linux-kernel - [PATCH 4.19 14/37] KVM: x86: get smi pending status correctly

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Date:   Tue,  2 Feb 2021 14:38:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jay Zhou <jianjay.zhou@...wei.com>,
        Shengen Zhuang <zhuangshengen@...wei.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.19 14/37] KVM: x86: get smi pending status correctly

From: Jay Zhou <jianjay.zhou@...wei.com>

commit 1f7becf1b7e21794fc9d460765fe09679bc9b9e0 upstream.

The injection process of smi has two steps:

    Qemu                        KVM
Step1:
    cpu->interrupt_request &= \
        ~CPU_INTERRUPT_SMI;
    kvm_vcpu_ioctl(cpu, KVM_SMI)

                                call kvm_vcpu_ioctl_smi() and
                                kvm_make_request(KVM_REQ_SMI, vcpu);

Step2:
    kvm_vcpu_ioctl(cpu, KVM_RUN, 0)

                                call process_smi() if
                                kvm_check_request(KVM_REQ_SMI, vcpu) is
                                true, mark vcpu->arch.smi_pending = true;

The vcpu->arch.smi_pending will be set true in step2, unfortunately if
vcpu paused between step1 and step2, the kvm_run->immediate_exit will be
set and vcpu has to exit to Qemu immediately during step2 before mark
vcpu->arch.smi_pending true.
During VM migration, Qemu will get the smi pending status from KVM using
KVM_GET_VCPU_EVENTS ioctl at the downtime, then the smi pending status
will be lost.

Signed-off-by: Jay Zhou <jianjay.zhou@...wei.com>
Signed-off-by: Shengen Zhuang <zhuangshengen@...wei.com>
Message-Id: <20210118084720.1585-1-jianjay.zhou@...wei.com>
Cc: stable@...r.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/x86.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -102,6 +102,7 @@ static u64 __read_mostly cr4_reserved_bi
 
 static void update_cr8_intercept(struct kvm_vcpu *vcpu);
 static void process_nmi(struct kvm_vcpu *vcpu);
+static void process_smi(struct kvm_vcpu *vcpu);
 static void enter_smm(struct kvm_vcpu *vcpu);
 static void __kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags);
 static void store_regs(struct kvm_vcpu *vcpu);
@@ -3499,6 +3500,10 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_
 					       struct kvm_vcpu_events *events)
 {
 	process_nmi(vcpu);
+
+	if (kvm_check_request(KVM_REQ_SMI, vcpu))
+		process_smi(vcpu);
+
 	/*
 	 * FIXME: pass injected and pending separately.  This is only
 	 * needed for nested virtualization, whose state cannot be