linux-kernel - [PATCH v2 04/11] KVM: x86: emulator: update the emulation mode after rsm

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Message-Id: <20220621150902.46126-5-mlevitsk@redhat.com>
Date:   Tue, 21 Jun 2022 18:08:55 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
        Borislav Petkov <bp@...en8.de>, Joerg Roedel <joro@...tes.org>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH v2 04/11] KVM: x86: emulator: update the emulation mode after rsm

This ensures that RIP will be correctly written back,
because the RSM instruction can switch the CPU mode from
32 bit (or less) to 64 bit.

This fixes a guest crash in case the #SMI is received
while the guest runs a code from an address > 32 bit.

Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
---
 arch/x86/kvm/emulate.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 334a06e6c9b093..6f4632babc4cd8 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2662,6 +2662,11 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
 	if (ret != X86EMUL_CONTINUE)
 		goto emulate_shutdown;
 
+
+	ret = update_emulation_mode(ctxt);
+	if (ret != X86EMUL_CONTINUE)
+		goto emulate_shutdown;
+
 	/*
 	 * Note, the ctxt->ops callbacks are responsible for handling side
 	 * effects when writing MSRs and CRs, e.g. MMU context resets, CPUID
-- 
2.26.3