diff options
| -rw-r--r-- | arch/arm64/include/asm/kvm_mmu.h | 18 | ||||
| -rw-r--r-- | arch/arm64/kvm/mmu.c | 59 |
2 files changed, 55 insertions, 22 deletions
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index b98ac6aa631f..ae563ebd6aee 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -371,6 +371,24 @@ static inline void kvm_fault_unlock(struct kvm *kvm) read_unlock(&kvm->mmu_lock); } +/* + * ARM64 KVM relies on a simple conversion from physaddr to a kernel + * virtual address (KVA) when it does cache maintenance as the CMO + * instructions work on virtual addresses. This is incompatible with + * VM_PFNMAP VMAs which may not have a kernel direct mapping to a + * virtual address. + * + * With S2FWB and CACHE DIC features, KVM need not do cache flushing + * and CMOs are NOP'd. This has the effect of no longer requiring a + * KVA for addresses mapped into the S2. The presence of these features + * are thus necessary to support cacheable S2 mapping of VM_PFNMAP. + */ +static inline bool kvm_supports_cacheable_pfnmap(void) +{ + return cpus_have_final_cap(ARM64_HAS_STAGE2_FWB) && + cpus_have_final_cap(ARM64_HAS_CACHE_DIC); +} + #ifdef CONFIG_PTDUMP_STAGE2_DEBUGFS void kvm_s2_ptdump_create_debugfs(struct kvm *kvm); #else diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 708a635e38bc..3a9e2248f82d 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1654,18 +1654,39 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, if (is_error_noslot_pfn(pfn)) return -EFAULT; + /* + * Check if this is non-struct page memory PFN, and cannot support + * CMOs. It could potentially be unsafe to access as cachable. + */ if (vm_flags & (VM_PFNMAP | VM_MIXEDMAP) && !pfn_is_map_memory(pfn)) { - /* - * If the page was identified as device early by looking at - * the VMA flags, vma_pagesize is already representing the - * largest quantity we can map. If instead it was mapped - * via __kvm_faultin_pfn(), vma_pagesize is set to PAGE_SIZE - * and must not be upgraded. - * - * In both cases, we don't let transparent_hugepage_adjust() - * change things at the last minute. - */ - s2_force_noncacheable = true; + if (is_vma_cacheable) { + /* + * Whilst the VMA owner expects cacheable mapping to this + * PFN, hardware also has to support the FWB and CACHE DIC + * features. + * + * ARM64 KVM relies on kernel VA mapping to the PFN to + * perform cache maintenance as the CMO instructions work on + * virtual addresses. VM_PFNMAP region are not necessarily + * mapped to a KVA and hence the presence of hardware features + * S2FWB and CACHE DIC are mandatory to avoid the need for + * cache maintenance. + */ + if (!kvm_supports_cacheable_pfnmap()) + return -EFAULT; + } else { + /* + * If the page was identified as device early by looking at + * the VMA flags, vma_pagesize is already representing the + * largest quantity we can map. If instead it was mapped + * via __kvm_faultin_pfn(), vma_pagesize is set to PAGE_SIZE + * and must not be upgraded. + * + * In both cases, we don't let transparent_hugepage_adjust() + * change things at the last minute. + */ + s2_force_noncacheable = true; + } } else if (logging_active && !write_fault) { /* * Only actually map the page as writable if this was a write @@ -1674,15 +1695,6 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, writable = false; } - /* - * Prevent non-cacheable mappings in the stage-2 if a region of memory - * is cacheable in the primary MMU and the kernel lacks a cacheable - * alias. KVM cannot guarantee coherency between the guest/host aliases - * without the ability to perform CMOs. - */ - if (is_vma_cacheable && s2_force_noncacheable) - return -EINVAL; - if (exec_fault && s2_force_noncacheable) return -ENOEXEC; @@ -2243,8 +2255,11 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, break; } - /* Cacheable PFNMAP is not allowed */ - if (kvm_vma_is_cacheable(vma)) { + /* + * Cacheable PFNMAP is allowed only if the hardware + * supports it. + */ + if (kvm_vma_is_cacheable(vma) && !kvm_supports_cacheable_pfnmap()) { ret = -EINVAL; break; } |