linux-kernel - [PATCH v3 04/13] KVM: x86: emulator: update the emulation mode after rsm

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Message-Id: <20220803155011.43721-5-mlevitsk@redhat.com>
Date:   Wed,  3 Aug 2022 18:50:02 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, Wanpeng Li <wanpengli@...cent.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        Jim Mattson <jmattson@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH v3 04/13] 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 bc70caf403c2b4..5e91b26cc1d8aa 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2666,6 +2666,11 @@ static int em_rsm(struct x86_emulate_ctxt *ctxt)
 	if (ret != X86EMUL_CONTINUE)
 		goto emulate_shutdown;
 
+
+	ret = emulator_recalc_and_set_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