Re: [PATCH 1/4] kvm: x86: mmu: Use symbolic constants for EPT Violation Exit Qualifications

[Paolo Bonzini <pbonzini@redhat.com>]

On 27/10/2016 04:19, Junaid Shahid wrote:
> This change adds some symbolic constants for VM Exit Qualifications
> related to EPT Violations and updates handle_ept_violation() to use
> these constants instead of hard-coded numbers.
> 
> Signed-off-by: Junaid Shahid <junaids@google.com>
> ---
>  arch/x86/include/asm/vmx.h | 16 ++++++++++++++++
>  arch/x86/kvm/vmx.c         | 20 ++++++++++++--------
>  2 files changed, 28 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index a002b07..60991fb 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -465,6 +465,22 @@ struct vmx_msr_entry {
>  #define ENTRY_FAIL_VMCS_LINK_PTR	4
>  
>  /*
> + * Exit Qualifications for EPT Violations
> + */
> +#define EPT_VIOLATION_READ_BIT		0
> +#define EPT_VIOLATION_WRITE_BIT		1
> +#define EPT_VIOLATION_INSTR_BIT		2
> +#define EPT_VIOLATION_READABLE_BIT	3
> +#define EPT_VIOLATION_WRITABLE_BIT	4
> +#define EPT_VIOLATION_EXECUTABLE_BIT	5
> +#define EPT_VIOLATION_READ		(1 << EPT_VIOLATION_READ_BIT)
> +#define EPT_VIOLATION_WRITE		(1 << EPT_VIOLATION_WRITE_BIT)
> +#define EPT_VIOLATION_INSTR		(1 << EPT_VIOLATION_INSTR_BIT)
> +#define EPT_VIOLATION_READABLE		(1 << EPT_VIOLATION_READABLE_BIT)
> +#define EPT_VIOLATION_WRITABLE		(1 << EPT_VIOLATION_WRITABLE_BIT)
> +#define EPT_VIOLATION_EXECUTABLE	(1 << EPT_VIOLATION_EXECUTABLE_BIT)
> +
> +/*
>   * VM-instruction error numbers
>   */
>  enum vm_instruction_error_number {
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index cf1b16d..859da8e 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -6170,14 +6170,18 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
>  	gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS);
>  	trace_kvm_page_fault(gpa, exit_qualification);
>  
> -	/* it is a read fault? */
> -	error_code = (exit_qualification << 2) & PFERR_USER_MASK;
> -	/* it is a write fault? */
> -	error_code |= exit_qualification & PFERR_WRITE_MASK;
> -	/* It is a fetch fault? */
> -	error_code |= (exit_qualification << 2) & PFERR_FETCH_MASK;
> -	/* ept page table is present? */
> -	error_code |= (exit_qualification & 0x38) != 0;
> +	/* Is it a read fault? */
> +	error_code = ((exit_qualification >> EPT_VIOLATION_READ_BIT) & 1)
> +		     << PFERR_USER_BIT;
> +	/* Is it a write fault? */
> +	error_code |= ((exit_qualification >> EPT_VIOLATION_WRITE_BIT) & 1)
> +		      << PFERR_WRITE_BIT;
> +	/* Is it a fetch fault? */
> +	error_code |= ((exit_qualification >> EPT_VIOLATION_INSTR_BIT) & 1)
> +		      << PFERR_FETCH_BIT;
> +	/* ept page table entry is present? */
> +	error_code |= ((exit_qualification >> EPT_VIOLATION_READABLE_BIT) & 1)

This last line is not enough now that nested VMX supports execute-only
pages.

Paolo

> +		      << PFERR_PRESENT_BIT;
>  
>  	vcpu->arch.exit_qualification = exit_qualification;
>  
>