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From:   Jan Dakinevich <jan.dakinevich@virtuozzo.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Jan Dakinevich <jan.dakinevich@virtuozzo.com>,
        Denis Lunev <den@virtuozzo.com>,
        Roman Kagan <rkagan@virtuozzo.com>,
        Denis Plotnikov <dplotnikov@virtuozzo.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
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        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
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        Joerg Roedel <joro@8bytes.org>,
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        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: [PATCH 3/3] KVM: x86: always stop emulation on page fault
Thread-Topic: [PATCH 3/3] KVM: x86: always stop emulation on page fault
Thread-Index: AQHVXNhVZAApmqxiJkatpVKQ81RyEQ==
Date:   Tue, 27 Aug 2019 13:07:09 +0000
Message-ID: <1566911210-30059-4-git-send-email-jan.dakinevich@virtuozzo.com>
References: <1566911210-30059-1-git-send-email-jan.dakinevich@virtuozzo.com>
In-Reply-To: <1566911210-30059-1-git-send-email-jan.dakinevich@virtuozzo.com>
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inject_emulated_exception() returns true if and only if nested page
fault happens. However, page fault can come from guest page tables
walk, either nested or not nested. In both cases we should stop an
attempt to read under RIP and give guest to step over its own page
fault handler.

Fixes: 6ea6e84 ("KVM: x86: inject exceptions produced by x86_decode_insn")
Cc: Denis Lunev <den@virtuozzo.com>
Cc: Roman Kagan <rkagan@virtuozzo.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Signed-off-by: Jan Dakinevich <jan.dakinevich@virtuozzo.com>
---
 arch/x86/kvm/x86.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 93b0bd4..45caa69 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6521,8 +6521,10 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
 			if (reexecute_instruction(vcpu, cr2, write_fault_to_spt,
 						emulation_type))
 				return EMULATE_DONE;
-			if (ctxt->have_exception && inject_emulated_exception(vcpu))
+			if (ctxt->have_exception) {
+				inject_emulated_exception(vcpu);
 				return EMULATE_DONE;
+			}
 			if (emulation_type & EMULTYPE_SKIP)
 				return EMULATE_FAIL;
 			return handle_emulation_failure(vcpu, emulation_type);
--=20
2.1.4