From nobody Wed Dec 17 12:08:41 2025 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D47A81E0DE2; Fri, 28 Mar 2025 17:13:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743181998; cv=none; b=ixjipihNwu8P7/+q2HgnV94B4QtN5Ch23mQ1eSYoNUDDT/jGp9adSNwnfJT9TI4oBx8lY6qdTnJruD/y5aqQ+Y3FRY3yYxB9t5G+UFGtRNcfG27rvua3/JiAyJ4a09rhkuVkSvf9ookq+2Wup6Gq2M7cu+NzJTngYTu1/vuvxRc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743181998; c=relaxed/simple; bh=sORkSZIXkdOTUrIEh48zIdJe0yhkLLYsXztU7eYPrPw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uIF1GKp+6nLcZAbfyFn86r0R7Ga1w/wIFfTYLNGT3vnNlZOFeyaqzCagYR02UkB3vFLAo5iplWxBLop4dDiS6FWfaGCNhU5nFMfWcyxOKmsYxP2lnCLdmh1Z39OUNY2jV2ZiqT96Tc8jzhHlYHCbimeVrze3ggqaCbUF1ahIIYw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=LylFpn+b; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="LylFpn+b" Received: from terminus.zytor.com (terminus.zytor.com [IPv6:2607:7c80:54:3:0:0:0:136]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 52SHC6vi2029344 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Fri, 28 Mar 2025 10:12:25 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 52SHC6vi2029344 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025032001; t=1743181945; bh=mzkjBiaEYOeYYghsQnvYoR2QI96dNfDwMXS5aEW6BXs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LylFpn+blP+nd+Y8z95On+RLPS56AkPmrDsbMswc/QqBEXR3MM1HW5/GcpdE/P5MQ wwZ+KeKUwgiffdgRoWwXT8AtRk6cVms2AFYp0bGpJFx+Ap7ShSZ+/rIDFGu0K+h/Z6 9F02hk+KHpJqDRCQNMCI/Y38M1n6RxDYo35pIYQAhVeQ8dA8mv7d4I8Rqmhuabsr1Q D6YKYLUpW+NXFOEA1LYvML2Oc3EHECt/ZcmAxwejLMgkd6fsTQo7+URhYoywh7f6nV 072uX0IVHHwBzyaTQmGtI0LqTMp/3f8pTgiXTNHk/r/vpnck1G1OmXcoWuaHFfqdwV BVB0xB0G6RULA== From: "Xin Li (Intel)" To: pbonzini@redhat.com, seanjc@google.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Cc: corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, andrew.cooper3@citrix.com, luto@kernel.org, peterz@infradead.org, chao.gao@intel.com, xin3.li@intel.com Subject: [PATCH v4 12/19] KVM: x86: Save/restore the nested flag of an exception Date: Fri, 28 Mar 2025 10:11:58 -0700 Message-ID: <20250328171205.2029296-13-xin@zytor.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250328171205.2029296-1-xin@zytor.com> References: <20250328171205.2029296-1-xin@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Save/restore the nested flag of an exception during VM save/restore and live migration to ensure a correct event stack level is chosen when a nested exception is injected through FRED event delivery. Signed-off-by: Xin Li (Intel) --- Change in v4: * Add live migration support for exception nested flag (Chao Gao). --- Documentation/virt/kvm/api.rst | 19 +++++++++++++++++++ arch/x86/include/asm/kvm_host.h | 1 + arch/x86/include/uapi/asm/kvm.h | 4 +++- arch/x86/kvm/x86.c | 19 ++++++++++++++++++- include/uapi/linux/kvm.h | 1 + 5 files changed, 42 insertions(+), 2 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 1f8625b7646a..32c00b07bcf1 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -1184,6 +1184,10 @@ The following bits are defined in the flags field: fields contain a valid state. This bit will be set whenever KVM_CAP_EXCEPTION_PAYLOAD is enabled. =20 +- KVM_VCPUEVENT_VALID_NESTED_FLAG may be set to inform that the + exception is a nested exception. This bit will be set whenever + KVM_CAP_EXCEPTION_NESTED_FLAG is enabled. + - KVM_VCPUEVENT_VALID_TRIPLE_FAULT may be set to signal that the triple_fault_pending field contains a valid state. This bit will be set whenever KVM_CAP_X86_TRIPLE_FAULT_EVENT is enabled. @@ -1283,6 +1287,10 @@ can be set in the flags field to signal that the exception_has_payload, exception_payload, and exception.pending fields contain a valid state and shall be written into the VCPU. =20 +If KVM_CAP_EXCEPTION_NESTED_FLAG is enabled, KVM_VCPUEVENT_VALID_NESTED_FL= AG +can be set in the flags field to inform that the exception is a nested +exception and exception_is_nested shall be written into the VCPU. + If KVM_CAP_X86_TRIPLE_FAULT_EVENT is enabled, KVM_VCPUEVENT_VALID_TRIPLE_F= AULT can be set in flags field to signal that the triple_fault field contains a valid state and shall be written into the VCPU. @@ -8280,6 +8288,17 @@ aforementioned registers before the first KVM_RUN. T= hese registers are VM scoped, meaning that the same set of values are presented on all vCPUs in a given VM. =20 +7.38 KVM_CAP_EXCEPTION_NESTED_FLAG +---------------------------------- + +:Architectures: x86 +:Parameters: args[0] whether feature should be enabled or not + +With this capability enabled, an exception is save/restored with the +additional information of whether it was nested or not. FRED event +delivery uses this information to ensure a correct event stack level +is chosen when a VM entry injects a nested exception. + 8. Other capabilities. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =20 diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_hos= t.h index c5f92a1befc0..f8b9834f2f37 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1444,6 +1444,7 @@ struct kvm_arch { =20 bool guest_can_read_msr_platform_info; bool exception_payload_enabled; + bool exception_nested_flag_enabled; =20 bool triple_fault_event; =20 diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kv= m.h index 460306b35a4b..6a3a39d04843 100644 --- a/arch/x86/include/uapi/asm/kvm.h +++ b/arch/x86/include/uapi/asm/kvm.h @@ -326,6 +326,7 @@ struct kvm_reinject_control { #define KVM_VCPUEVENT_VALID_SMM 0x00000008 #define KVM_VCPUEVENT_VALID_PAYLOAD 0x00000010 #define KVM_VCPUEVENT_VALID_TRIPLE_FAULT 0x00000020 +#define KVM_VCPUEVENT_VALID_NESTED_FLAG 0x00000040 =20 /* Interrupt shadow states */ #define KVM_X86_SHADOW_INT_MOV_SS 0x01 @@ -363,7 +364,8 @@ struct kvm_vcpu_events { struct { __u8 pending; } triple_fault; - __u8 reserved[26]; + __u8 reserved[25]; + __u8 exception_is_nested; __u8 exception_has_payload; __u64 exception_payload; }; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7f013ff97067..17b5a799f65d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4710,6 +4710,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, lon= g ext) case KVM_CAP_GET_MSR_FEATURES: case KVM_CAP_MSR_PLATFORM_INFO: case KVM_CAP_EXCEPTION_PAYLOAD: + case KVM_CAP_EXCEPTION_NESTED_FLAG: case KVM_CAP_X86_TRIPLE_FAULT_EVENT: case KVM_CAP_SET_GUEST_DEBUG: case KVM_CAP_LAST_CPU: @@ -5437,6 +5438,7 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct= kvm_vcpu *vcpu, events->exception.error_code =3D ex->error_code; events->exception_has_payload =3D ex->has_payload; events->exception_payload =3D ex->payload; + events->exception_is_nested =3D ex->nested; =20 events->interrupt.injected =3D vcpu->arch.interrupt.injected && !vcpu->arch.interrupt.soft; @@ -5462,6 +5464,8 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct= kvm_vcpu *vcpu, | KVM_VCPUEVENT_VALID_SMM); if (vcpu->kvm->arch.exception_payload_enabled) events->flags |=3D KVM_VCPUEVENT_VALID_PAYLOAD; + if (vcpu->kvm->arch.exception_nested_flag_enabled) + events->flags |=3D KVM_VCPUEVENT_VALID_NESTED_FLAG; if (vcpu->kvm->arch.triple_fault_event) { events->triple_fault.pending =3D kvm_test_request(KVM_REQ_TRIPLE_FAULT, = vcpu); events->flags |=3D KVM_VCPUEVENT_VALID_TRIPLE_FAULT; @@ -5476,7 +5480,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct = kvm_vcpu *vcpu, | KVM_VCPUEVENT_VALID_SHADOW | KVM_VCPUEVENT_VALID_SMM | KVM_VCPUEVENT_VALID_PAYLOAD - | KVM_VCPUEVENT_VALID_TRIPLE_FAULT)) + | KVM_VCPUEVENT_VALID_TRIPLE_FAULT + | KVM_VCPUEVENT_VALID_NESTED_FLAG)) return -EINVAL; =20 if (events->flags & KVM_VCPUEVENT_VALID_PAYLOAD) { @@ -5491,6 +5496,13 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct= kvm_vcpu *vcpu, events->exception_has_payload =3D 0; } =20 + if (events->flags & KVM_VCPUEVENT_VALID_NESTED_FLAG) { + if (!vcpu->kvm->arch.exception_nested_flag_enabled) + return -EINVAL; + } else { + events->exception_is_nested =3D 0; + } + if ((events->exception.injected || events->exception.pending) && (events->exception.nr > 31 || events->exception.nr =3D=3D NMI_VECTOR)) return -EINVAL; @@ -5522,6 +5534,7 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct = kvm_vcpu *vcpu, vcpu->arch.exception.error_code =3D events->exception.error_code; vcpu->arch.exception.has_payload =3D events->exception_has_payload; vcpu->arch.exception.payload =3D events->exception_payload; + vcpu->arch.exception.nested =3D events->exception_is_nested; =20 vcpu->arch.interrupt.injected =3D events->interrupt.injected; vcpu->arch.interrupt.nr =3D events->interrupt.nr; @@ -6644,6 +6657,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, kvm->arch.exception_payload_enabled =3D cap->args[0]; r =3D 0; break; + case KVM_CAP_EXCEPTION_NESTED_FLAG: + kvm->arch.exception_nested_flag_enabled =3D cap->args[0]; + r =3D 0; + break; case KVM_CAP_X86_TRIPLE_FAULT_EVENT: kvm->arch.triple_fault_event =3D cap->args[0]; r =3D 0; diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index b6ae8ad8934b..5ef33256858f 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -930,6 +930,7 @@ struct kvm_enable_cap { #define KVM_CAP_X86_APIC_BUS_CYCLES_NS 237 #define KVM_CAP_X86_GUEST_MODE 238 #define KVM_CAP_ARM_WRITABLE_IMP_ID_REGS 239 +#define KVM_CAP_EXCEPTION_NESTED_FLAG 240 =20 struct kvm_irq_routing_irqchip { __u32 irqchip; --=20 2.48.1