On Fri, Dec 10, 2021, Lai Jiangshan wrote: > From: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx> > > If root_level >= 4, shadow_root_level must be >= 4 too. Please explain why so that it's explicitly clear why this ok, e.g. Drop the shadow_root_level check when determining if a "fast" PGD switch is allowed, as KVM never shadows 64-bit guest pages tables with PAE paging (32-bit KVM doesn't support 64-bit guests). with that: Reviewed-by: Sean Christopherson <seanjc@xxxxxxxxxx> > Checking only root_level can reduce a check. > > Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx> > --- > arch/x86/kvm/mmu/mmu.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 11b06d536cc9..846a2e426e0b 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -4136,8 +4136,7 @@ static bool fast_pgd_switch(struct kvm_vcpu *vcpu, gpa_t new_pgd, > * having to deal with PDPTEs. We may add support for 32-bit hosts/VMs > * later if necessary. > */ > - if (mmu->shadow_root_level >= PT64_ROOT_4LEVEL && > - mmu->root_level >= PT64_ROOT_4LEVEL) > + if (mmu->root_level >= PT64_ROOT_4LEVEL) > return cached_root_available(vcpu, new_pgd, new_role); > > return false; > -- > 2.19.1.6.gb485710b >
