From 849260c72c6b8bd53850cb00b80027db3a273c2c Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Mon, 17 Nov 2014 14:58:53 +0000 Subject: arm, arm64: KVM: handle potential incoherency of readonly memslots Readonly memslots are often used to implement emulation of ROMs and NOR flashes, in which case the guest may legally map these regions as uncached. To deal with the incoherency associated with uncached guest mappings, treat all readonly memslots as incoherent, and ensure that pages that belong to regions tagged as such are flushed to DRAM before being passed to the guest. Signed-off-by: Ard Biesheuvel Signed-off-by: Marc Zyngier --- arch/arm/kvm/mmu.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c index cb924c6d56a..f2a9874ff5c 100644 --- a/arch/arm/kvm/mmu.c +++ b/arch/arm/kvm/mmu.c @@ -919,7 +919,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, if (!hugetlb && !force_pte) hugetlb = transparent_hugepage_adjust(&pfn, &fault_ipa); - fault_ipa_uncached = false; + fault_ipa_uncached = memslot->flags & KVM_MEMSLOT_INCOHERENT; if (hugetlb) { pmd_t new_pmd = pfn_pmd(pfn, mem_type); @@ -1298,11 +1298,12 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, hva = vm_end; } while (hva < reg_end); - if (ret) { - spin_lock(&kvm->mmu_lock); + spin_lock(&kvm->mmu_lock); + if (ret) unmap_stage2_range(kvm, mem->guest_phys_addr, mem->memory_size); - spin_unlock(&kvm->mmu_lock); - } + else + stage2_flush_memslot(kvm, memslot); + spin_unlock(&kvm->mmu_lock); return ret; } @@ -1314,6 +1315,15 @@ void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free, int kvm_arch_create_memslot(struct kvm *kvm, struct kvm_memory_slot *slot, unsigned long npages) { + /* + * Readonly memslots are not incoherent with the caches by definition, + * but in practice, they are used mostly to emulate ROMs or NOR flashes + * that the guest may consider devices and hence map as uncached. + * To prevent incoherency issues in these cases, tag all readonly + * regions as incoherent. + */ + if (slot->flags & KVM_MEM_READONLY) + slot->flags |= KVM_MEMSLOT_INCOHERENT; return 0; } -- cgit v1.2.3-70-g09d2