Re: [PATCH 4.19 STABLE] KVM: x86: introduce is_pae_paging

[Sasha Levin]

On Tue, Nov 12, 2019 at 12:05:44AM +0100, Paolo Bonzini wrote:
> On 11/11/19 23:54, Sean Christopherson wrote:
> > From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> >
> > Upstream commit bf03d4f9334728bf7c8ffc7de787df48abd6340e.
> >
> > Checking for 32-bit PAE is quite common around code that fiddles with
> > the PDPTRs.  Add a function to compress all checks into a single
> > invocation.
> >
> > Moving to the common helper also fixes a subtle bug in kvm_set_cr3()
> > where it fails to check is_long_mode() and results in KVM incorrectly
> > attempting to load PDPTRs for a 64-bit guest.
> >
> > Reviewed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > [sean: backport to 4.x; handle vmx.c split in 5.x, call out the bugfix]
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > ---
> >  arch/x86/kvm/vmx.c | 7 +++----
> >  arch/x86/kvm/x86.c | 8 ++++----
> >  arch/x86/kvm/x86.h | 5 +++++
> >  3 files changed, 12 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index 6f7b3acdab26..83acaed244ba 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -5181,7 +5181,7 @@ static void ept_load_pdptrs(struct kvm_vcpu *vcpu)
> >  		      (unsigned long *)&vcpu->arch.regs_dirty))
> >  		return;
> >
> > -	if (is_paging(vcpu) && is_pae(vcpu) && !is_long_mode(vcpu)) {
> > +	if (is_pae_paging(vcpu)) {
> >  		vmcs_write64(GUEST_PDPTR0, mmu->pdptrs[0]);
> >  		vmcs_write64(GUEST_PDPTR1, mmu->pdptrs[1]);
> >  		vmcs_write64(GUEST_PDPTR2, mmu->pdptrs[2]);
> > @@ -5193,7 +5193,7 @@ static void ept_save_pdptrs(struct kvm_vcpu *vcpu)
> >  {
> >  	struct kvm_mmu *mmu = vcpu->arch.walk_mmu;
> >
> > -	if (is_paging(vcpu) && is_pae(vcpu) && !is_long_mode(vcpu)) {
> > +	if (is_pae_paging(vcpu)) {
> >  		mmu->pdptrs[0] = vmcs_read64(GUEST_PDPTR0);
> >  		mmu->pdptrs[1] = vmcs_read64(GUEST_PDPTR1);
> >  		mmu->pdptrs[2] = vmcs_read64(GUEST_PDPTR2);
> > @@ -12021,8 +12021,7 @@ static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool ne
> >  		 * If PAE paging and EPT are both on, CR3 is not used by the CPU and
> >  		 * must not be dereferenced.
> >  		 */
> > -		if (!is_long_mode(vcpu) && is_pae(vcpu) && is_paging(vcpu) &&
> > -		    !nested_ept) {
> > +		if (is_pae_paging(vcpu) && !nested_ept) {
> >  			if (!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3)) {
> >  				*entry_failure_code = ENTRY_FAIL_PDPTE;
> >  				return 1;
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 6ae8a013af31..b9b87fb75ac0 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -633,7 +633,7 @@ bool pdptrs_changed(struct kvm_vcpu *vcpu)
> >  	gfn_t gfn;
> >  	int r;
> >
> > -	if (is_long_mode(vcpu) || !is_pae(vcpu) || !is_paging(vcpu))
> > +	if (!is_pae_paging(vcpu))
> >  		return false;
> >
> >  	if (!test_bit(VCPU_EXREG_PDPTR,
> > @@ -884,8 +884,8 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
> >  	if (is_long_mode(vcpu) &&
> >  	    (cr3 & rsvd_bits(cpuid_maxphyaddr(vcpu), 63)))
> >  		return 1;
> > -	else if (is_pae(vcpu) && is_paging(vcpu) &&
> > -		   !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
> > +	else if (is_pae_paging(vcpu) &&
> > +		 !load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))
> >  		return 1;
> >
> >  	kvm_mmu_new_cr3(vcpu, cr3, skip_tlb_flush);
> > @@ -8312,7 +8312,7 @@ static int __set_sregs(struct kvm_vcpu *vcpu, struct kvm_sregs *sregs)
> >  		kvm_update_cpuid(vcpu);
> >
> >  	idx = srcu_read_lock(&vcpu->kvm->srcu);
> > -	if (!is_long_mode(vcpu) && is_pae(vcpu) && is_paging(vcpu)) {
> > +	if (is_pae_paging(vcpu)) {
> >  		load_pdptrs(vcpu, vcpu->arch.walk_mmu, kvm_read_cr3(vcpu));
> >  		mmu_reset_needed = 1;
> >  	}
> > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> > index 3a91ea760f07..608e5f8c5d0a 100644
> > --- a/arch/x86/kvm/x86.h
> > +++ b/arch/x86/kvm/x86.h
> > @@ -139,6 +139,11 @@ static inline int is_paging(struct kvm_vcpu *vcpu)
> >  	return likely(kvm_read_cr0_bits(vcpu, X86_CR0_PG));
> >  }
> >
> > +static inline bool is_pae_paging(struct kvm_vcpu *vcpu)
> > +{
> > +	return !is_long_mode(vcpu) && is_pae(vcpu) && is_paging(vcpu);
> > +}
> > +
> >  static inline u32 bit(int bitno)
> >  {
> >  	return 1 << (bitno & 31);
>
> Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Queued up for 4.19, thank you.

--
Thanks,
Sasha