From: Vitaly Kuznetsov vkuznets@redhat.com
stable inclusion from stable-v5.10.85 commit 06368922f38f5a7a41a097c048f714e265492193 bugzilla: 186032 https://gitee.com/openeuler/kernel/issues/I4QVI4
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit 1ebfaa11ebb5b603a3c3f54b2e84fcf1030f5a14 upstream.
Prior to commit 0baedd792713 ("KVM: x86: make Hyper-V PV TLB flush use tlb_flush_guest()"), kvm_hv_flush_tlb() was using 'KVM_REQ_TLB_FLUSH | KVM_REQUEST_NO_WAKEUP' when making a request to flush TLBs on other vCPUs and KVM_REQ_TLB_FLUSH is/was defined as:
(0 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
so KVM_REQUEST_WAIT was lost. Hyper-V TLFS, however, requires that "This call guarantees that by the time control returns back to the caller, the observable effects of all flushes on the specified virtual processors have occurred." and without KVM_REQUEST_WAIT there's a small chance that the vCPU making the TLB flush will resume running before all IPIs get delivered to other vCPUs and a stale mapping can get read there.
Fix the issue by adding KVM_REQUEST_WAIT flag to KVM_REQ_TLB_FLUSH_GUEST: kvm_hv_flush_tlb() is the sole caller which uses it for kvm_make_all_cpus_request()/kvm_make_vcpus_request_mask() where KVM_REQUEST_WAIT makes a difference.
Cc: stable@kernel.org Fixes: 0baedd792713 ("KVM: x86: make Hyper-V PV TLB flush use tlb_flush_guest()") Signed-off-by: Vitaly Kuznetsov vkuznets@redhat.com Message-Id: 20211209102937.584397-1-vkuznets@redhat.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Chen Jun chenjun102@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- arch/x86/include/asm/kvm_host.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index dd2966759301..fcb5f0090a5f 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -85,7 +85,7 @@ KVM_ARCH_REQ_FLAGS(25, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) #define KVM_REQ_TLB_FLUSH_CURRENT KVM_ARCH_REQ(26) #define KVM_REQ_TLB_FLUSH_GUEST \ - KVM_ARCH_REQ_FLAGS(27, KVM_REQUEST_NO_WAKEUP) + KVM_ARCH_REQ_FLAGS(27, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) #define KVM_REQ_APF_READY KVM_ARCH_REQ(28) #define KVM_REQ_MSR_FILTER_CHANGED KVM_ARCH_REQ(29)