| Message ID | 20210123003003.3137525-1-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86/mmu: Use boolean returns for (S)PTE accessors | expand |
On 23/01/21 01:30, Sean Christopherson wrote: > Return a 'bool' instead of an 'int' for various PTE accessors that are > boolean in nature, e.g. is_shadow_present_pte(). Returning an int is > goofy and potentially dangerous, e.g. if a flag being checked is moved > into the upper 32 bits of a SPTE, then the compiler may silently squash > the entire check since casting to an int is guaranteed to yield a > return value of '0'. > > Opportunistically refactor is_last_spte() so that it naturally returns > a bool value instead of letting it implicitly cast 0/1 to false/true. > > No functional change intended. > > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/mmu.h | 2 +- > arch/x86/kvm/mmu/spte.h | 12 ++++-------- > 2 files changed, 5 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h > index 581925e476d6..f61e18dad2f3 100644 > --- a/arch/x86/kvm/mmu.h > +++ b/arch/x86/kvm/mmu.h > @@ -145,7 +145,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, > * > * TODO: introduce APIs to split these two cases. > */ > -static inline int is_writable_pte(unsigned long pte) > +static inline bool is_writable_pte(unsigned long pte) > { > return pte & PT_WRITABLE_MASK; > } > diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h > index 2b3a30bd38b0..398fd1bb13a7 100644 > --- a/arch/x86/kvm/mmu/spte.h > +++ b/arch/x86/kvm/mmu/spte.h > @@ -185,23 +185,19 @@ static inline bool is_access_track_spte(u64 spte) > return !spte_ad_enabled(spte) && (spte & shadow_acc_track_mask) == 0; > } > > -static inline int is_shadow_present_pte(u64 pte) > +static inline bool is_shadow_present_pte(u64 pte) > { > return (pte != 0) && !is_mmio_spte(pte); > } > > -static inline int is_large_pte(u64 pte) > +static inline bool is_large_pte(u64 pte) > { > return pte & PT_PAGE_SIZE_MASK; > } > > -static inline int is_last_spte(u64 pte, int level) > +static inline bool is_last_spte(u64 pte, int level) > { > - if (level == PG_LEVEL_4K) > - return 1; > - if (is_large_pte(pte)) > - return 1; > - return 0; > + return (level == PG_LEVEL_4K) || is_large_pte(pte); > } > > static inline bool is_executable_pte(u64 spte) > Queued, thanks. Paolo
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index 581925e476d6..f61e18dad2f3 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -145,7 +145,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, * * TODO: introduce APIs to split these two cases. */ -static inline int is_writable_pte(unsigned long pte) +static inline bool is_writable_pte(unsigned long pte) { return pte & PT_WRITABLE_MASK; } diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h index 2b3a30bd38b0..398fd1bb13a7 100644 --- a/arch/x86/kvm/mmu/spte.h +++ b/arch/x86/kvm/mmu/spte.h @@ -185,23 +185,19 @@ static inline bool is_access_track_spte(u64 spte) return !spte_ad_enabled(spte) && (spte & shadow_acc_track_mask) == 0; } -static inline int is_shadow_present_pte(u64 pte) +static inline bool is_shadow_present_pte(u64 pte) { return (pte != 0) && !is_mmio_spte(pte); } -static inline int is_large_pte(u64 pte) +static inline bool is_large_pte(u64 pte) { return pte & PT_PAGE_SIZE_MASK; } -static inline int is_last_spte(u64 pte, int level) +static inline bool is_last_spte(u64 pte, int level) { - if (level == PG_LEVEL_4K) - return 1; - if (is_large_pte(pte)) - return 1; - return 0; + return (level == PG_LEVEL_4K) || is_large_pte(pte); } static inline bool is_executable_pte(u64 spte)
Return a 'bool' instead of an 'int' for various PTE accessors that are boolean in nature, e.g. is_shadow_present_pte(). Returning an int is goofy and potentially dangerous, e.g. if a flag being checked is moved into the upper 32 bits of a SPTE, then the compiler may silently squash the entire check since casting to an int is guaranteed to yield a return value of '0'. Opportunistically refactor is_last_spte() so that it naturally returns a bool value instead of letting it implicitly cast 0/1 to false/true. No functional change intended. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/mmu.h | 2 +- arch/x86/kvm/mmu/spte.h | 12 ++++-------- 2 files changed, 5 insertions(+), 9 deletions(-)