| Message ID | 20220221162243.683208-12-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM MMU refactoring part 2: role changes | expand |
On Mon, Feb 21, 2022, Paolo Bonzini wrote: > kvm_calc_shadow_root_page_role_common is the same as > kvm_calc_cpu_mode except for the level, which is overwritten > afterwards in kvm_calc_shadow_mmu_root_page_role > and kvm_calc_shadow_npt_root_page_role. > > role.base.direct is already set correctly for the CPU mode, > and CR0.PG=1 is required for VMRUN so it will also be > correct for nested NPT. Bzzzt, this is wrong, the nested NPT MMU is indirect but will be computed as direct. > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > arch/x86/kvm/mmu/mmu.c | 21 ++------------------- > 1 file changed, 2 insertions(+), 19 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 3ffa6f2bf991..31874fad12fb 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -4796,27 +4796,11 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu, > reset_tdp_shadow_zero_bits_mask(context); > } > > -static union kvm_mmu_role > -kvm_calc_shadow_root_page_role_common(struct kvm_vcpu *vcpu, > - const struct kvm_mmu_role_regs *regs) > -{ > - union kvm_mmu_role role = kvm_calc_mmu_role_common(vcpu, regs); > - > - role.base.smep_andnot_wp = role.ext.cr4_smep && !____is_cr0_wp(regs); > - role.base.smap_andnot_wp = role.ext.cr4_smap && !____is_cr0_wp(regs); > - role.base.has_4_byte_gpte = ____is_cr0_pg(regs) && !____is_cr4_pae(regs); > - > - return role; > -} > - > static union kvm_mmu_role > kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu, > const struct kvm_mmu_role_regs *regs) > { > - union kvm_mmu_role role = > - kvm_calc_shadow_root_page_role_common(vcpu, regs); > - > - role.base.direct = !____is_cr0_pg(regs); > + union kvm_mmu_role role = kvm_calc_cpu_mode(vcpu, regs); > > if (!____is_efer_lma(regs)) > role.base.level = PT32E_ROOT_LEVEL; > @@ -4869,9 +4853,8 @@ kvm_calc_shadow_npt_root_page_role(struct kvm_vcpu *vcpu, > const struct kvm_mmu_role_regs *regs) > { > union kvm_mmu_role role = > - kvm_calc_shadow_root_page_role_common(vcpu, regs); > + kvm_calc_cpu_mode(vcpu, regs); No need to split this line with the less verbose name. > > - role.base.direct = false; As above, this line needs to stay. > role.base.level = kvm_mmu_get_tdp_level(vcpu); > > return role; > -- > 2.31.1 > >
On 3/8/22 18:48, Sean Christopherson wrote: > On Mon, Feb 21, 2022, Paolo Bonzini wrote: >> kvm_calc_shadow_root_page_role_common is the same as >> kvm_calc_cpu_mode except for the level, which is overwritten >> afterwards in kvm_calc_shadow_mmu_root_page_role >> and kvm_calc_shadow_npt_root_page_role. >> >> role.base.direct is already set correctly for the CPU mode, >> and CR0.PG=1 is required for VMRUN so it will also be >> correct for nested NPT. > > Bzzzt, this is wrong, the nested NPT MMU is indirect but will be computed as direct. CR0.PG=1 means it's *not* direct: > + role.base.direct = !____is_cr0_pg(regs); Paolo
On Tue, Mar 08, 2022, Paolo Bonzini wrote: > On 3/8/22 18:48, Sean Christopherson wrote: > > On Mon, Feb 21, 2022, Paolo Bonzini wrote: > > > kvm_calc_shadow_root_page_role_common is the same as > > > kvm_calc_cpu_mode except for the level, which is overwritten > > > afterwards in kvm_calc_shadow_mmu_root_page_role > > > and kvm_calc_shadow_npt_root_page_role. > > > > > > role.base.direct is already set correctly for the CPU mode, > > > and CR0.PG=1 is required for VMRUN so it will also be > > > correct for nested NPT. > > > > Bzzzt, this is wrong, the nested NPT MMU is indirect but will be computed as direct. > > CR0.PG=1 means it's *not* direct: > > > + role.base.direct = !____is_cr0_pg(regs); Ha! I was just cleverly making the case for checking ____is_cr0_pg() instead of "direct" for computing the dependent flags, I swear... On a serious note, can we add a WARN_ON_ONCE(role.base.direct)? Not so much that the WARN will be helpful, but to document the subtle dependency? If the relevant code goes away in the end, ignore this requrest.
On 3/8/22 19:17, Sean Christopherson wrote: >>> + role.base.direct = !____is_cr0_pg(regs); > > On a serious note, can we add a WARN_ON_ONCE(role.base.direct)? Not so much that > the WARN will be helpful, but to document the subtle dependency? If the relevant > code goes away in the end, ignore this requrest. Ok, that can be done. Either that or !is_cr0_pg(). Paolo
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 3ffa6f2bf991..31874fad12fb 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4796,27 +4796,11 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu, reset_tdp_shadow_zero_bits_mask(context); } -static union kvm_mmu_role -kvm_calc_shadow_root_page_role_common(struct kvm_vcpu *vcpu, - const struct kvm_mmu_role_regs *regs) -{ - union kvm_mmu_role role = kvm_calc_mmu_role_common(vcpu, regs); - - role.base.smep_andnot_wp = role.ext.cr4_smep && !____is_cr0_wp(regs); - role.base.smap_andnot_wp = role.ext.cr4_smap && !____is_cr0_wp(regs); - role.base.has_4_byte_gpte = ____is_cr0_pg(regs) && !____is_cr4_pae(regs); - - return role; -} - static union kvm_mmu_role kvm_calc_shadow_mmu_root_page_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs) { - union kvm_mmu_role role = - kvm_calc_shadow_root_page_role_common(vcpu, regs); - - role.base.direct = !____is_cr0_pg(regs); + union kvm_mmu_role role = kvm_calc_cpu_mode(vcpu, regs); if (!____is_efer_lma(regs)) role.base.level = PT32E_ROOT_LEVEL; @@ -4869,9 +4853,8 @@ kvm_calc_shadow_npt_root_page_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs) { union kvm_mmu_role role = - kvm_calc_shadow_root_page_role_common(vcpu, regs); + kvm_calc_cpu_mode(vcpu, regs); - role.base.direct = false; role.base.level = kvm_mmu_get_tdp_level(vcpu); return role;
kvm_calc_shadow_root_page_role_common is the same as kvm_calc_cpu_mode except for the level, which is overwritten afterwards in kvm_calc_shadow_mmu_root_page_role and kvm_calc_shadow_npt_root_page_role. role.base.direct is already set correctly for the CPU mode, and CR0.PG=1 is required for VMRUN so it will also be correct for nested NPT. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> --- arch/x86/kvm/mmu/mmu.c | 21 ++------------------- 1 file changed, 2 insertions(+), 19 deletions(-)