Hello! I have tested this patch, it also fixes the crash on Exynos5410, and is indeed a better approach. Tested-by: Pavel Fedin <p.fedin@xxxxxxxxxxx> CC'ed general KVM mailing list too. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia > -----Original Message----- > From: kvmarm-bounces@xxxxxxxxxxxxxxxxxxxxx [mailto:kvmarm-bounces@xxxxxxxxxxxxxxxxxxxxx] On > Behalf Of Ard Biesheuvel > Sent: Friday, November 06, 2015 2:43 PM > To: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; kvmarm@xxxxxxxxxxxxxxxxxxxxx; marc.zyngier@xxxxxxx; > christoffer.dall@xxxxxxxxxx > Cc: Ard Biesheuvel > Subject: [PATCH] ARM/arm64: KVM: test properly for a PTE's uncachedness > > The open coded tests for checking whether a PTE maps a page as > uncached use a flawed 'pte_val(xxx) & CONST != CONST' pattern, > which is not guaranteed to work since the type of a mapping is an > index into the MAIR table, not a set of mutually exclusive bits. > > Considering that, on arm64, the S2 type definitions use the following > MAIR indexes > > #define MT_S2_NORMAL 0xf > #define MT_S2_DEVICE_nGnRE 0x1 > > we have been getting lucky merely because the S2 device mappings also > have the PTE_UXN bit set, which means that a device PTE still does not > equal a normal PTE after masking with the former type. > > Instead, implement proper checking against the MAIR indexes that are > known to define uncached memory attributes. > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > --- > arch/arm/include/asm/kvm_mmu.h | 11 +++++++++++ > arch/arm/kvm/mmu.c | 5 ++--- > arch/arm64/include/asm/kvm_mmu.h | 12 ++++++++++++ > 3 files changed, 25 insertions(+), 3 deletions(-) > > diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h > index 405aa1883307..422973835d41 100644 > --- a/arch/arm/include/asm/kvm_mmu.h > +++ b/arch/arm/include/asm/kvm_mmu.h > @@ -279,6 +279,17 @@ static inline void __kvm_extend_hypmap(pgd_t *boot_hyp_pgd, > pgd_t *merged_hyp_pgd, > unsigned long hyp_idmap_start) { } > > +static inline bool __kvm_pte_is_uncached(pte_t pte) > +{ > + switch (pte_val(pte) & L_PTE_MT_MASK) { > + case L_PTE_MT_UNCACHED: > + case L_PTE_MT_BUFFERABLE: > + case L_PTE_MT_DEV_SHARED: > + return true; > + } > + return false; > +} > + > #endif /* !__ASSEMBLY__ */ > > #endif /* __ARM_KVM_MMU_H__ */ > diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c > index 6984342da13d..eb9a06e3dbee 100644 > --- a/arch/arm/kvm/mmu.c > +++ b/arch/arm/kvm/mmu.c > @@ -213,7 +213,7 @@ static void unmap_ptes(struct kvm *kvm, pmd_t *pmd, > kvm_tlb_flush_vmid_ipa(kvm, addr); > > /* No need to invalidate the cache for device mappings */ > - if ((pte_val(old_pte) & PAGE_S2_DEVICE) != PAGE_S2_DEVICE) > + if (!__kvm_pte_is_uncached(old_pte)) > kvm_flush_dcache_pte(old_pte); > > put_page(virt_to_page(pte)); > @@ -305,8 +305,7 @@ static void stage2_flush_ptes(struct kvm *kvm, pmd_t *pmd, > > pte = pte_offset_kernel(pmd, addr); > do { > - if (!pte_none(*pte) && > - (pte_val(*pte) & PAGE_S2_DEVICE) != PAGE_S2_DEVICE) > + if (!pte_none(*pte) && !__kvm_pte_is_uncached(*pte)) > kvm_flush_dcache_pte(*pte); > } while (pte++, addr += PAGE_SIZE, addr != end); > } > diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h > index 61505676d085..5806f412a47a 100644 > --- a/arch/arm64/include/asm/kvm_mmu.h > +++ b/arch/arm64/include/asm/kvm_mmu.h > @@ -302,5 +302,17 @@ static inline void __kvm_extend_hypmap(pgd_t *boot_hyp_pgd, > merged_hyp_pgd[idmap_idx] = __pgd(__pa(boot_hyp_pgd) | PMD_TYPE_TABLE); > } > > +static inline bool __kvm_pte_is_uncached(pte_t pte) > +{ > + switch (pte_val(pte) & PTE_ATTRINDX_MASK) { > + case PTE_ATTRINDX(MT_DEVICE_nGnRnE): > + case PTE_ATTRINDX(MT_DEVICE_nGnRE): > + case PTE_ATTRINDX(MT_DEVICE_GRE): > + case PTE_ATTRINDX(MT_NORMAL_NC): > + return true; > + } > + return false; > +} > + > #endif /* __ASSEMBLY__ */ > #endif /* __ARM64_KVM_MMU_H__ */ > -- > 1.9.1 > > _______________________________________________ > kvmarm mailing list > kvmarm@xxxxxxxxxxxxxxxxxxxxx > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
