Re: [PATCH 01/22] KVM: TDX/VMX: rework EPT_VIOLATION_EXEC_FOR_RING3_LIN into PROT_MASK

[Jon Kohler <jon@nutanix.com>]

> On Mar 20, 2026, at 8:09 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
> From: Jon Kohler <jon@nutanix.com>
> 
> EPT exit qualification bit 6 is used when mode-based execute control
> is enabled, and reflects user executable addresses. Rework name to
> reflect the intention and add to EPT_VIOLATION_PROT_MASK, which allows
> simplifying the return evaluation in
> tdx_is_sept_violation_unexpected_pending a pinch.
> 
> Rework handling in __vmx_handle_ept_violation to unconditionally clear
> EPT_VIOLATION_PROT_USER_EXEC until MBEC is implemented, as suggested by
> Sean [1].
> 
> Note: Intel SDM Table 29-7 defines bit 6 as:
>  If the “mode-based execute control�? VM-execution control is 0, the

These quote marks should be " - utf silliness afoot ! 

>  value of this bit is undefined. If that control is 1, this bit is the
>  logical-AND of bit 10 in the EPT paging-structure entries used to
>  translate the guest-physical address of the access causing the EPT
>  violation. In this case, it indicates whether the guest-physical
>  address was executable for user-mode linear addresses.
> 
> [1] https://lore.kernel.org/all/aCJDzU1p_SFNRIJd@google.com/ 
> 
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Jon Kohler <jon@nutanix.com>
> Message-ID: <20251223054806.1611168-2-jon@nutanix.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> arch/x86/include/asm/vmx.h | 5 +++--
> arch/x86/kvm/vmx/common.h  | 9 +++++++--
> arch/x86/kvm/vmx/tdx.c     | 2 +-
> 3 files changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index cca7d6641287..4a0804cc7c82 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -587,10 +587,11 @@ enum vm_entry_failure_code {
> #define EPT_VIOLATION_PROT_READ BIT(3)
> #define EPT_VIOLATION_PROT_WRITE BIT(4)
> #define EPT_VIOLATION_PROT_EXEC BIT(5)
> -#define EPT_VIOLATION_EXEC_FOR_RING3_LIN BIT(6)
> +#define EPT_VIOLATION_PROT_USER_EXEC BIT(6)
> #define EPT_VIOLATION_PROT_MASK (EPT_VIOLATION_PROT_READ  | \
> EPT_VIOLATION_PROT_WRITE | \
> - EPT_VIOLATION_PROT_EXEC)
> + EPT_VIOLATION_PROT_EXEC  | \
> + EPT_VIOLATION_PROT_USER_EXEC)
> #define EPT_VIOLATION_GVA_IS_VALID BIT(7)
> #define EPT_VIOLATION_GVA_TRANSLATED BIT(8)
> 
> diff --git a/arch/x86/kvm/vmx/common.h b/arch/x86/kvm/vmx/common.h
> index 412d0829d7a2..adf925500b9e 100644
> --- a/arch/x86/kvm/vmx/common.h
> +++ b/arch/x86/kvm/vmx/common.h
> @@ -94,8 +94,13 @@ static inline int __vmx_handle_ept_violation(struct kvm_vcpu *vcpu, gpa_t gpa,
> /* Is it a fetch fault? */
> error_code |= (exit_qualification & EPT_VIOLATION_ACC_INSTR)
>      ? PFERR_FETCH_MASK : 0;
> - /* ept page table entry is present? */
> - error_code |= (exit_qualification & EPT_VIOLATION_PROT_MASK)
> + /*
> + * ept page table entry is present?
> + * note: unconditionally clear USER_EXEC until mode-based
> + * execute control is implemented
> + */
> + error_code |= (exit_qualification &
> +       (EPT_VIOLATION_PROT_MASK & ~EPT_VIOLATION_PROT_USER_EXEC))
>      ? PFERR_PRESENT_MASK : 0;
> 
> if (exit_qualification & EPT_VIOLATION_GVA_IS_VALID)
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index c308aedd8613..bf9fe76d974d 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1921,7 +1921,7 @@ static inline bool tdx_is_sept_violation_unexpected_pending(struct kvm_vcpu *vcp
> if (eeq_type != TDX_EXT_EXIT_QUAL_TYPE_PENDING_EPT_VIOLATION)
> return false;
> 
> - return !(eq & EPT_VIOLATION_PROT_MASK) && !(eq & EPT_VIOLATION_EXEC_FOR_RING3_LIN);
> + return !(eq & EPT_VIOLATION_PROT_MASK);
> }
> 
> static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu)
> -- 
> 2.52.0
>