Re: [PATCH v2 61/66] KVM: x86: Don't propagate MMU lpage support to memslot.disallow_lpage

Sean Christopherson
2020-03-03T16:00:58Z

On Tue, Mar 03, 2020 at 04:31:15PM +0100, Paolo Bonzini wrote:
> On 03/03/20 00:57, Sean Christopherson wrote:
> > Stop propagating MMU large page support into a memslot's disallow_lpage
> > now that the MMU's max_page_level handles the scenario where VMX's EPT is
> > enabled and EPT doesn't support 2M pages.
> >
> > No functional change intended.
> >
> > Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > ---
> > arch/x86/kvm/vmx/vmx.c | 3 ---
> > arch/x86/kvm/x86.c | 6 ++----
> > 2 files changed, 2 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index f8eb081b63fe..1fbe54dc3263 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -7698,9 +7698,6 @@ static __init int hardware_setup(void)
> > if (!cpu_has_vmx_tpr_shadow())
> > kvm_x86_ops->update_cr8_intercept = NULL;
> >
> > - if (enable_ept && !cpu_has_vmx_ept_2m_page())
> > - kvm_disable_largepages();
> > -
> > #if IS_ENABLED(CONFIG_HYPERV)
> > if (ms_hyperv.nested_features & HV_X64_NESTED_GUEST_MAPPING_FLUSH
> > && enable_ept) {
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 4fdf5b04f148..cc9b543d210b 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -9863,11 +9863,9 @@ static int kvm_alloc_memslot_metadata(struct kvm_memory_slot *slot,
> > ugfn = slot->userspace_addr >> PAGE_SHIFT;
> > /*
> > * If the gfn and userspace address are not aligned wrt each
> > - * other, or if explicitly asked to, disable large page
> > - * support for this slot
> > + * other, disable large page support for this slot.
> > */
> > - if ((slot->base_gfn ^ ugfn) & (KVM_PAGES_PER_HPAGE(level) - 1) ||
> > - !kvm_largepages_enabled()) {
> > + if ((slot->base_gfn ^ ugfn) & (KVM_PAGES_PER_HPAGE(level) - 1)) {
> > unsigned long j;
> >
> > for (j = 0; j < lpages; ++j)
> >
>
> This should technically go in the next patch.

Hmm, yeah, I agree. IIRC I split it this way so that the next patch didn't
touch any arch code, but removing only the call to kvm_disable_largepages()
would be cleaner.