linux-kernel - [PATCH v3 2/7] KVM: x86: Add emulation status for unhandleable vectoring

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Message-ID: <20241217181458.68690-3-iorlov@amazon.com>
Date: Tue, 17 Dec 2024 18:14:53 +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 2/7] KVM: x86: Add emulation status for unhandleable vectoring

Add emulation status for unhandleable vectoring, i.e. when KVM can't
emulate an instruction during vectoring. Such a situation can occur
if guest sets the IDT descriptor base to point to MMIO region, and
triggers an exception after that.

Exit to userspace with event delivery error when KVM can't emulate
an instruction when vectoring an event.

Signed-off-by: Ivan Orlov <iorlov@...zon.com>
---
V1 -> V2:
- This patch wasn't included in V1.
V2 -> V3:
- Make new X86EMUL_ code more generic to allow using it for any type
of unhandleable vectoring

 arch/x86/kvm/kvm_emulate.h | 2 ++
 arch/x86/kvm/x86.c         | 5 +++++
 2 files changed, 7 insertions(+)

diff --git a/arch/x86/kvm/kvm_emulate.h b/arch/x86/kvm/kvm_emulate.h
index 10495fffb890..5bcf50ffc3de 100644
--- a/arch/x86/kvm/kvm_emulate.h
+++ b/arch/x86/kvm/kvm_emulate.h
@@ -88,6 +88,8 @@ struct x86_instruction_info {
 #define X86EMUL_CMPXCHG_FAILED  4 /* cmpxchg did not see expected value */
 #define X86EMUL_IO_NEEDED       5 /* IO is needed to complete emulation */
 #define X86EMUL_INTERCEPTED     6 /* Intercepted by nested VMCB/VMCS */
+/* Vectroing can't be emulated */
+#define X86EMUL_UNHANDLEABLE_VECTORING	7
 
 /* x86-specific emulation flags */
 #define X86EMUL_F_WRITE			BIT(0)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7ce9cdb66f19..849a6fc364b3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9107,6 +9107,11 @@ 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 (r == X86EMUL_UNHANDLEABLE_VECTORING) {
+			kvm_prepare_event_vectoring_exit(vcpu, cr2_or_gpa);
+			return 0;
+		}
+
 		WARN_ON_ONCE(r != X86EMUL_UNHANDLEABLE);
 		return handle_emulation_failure(vcpu, emulation_type);
 	}
-- 
2.43.0