linux-kernel - [PATCH v3 3/7] KVM: x86: Unprotect & retry before unhandleable vectoring check

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Message-ID: <20241217181458.68690-4-iorlov@amazon.com>
Date: Tue, 17 Dec 2024 18:14:54 +0000
From: Ivan Orlov <iorlov@...zon.com>
To: <bp@...en8.de>, <dave.hansen@...ux.intel.com>, <mingo@...hat.com>,
	<pbonzini@...hat.com>, <seanjc@...gle.com>, <shuah@...nel.org>,
	<tglx@...utronix.de>
CC: Ivan Orlov <iorlov@...zon.com>, <hpa@...or.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-kselftest@...r.kernel.org>,
	<x86@...nel.org>, <dwmw@...zon.co.uk>, <pdurrant@...zon.co.uk>,
	<jalliste@...zon.co.uk>
Subject: [PATCH v3 3/7] KVM: x86: Unprotect & retry before unhandleable vectoring check

Try to unprotect and retry the instruction execution before checking for
unhandleable vectoring. If there is a write to a shadowed page table
when vectoring an event, KVM should be able to unprotect the gfn and
retry the instruction execution without returning an error to userspace.

This ensures that the subsequent patches won't make KVM exit to
userspace when handling an intercepted #PF during vectoring without
checking whether unprotect & retry is possible.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Ivan Orlov <iorlov@...zon.com>
---
V1 -> V2:
- This patch wasn't included in V1.
V2 -> V3:
- This patch wasn't included in V2.

 arch/x86/kvm/x86.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 849a6fc364b3..26faacc99c4c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9107,6 +9107,10 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 		if (r == X86EMUL_RETRY_INSTR || r == X86EMUL_PROPAGATE_FAULT)
 			return 1;
 
+		if (kvm_unprotect_and_retry_on_failure(vcpu, cr2_or_gpa,
+						       emulation_type))
+			return 1;
+
 		if (r == X86EMUL_UNHANDLEABLE_VECTORING) {
 			kvm_prepare_event_vectoring_exit(vcpu, cr2_or_gpa);
 			return 0;
-- 
2.43.0