On Wed, Feb 20, 2019 at 6:24 PM Sean Christopherson
<sean.j.christopherson@xxxxxxxxx> wrote:
>
> The memtype used by hardware when walking EPT tables is specified by
> software via an encoding in the EPTP. Ignoring the fact that no sane
> VMM would default to UC for page table walks, KVM only supports WB,
> and has only ever supported WB (added in commit ca72d970ff9a, "KVM:
> nEPT: Advertise WB type EPTP").
>
> Require WB and remove the UC handling altogether. Eliminating what is
> effectively dead code also removes the confusing error message (that
> never fires) regarding memtype, e.g. "EPT paging-structure memory type
> UC&WB are not supported" may be interpreted as stating that KVM unit
> tests require WC *and* WB.
>
> Cc: Marc Orr <marcorr@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
> x86/vmx_tests.c | 12 +++---------
> 1 file changed, 3 insertions(+), 9 deletions(-)
>
> diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
> index bd17088..c9cea0e 100644
> --- a/x86/vmx_tests.c
> +++ b/x86/vmx_tests.c
> @@ -1011,11 +1011,8 @@ static int setup_eptp(u64 hpa, bool enable_ad)
> printf("\tEPT is not supported");
> return 1;
> }
> -
> - if (!(ept_vpid.val & EPT_CAP_UC) &&
> - !(ept_vpid.val & EPT_CAP_WB)) {
> - printf("\tEPT paging-structure memory type "
> - "UC&WB are not supported\n");
> + if (!(ept_vpid.val & EPT_CAP_WB)) {
> + printf("WB memtype for EPT walks not supported\n");
> return 1;
> }
> if (!(ept_vpid.val & EPT_CAP_PWL4)) {
> @@ -1023,10 +1020,7 @@ static int setup_eptp(u64 hpa, bool enable_ad)
> return 1;
> }
>
> - if (ept_vpid.val & EPT_CAP_UC)
> - eptp = EPT_MEM_TYPE_UC;
> - else
> - eptp = EPT_MEM_TYPE_WB;
> + eptp = EPT_MEM_TYPE_WB;
> eptp |= (3 << EPTP_PG_WALK_LEN_SHIFT);
> eptp |= hpa;
> if (enable_ad)
> --
> 2.20.1
>
Reviewed-by: Marc Orr <marcorr@xxxxxxxxxx>
