linux-kernel - [PATCH 4/9] KVM: x86: Invoke kvm_smm_changed() immediately after clearing SMM flag

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Message-Id: <20210609185619.992058-5-seanjc@google.com>
Date:   Wed,  9 Jun 2021 11:56:14 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        syzbot+fb0b6a7e8713aeb0319c@...kaller.appspotmail.com
Subject: [PATCH 4/9] KVM: x86: Invoke kvm_smm_changed() immediately after
 clearing SMM flag

Move RSM emulation's call to kvm_smm_changed() from .post_leave_smm() to
.exiting_smm(), leaving behind the MMU context reset.  The primary
motivation is to allow for future cleanup, but this also fixes a bug of
sorts by queueing KVM_REQ_EVENT even if RSM causes shutdown, e.g. to let
an INIT wake the vCPU from shutdown.  Of course, KVM doesn't properly
emulate a shutdown state, e.g. KVM doesn't block SMIs after shutdown, and
immediately exits to userspace, so the event request is a moot point in
practice.

Moving kvm_smm_changed() also moves the RSM tracepoint.  This isn't
strictly necessary, but will allow consolidating the SMI and RSM
tracepoints in a future commit (by also moving the SMI tracepoint).
Invoking the tracepoint before loading SMRAM state also means the SMBASE
that reported in the tracepoint will point that the state that will be
used for RSM, as opposed to the SMBASE _after_ RSM completes, which is
arguably a good thing if the tracepoint is being used to debug a RSM/SMM
issue.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/x86.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 69a71c5019c1..76ba28865824 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7109,7 +7109,7 @@ static void emulator_exiting_smm(struct x86_emulate_ctxt *ctxt)
 	struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);

 	vcpu->arch.hflags &= ~(HF_SMM_MASK | HF_SMM_INSIDE_NMI_MASK);
-	kvm_mmu_reset_context(vcpu);
+	kvm_smm_changed(vcpu);
 }

 static int emulator_pre_leave_smm(struct x86_emulate_ctxt *ctxt,
@@ -7120,7 +7120,7 @@ static int emulator_pre_leave_smm(struct x86_emulate_ctxt *ctxt,

 static void emulator_post_leave_smm(struct x86_emulate_ctxt *ctxt)
 {
-	kvm_smm_changed(emul_to_vcpu(ctxt));
+	kvm_mmu_reset_context(emul_to_vcpu(ctxt));
 }

 static void emulator_triple_fault(struct x86_emulate_ctxt *ctxt)
-- 
2.32.0.rc1.229.g3e70b5a671-goog