[PATCH v2 07/10] KVM: VMX: Introduce test mode related to EPT violation VE
From: Paolo Bonzini
Date: Tue Apr 16 2024 - 16:23:14 EST
From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
To support TDX, KVM is enhanced to operate with #VE. For TDX, KVM uses the
suppress #VE bit in EPT entries selectively, in order to be able to trap
non-present conditions. However, #VE isn't used for VMX and it's a bug
if it happens. To be defensive and test that VMX case isn't broken
introduce an option ept_violation_ve_test and when it's set, BUG the vm.
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Message-Id: <d6db6ba836605c0412e166359ba5c46a63c22f86.1705965635.git.isaku.yamahata@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/Kconfig | 13 ++++++++++++
arch/x86/kvm/vmx/vmcs.h | 5 +++++
arch/x86/kvm/vmx/vmx.c | 47 ++++++++++++++++++++++++++++++++++++++++-
arch/x86/kvm/vmx/vmx.h | 6 +++++-
4 files changed, 69 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 3aaf7e86a859..7632fe6e4db9 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -95,6 +95,19 @@ config KVM_INTEL
To compile this as a module, choose M here: the module
will be called kvm-intel.
+config KVM_INTEL_PROVE_VE
+ bool "Check that guests do not receive #VE exceptions"
+ default KVM_PROVE_MMU || DEBUG_KERNEL
+ depends on KVM_INTEL
+ help
+
+ Checks that KVM's page table management code will not incorrectly
+ let guests receive a virtualization exception. Virtualization
+ exceptions will be trapped by the hypervisor rather than injected
+ in the guest.
+
+ If unsure, say N.
+
config X86_SGX_KVM
bool "Software Guard eXtensions (SGX) Virtualization"
depends on X86_SGX && KVM_INTEL
diff --git a/arch/x86/kvm/vmx/vmcs.h b/arch/x86/kvm/vmx/vmcs.h
index 7c1996b433e2..b25625314658 100644
--- a/arch/x86/kvm/vmx/vmcs.h
+++ b/arch/x86/kvm/vmx/vmcs.h
@@ -140,6 +140,11 @@ static inline bool is_nm_fault(u32 intr_info)
return is_exception_n(intr_info, NM_VECTOR);
}
+static inline bool is_ve_fault(u32 intr_info)
+{
+ return is_exception_n(intr_info, VE_VECTOR);
+}
+
/* Undocumented: icebp/int1 */
static inline bool is_icebp(u32 intr_info)
{
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 2c746318c6c3..3c2fb1310aaa 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -869,6 +869,12 @@ void vmx_update_exception_bitmap(struct kvm_vcpu *vcpu)
eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) |
(1u << DB_VECTOR) | (1u << AC_VECTOR);
+ /*
+ * #VE isn't used for VMX. To test against unexpected changes
+ * related to #VE for VMX, intercept unexpected #VE and warn on it.
+ */
+ if (IS_ENABLED(CONFIG_KVM_INTEL_PROVE_VE))
+ eb |= 1u << VE_VECTOR;
/*
* Guest access to VMware backdoor ports could legitimately
* trigger #GP because of TSS I/O permission bitmap.
@@ -2602,6 +2608,9 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
&_cpu_based_2nd_exec_control))
return -EIO;
}
+ if (!IS_ENABLED(CONFIG_KVM_INTEL_PROVE_VE))
+ _cpu_based_2nd_exec_control &= ~SECONDARY_EXEC_EPT_VIOLATION_VE;
+
#ifndef CONFIG_X86_64
if (!(_cpu_based_2nd_exec_control &
SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES))
@@ -2626,6 +2635,7 @@ static int setup_vmcs_config(struct vmcs_config *vmcs_conf,
return -EIO;
vmx_cap->ept = 0;
+ _cpu_based_2nd_exec_control &= ~SECONDARY_EXEC_EPT_VIOLATION_VE;
}
if (!(_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_VPID) &&
vmx_cap->vpid) {
@@ -4588,6 +4598,7 @@ static u32 vmx_secondary_exec_control(struct vcpu_vmx *vmx)
exec_control &= ~SECONDARY_EXEC_ENABLE_VPID;
if (!enable_ept) {
exec_control &= ~SECONDARY_EXEC_ENABLE_EPT;
+ exec_control &= ~SECONDARY_EXEC_EPT_VIOLATION_VE;
enable_unrestricted_guest = 0;
}
if (!enable_unrestricted_guest)
@@ -4711,8 +4722,21 @@ static void init_vmcs(struct vcpu_vmx *vmx)
exec_controls_set(vmx, vmx_exec_control(vmx));
- if (cpu_has_secondary_exec_ctrls())
+ if (cpu_has_secondary_exec_ctrls()) {
secondary_exec_controls_set(vmx, vmx_secondary_exec_control(vmx));
+ if (vmx->ve_info) {
+ vmcs_write64(VE_INFORMATION_ADDRESS,
+ __pa(vmx->ve_info));
+ } else {
+ /*
+ * Because SECONDARY_EXEC_EPT_VIOLATION_VE is
+ * used only for debugging, it's okay to leave
+ * it disabled.
+ */
+ secondary_exec_controls_clearbit(vmx,
+ SECONDARY_EXEC_EPT_VIOLATION_VE);
+ }
+ }
if (cpu_has_tertiary_exec_ctrls())
tertiary_exec_controls_set(vmx, vmx_tertiary_exec_control(vmx));
@@ -5200,6 +5224,12 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
if (is_invalid_opcode(intr_info))
return handle_ud(vcpu);
+ /*
+ * #VE isn't supposed to happen. Block the VM if it does.
+ */
+ if (KVM_BUG_ON(is_ve_fault(intr_info), vcpu->kvm))
+ return -EIO;
+
error_code = 0;
if (intr_info & INTR_INFO_DELIVER_CODE_MASK)
error_code = vmcs_read32(VM_EXIT_INTR_ERROR_CODE);
@@ -7474,6 +7504,8 @@ void vmx_vcpu_free(struct kvm_vcpu *vcpu)
free_vpid(vmx->vpid);
nested_vmx_free_vcpu(vcpu);
free_loaded_vmcs(vmx->loaded_vmcs);
+ if (vmx->ve_info)
+ free_page((unsigned long)vmx->ve_info);
}
int vmx_vcpu_create(struct kvm_vcpu *vcpu)
@@ -7567,6 +7599,19 @@ int vmx_vcpu_create(struct kvm_vcpu *vcpu)
goto free_vmcs;
}
+ if (vmcs_config.cpu_based_2nd_exec_ctrl & SECONDARY_EXEC_EPT_VIOLATION_VE) {
+ struct page *page;
+
+ BUILD_BUG_ON(sizeof(*vmx->ve_info) > PAGE_SIZE);
+
+ /* ve_info must be page aligned. */
+ page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+ if (page)
+ vmx->ve_info = page_to_virt(page);
+ else
+ pr_err("Failed to allocate ve_info. disabling EPT_VIOLATION_VE.\n");
+ }
+
if (vmx_can_use_ipiv(vcpu))
WRITE_ONCE(to_kvm_vmx(vcpu->kvm)->pid_table[vcpu->vcpu_id],
__pa(&vmx->pi_desc) | PID_TABLE_ENTRY_VALID);
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 65786dbe7d60..0da79a386825 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -362,6 +362,9 @@ struct vcpu_vmx {
DECLARE_BITMAP(read, MAX_POSSIBLE_PASSTHROUGH_MSRS);
DECLARE_BITMAP(write, MAX_POSSIBLE_PASSTHROUGH_MSRS);
} shadow_msr_intercept;
+
+ /* ve_info must be page aligned. */
+ struct vmx_ve_information *ve_info;
};
struct kvm_vmx {
@@ -574,7 +577,8 @@ static inline u8 vmx_get_rvi(void)
SECONDARY_EXEC_ENABLE_VMFUNC | \
SECONDARY_EXEC_BUS_LOCK_DETECTION | \
SECONDARY_EXEC_NOTIFY_VM_EXITING | \
- SECONDARY_EXEC_ENCLS_EXITING)
+ SECONDARY_EXEC_ENCLS_EXITING | \
+ SECONDARY_EXEC_EPT_VIOLATION_VE)
#define KVM_REQUIRED_VMX_TERTIARY_VM_EXEC_CONTROL 0
#define KVM_OPTIONAL_VMX_TERTIARY_VM_EXEC_CONTROL \
--
2.43.0