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(-)

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;
-- 
2.31.1

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