/x86/kvm/hyperv.h
View File

@ -202,6 +202,9 @@ static inline struct kvm_vcpu_hv_tlb_flush_fifo *kvm_hv_get_tlb_flush_fifo(struc
int i = is_guest_mode ? HV_L2_TLB_FLUSH_FIFO :
HV_L1_TLB_FLUSH_FIFO;
if (!hv_vcpu)
return NULL;
return &hv_vcpu->tlb_flush_fifo[i];
}
@ -209,10 +212,12 @@ static inline void kvm_hv_vcpu_purge_flush_tlb(struct kvm_vcpu *vcpu)
{
struct kvm_vcpu_hv_tlb_flush_fifo *tlb_flush_fifo;
if (!to_hv_vcpu(vcpu) || !kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu))
if (!kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu))
return;
tlb_flush_fifo = kvm_hv_get_tlb_flush_fifo(vcpu, is_guest_mode(vcpu));
if (!tlb_flush_fifo)
return;
kfifo_reset_out(&tlb_flush_fifo->entries);
}