From: Sohil Mehta <sohil.mehta@intel.com>
To: kvm@vger.kernel.org, x86@kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Shuah Khan <skhan@linuxfoundation.org>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H . Peter Anvin" <hpa@zytor.com>, Xin Li <xin@zytor.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Nikunj A Dadhania <nikunj@amd.com>,
Shivansh Dhiman <shivansh.dhiman@amd.com>,
David Woodhouse <dwmw@amazon.co.uk>,
Chao Gao <chao.gao@intel.com>,
Binbin Wu <binbin.wu@linux.intel.com>,
Sohil Mehta <sohil.mehta@intel.com>,
Zhao Liu <zhao1.liu@intel.com>, Yosry Ahmed <yosry@kernel.org>,
David Matlack <dmatlack@google.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org
Subject: [PATCH v10 24/28] KVM: nVMX: Validate FRED-related VMCS fields
Date: Fri, 11 Sep 2026 14:36:54 -0700 [thread overview]
Message-ID: <20260911213659.2025974-25-sohil.mehta@intel.com> (raw)
In-Reply-To: <20260911213659.2025974-1-sohil.mehta@intel.com>
From: "Xin Li (Intel)" <xin@zytor.com>
Extend nested VMX field validation to include FRED-specific VMCS fields,
mirroring hardware behavior.
This enables support for nested FRED by ensuring control and guest/host
state fields are properly checked.
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
---
v10:
- Use has_nested_exception to describe the event being injected rather
than the CPU capability, for consistency with has_error_code (Chao).
- Restructure the interruption-information checks into a switch on the
interruption type (Chao).
- Add a CC() statement to the reserved interruption type check so a
VM-entry failure can be correlated with a specific check (Chao).
- Reject the nested-exception bit (bit 13) for interruption types other
than hardware exception, and fold in the nested-exception capability
check.
- Bound the "other event" vector explicitly instead of relying on a
default arm.
- Reject a zero VM-entry instruction length when injecting SYSCALL or
SYSENTER if the vCPU doesn't enumerate zero-length instruction
injection.
---
arch/x86/kvm/vmx/nested.c | 119 +++++++++++++++++++++++++++++++++-----
arch/x86/kvm/vmx/nested.h | 5 ++
2 files changed, 111 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 83e846fb3fc8..3e0a1ed6440d 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3111,6 +3111,8 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
struct vmcs12 *vmcs12)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
+ bool fred_enabled = (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) &&
+ (vmcs12->guest_cr4 & X86_CR4_FRED);
if (CC(!vmx_control_verify(vmcs12->vm_entry_controls,
vmx->nested.msrs.entry_ctls_low,
@@ -3128,22 +3130,11 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
u8 vector = intr_info & INTR_INFO_VECTOR_MASK;
u32 intr_type = intr_info & INTR_INFO_INTR_TYPE_MASK;
bool has_error_code = intr_info & INTR_INFO_DELIVER_CODE_MASK;
+ bool has_nested_exception = intr_info & INTR_INFO_NESTED_EXCEPTION_MASK;
bool urg = nested_cpu_has2(vmcs12,
SECONDARY_EXEC_UNRESTRICTED_GUEST);
bool prot_mode = !urg || vmcs12->guest_cr0 & X86_CR0_PE;
- /* VM-entry interruption-info field: interruption type */
- if (CC(intr_type == INTR_TYPE_RESERVED) ||
- CC(intr_type == INTR_TYPE_OTHER_EVENT &&
- !nested_cpu_supports_monitor_trap_flag(vcpu)))
- return -EINVAL;
-
- /* VM-entry interruption-info field: vector */
- if (CC(intr_type == INTR_TYPE_NMI_INTR && vector != NMI_VECTOR) ||
- CC(intr_type == INTR_TYPE_HARD_EXCEPTION && vector > 31) ||
- CC(intr_type == INTR_TYPE_OTHER_EVENT && vector != 0))
- return -EINVAL;
-
/*
* Cannot deliver error code in real mode or if the interrupt
* type is not hardware exception. For other cases, do the
@@ -3167,8 +3158,28 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
if (CC(intr_info & INTR_INFO_RESVD_BITS_MASK))
return -EINVAL;
- /* VM-entry instruction length */
+ if (CC(intr_type == INTR_TYPE_RESERVED))
+ return -EINVAL;
+
+ /*
+ * Only for hardware exceptions and when the CPU enumerates
+ * VMX nested-exception support, bit 13 (indicating a nested
+ * exception) has value 1. Otherwise it is reserved.
+ */
+ if (CC(has_nested_exception &&
+ (intr_type != INTR_TYPE_HARD_EXCEPTION ||
+ !nested_cpu_has_nested_exception(vcpu))))
+ return -EINVAL;
+
switch (intr_type) {
+ case INTR_TYPE_NMI_INTR:
+ if (CC(vector != NMI_VECTOR))
+ return -EINVAL;
+ break;
+ case INTR_TYPE_HARD_EXCEPTION:
+ if (CC(vector > 31))
+ return -EINVAL;
+ break;
case INTR_TYPE_SOFT_EXCEPTION:
case INTR_TYPE_SOFT_INTR:
case INTR_TYPE_PRIV_SW_EXCEPTION:
@@ -3176,6 +3187,28 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
CC(vmcs12->vm_entry_instruction_len == 0 &&
CC(!nested_cpu_has_zero_length_injection(vcpu))))
return -EINVAL;
+ break;
+ case INTR_TYPE_OTHER_EVENT:
+ if (CC(vector > 2))
+ return -EINVAL;
+
+ switch (vector) {
+ case 0:
+ if (CC(!nested_cpu_supports_monitor_trap_flag(vcpu)))
+ return -EINVAL;
+ break;
+ case 1:
+ case 2:
+ if (CC(!fred_enabled))
+ return -EINVAL;
+ if (CC(vmcs12->vm_entry_instruction_len > X86_MAX_INSTRUCTION_LENGTH))
+ return -EINVAL;
+ if (CC(vmcs12->vm_entry_instruction_len == 0 &&
+ !nested_cpu_has_zero_length_injection(vcpu)))
+ return -EINVAL;
+ break;
+ }
+ break;
}
}
@@ -3262,9 +3295,27 @@ static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
if (ia32e) {
if (CC(!(vmcs12->host_cr4 & X86_CR4_PAE)))
return -EINVAL;
+ if (nested_cpu_load_host_fred_state(vmcs12)) {
+ if (CC(vmcs12->host_ia32_fred_config & FRED_CONFIG_RESERVED) ||
+ CC(vmcs12->host_ia32_fred_rsp1 & GENMASK_ULL(5, 0)) ||
+ CC(vmcs12->host_ia32_fred_rsp2 & GENMASK_ULL(5, 0)) ||
+ CC(vmcs12->host_ia32_fred_rsp3 & GENMASK_ULL(5, 0)) ||
+ CC(vmcs12->host_ia32_fred_ssp1 & GENMASK_ULL(2, 0)) ||
+ CC(vmcs12->host_ia32_fred_ssp2 & GENMASK_ULL(2, 0)) ||
+ CC(vmcs12->host_ia32_fred_ssp3 & GENMASK_ULL(2, 0)) ||
+ CC(is_noncanonical_msr_address(vmcs12->host_ia32_fred_config & PAGE_MASK, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->host_ia32_fred_rsp1, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->host_ia32_fred_rsp2, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->host_ia32_fred_rsp3, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->host_ia32_fred_ssp1, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->host_ia32_fred_ssp2, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->host_ia32_fred_ssp3, vcpu)))
+ return -EINVAL;
+ }
} else {
if (CC(vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) ||
CC(vmcs12->host_cr4 & X86_CR4_PCIDE) ||
+ CC(vmcs12->host_cr4 & X86_CR4_FRED) ||
CC((vmcs12->host_rip) >> 32))
return -EINVAL;
}
@@ -3447,6 +3498,48 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu,
CC((vmcs12->guest_bndcfgs & MSR_IA32_BNDCFGS_RSVD))))
return -EINVAL;
+ if (ia32e) {
+ if (nested_cpu_load_guest_fred_state(vmcs12)) {
+ if (CC(vmcs12->guest_ia32_fred_config & FRED_CONFIG_RESERVED) ||
+ CC(vmcs12->guest_ia32_fred_rsp1 & GENMASK_ULL(5, 0)) ||
+ CC(vmcs12->guest_ia32_fred_rsp2 & GENMASK_ULL(5, 0)) ||
+ CC(vmcs12->guest_ia32_fred_rsp3 & GENMASK_ULL(5, 0)) ||
+ CC(vmcs12->guest_ia32_fred_ssp1 & GENMASK_ULL(2, 0)) ||
+ CC(vmcs12->guest_ia32_fred_ssp2 & GENMASK_ULL(2, 0)) ||
+ CC(vmcs12->guest_ia32_fred_ssp3 & GENMASK_ULL(2, 0)) ||
+ CC(is_noncanonical_msr_address(vmcs12->guest_ia32_fred_config & PAGE_MASK, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->guest_ia32_fred_rsp1, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->guest_ia32_fred_rsp2, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->guest_ia32_fred_rsp3, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->guest_ia32_fred_ssp1, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->guest_ia32_fred_ssp2, vcpu)) ||
+ CC(is_noncanonical_msr_address(vmcs12->guest_ia32_fred_ssp3, vcpu)))
+ return -EINVAL;
+ }
+ if (vmcs12->guest_cr4 & X86_CR4_FRED) {
+ unsigned int ss_dpl = VMX_AR_DPL(vmcs12->guest_ss_ar_bytes);
+
+ if (CC(ss_dpl == 1 || ss_dpl == 2))
+ return -EINVAL;
+
+ switch (ss_dpl) {
+ case 0:
+ if (CC(!(vmcs12->guest_cs_ar_bytes & VMX_AR_L_MASK)))
+ return -EINVAL;
+ break;
+ case 3:
+ if (CC(vmcs12->guest_rflags & X86_EFLAGS_IOPL))
+ return -EINVAL;
+ if (CC(vmcs12->guest_interruptibility_info & GUEST_INTR_STATE_STI))
+ return -EINVAL;
+ break;
+ }
+ }
+ } else {
+ if (CC(vmcs12->guest_cr4 & X86_CR4_FRED))
+ return -EINVAL;
+ }
+
if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE) {
if (nested_vmx_check_cet_state_common(vcpu, vmcs12->guest_s_cet,
vmcs12->guest_ssp,
diff --git a/arch/x86/kvm/vmx/nested.h b/arch/x86/kvm/vmx/nested.h
index dc5a1e9cb4e9..551121824128 100644
--- a/arch/x86/kvm/vmx/nested.h
+++ b/arch/x86/kvm/vmx/nested.h
@@ -334,6 +334,11 @@ static inline bool nested_cpu_has_no_hw_errcode_cc(struct kvm_vcpu *vcpu)
return to_vmx(vcpu)->nested.msrs.basic & VMX_BASIC_NO_HW_ERROR_CODE_CC;
}
+static inline bool nested_cpu_has_nested_exception(struct kvm_vcpu *vcpu)
+{
+ return to_vmx(vcpu)->nested.msrs.basic & VMX_BASIC_NESTED_EXCEPTION;
+}
+
/* No difference in the restrictions on guest and host CR4 in VMX operation. */
#define nested_guest_cr4_valid nested_cr4_valid
#define nested_host_cr4_valid nested_cr4_valid
--
2.43.0
next prev parent reply other threads:[~2026-09-11 21:43 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-11 21:36 [PATCH v10 00/28] KVM: Enable FRED support with KVM VMX Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 01/28] KVM: VMX: Enable support for secondary VM exit controls Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 02/28] KVM: VMX: Initialize VM entry/exit FRED controls in vmcs_config Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 03/28] KVM: VMX: Disable FRED if FRED consistency checks fail Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 04/28] x86/cea: Prefix event stack names with ESTACK_ Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 05/28] x86/cea: Use array indexing to simplify exception stack access Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 06/28] x86/fred: Export this_cpu_fred_rsp() for KVM usage Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 07/28] KVM: VMX: Initialize VMCS FRED fields Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 08/28] KVM: VMX: Set FRED MSR intercepts Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 09/28] KVM: VMX: Save/restore guest FRED RSP0 Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 10/28] KVM: VMX: Add support for saving and restoring FRED MSRs Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 11/28] KVM: x86: Add a helper to detect if FRED is enabled for a vCPU Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 12/28] KVM: x86: Add a new save/restore flag for FRED metadata Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 13/28] KVM: VMX: Virtualize FRED nested exception tracking Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 14/28] KVM: VMX: Virtualize FRED event_data Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 15/28] KVM: x86: Include CR4.FRED in the emulator CR4 write mask Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 16/28] KVM: x86: Mark CR4.FRED as not reserved Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 17/28] KVM: x86: Handle CR4.FRED when emulating RSM Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 18/28] KVM: VMX: Dump FRED context in dump_vmcs() Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 19/28] KVM: x86: Advertise support for FRED Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 20/28] KVM: nVMX: Enable support for secondary VM exit controls Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 21/28] KVM: nVMX: Handle FRED VMCS fields in nested VMX context Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 22/28] KVM: nVMX: Restrict event data VMCS fields to FRED-supported hosts Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 23/28] KVM: nVMX: Shadow ORIGINAL_EVENT_DATA and INJECTED_EVENT_DATA fields Sohil Mehta
2026-09-11 21:36 ` Sohil Mehta [this message]
2026-09-11 21:36 ` [PATCH v10 25/28] KVM: nVMX: Enable VMX FRED controls Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 26/28] KVM: selftests: Add FRED MSRs to msrs_test Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 27/28] KVM: selftests: Add a new VM guest mode to run user level code Sohil Mehta
2026-09-11 21:36 ` [PATCH v10 28/28] KVM: selftests: Add fred exception tests Sohil Mehta
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