arm/arm64: KVM: Introduce stage2_unmap_vm

commit 957db105c99792ae8ef61ffc9ae77d910f6471da upstream.

Introduce a new function to unmap user RAM regions in the stage2 page
tables.  This is needed on reboot (or when the guest turns off the MMU)
to ensure we fault in pages again and make the dcache, RAM, and icache
coherent.

Using unmap_stage2_range for the whole guest physical range does not
work, because that unmaps IO regions (such as the GIC) which will not be
recreated or in the best case faulted in on a page-by-page basis.

Call this function on secondary and subsequent calls to the
KVM_ARM_VCPU_INIT ioctl so that a reset VCPU will detect the guest
Stage-1 MMU is off when faulting in pages and make the caches coherent.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 3f688b458143503f3f369a2c89d3f2eabd3b0934..c02a8367dee44f601fb8cdee9758e17a4a119084 100644 (file)
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -47,6 +47,7 @@ int create_hyp_io_mappings(void *from, void *to, phys_addr_t);
 void free_boot_hyp_pgd(void);
 void free_hyp_pgds(void);
 
+void stage2_unmap_vm(struct kvm *kvm);
 int kvm_alloc_stage2_pgd(struct kvm *kvm);
 void kvm_free_stage2_pgd(struct kvm *kvm);
 int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index e2ae91dbde84370b30141cd8489c56d4e50738c1..0fb257c84366df3dbcbee7152bcdf8e7fd5b76ac 100644 (file)
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -676,6 +676,13 @@ static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
        if (ret)
                return ret;
 
+       /*
+        * Ensure a rebooted VM will fault in RAM pages and detect if the
+        * guest MMU is turned off and flush the caches as needed.
+        */
+       if (vcpu->arch.has_run_once)
+               stage2_unmap_vm(vcpu->kvm);
+
        vcpu_reset_hcr(vcpu);
 
        /*

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 8cfb491776a94fd942f69d11162944b60ee85864..bbf6a127ef3c13665423ecf6c8e5460c4392d207 100644 (file)
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -556,6 +556,71 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
        unmap_range(kvm, kvm->arch.pgd, start, size);
 }
 
+static void stage2_unmap_memslot(struct kvm *kvm,
+                                struct kvm_memory_slot *memslot)
+{
+       hva_t hva = memslot->userspace_addr;
+       phys_addr_t addr = memslot->base_gfn << PAGE_SHIFT;
+       phys_addr_t size = PAGE_SIZE * memslot->npages;
+       hva_t reg_end = hva + size;
+
+       /*
+        * A memory region could potentially cover multiple VMAs, and any holes
+        * between them, so iterate over all of them to find out if we should
+        * unmap any of them.
+        *
+        *     +--------------------------------------------+
+        * +---------------+----------------+   +----------------+
+        * |   : VMA 1     |      VMA 2     |   |    VMA 3  :    |
+        * +---------------+----------------+   +----------------+
+        *     |               memory region                |
+        *     +--------------------------------------------+
+        */
+       do {
+               struct vm_area_struct *vma = find_vma(current->mm, hva);
+               hva_t vm_start, vm_end;
+
+               if (!vma || vma->vm_start >= reg_end)
+                       break;
+
+               /*
+                * Take the intersection of this VMA with the memory region
+                */
+               vm_start = max(hva, vma->vm_start);
+               vm_end = min(reg_end, vma->vm_end);
+
+               if (!(vma->vm_flags & VM_PFNMAP)) {
+                       gpa_t gpa = addr + (vm_start - memslot->userspace_addr);
+                       unmap_stage2_range(kvm, gpa, vm_end - vm_start);
+               }
+               hva = vm_end;
+       } while (hva < reg_end);
+}
+
+/**
+ * stage2_unmap_vm - Unmap Stage-2 RAM mappings
+ * @kvm: The struct kvm pointer
+ *
+ * Go through the memregions and unmap any reguler RAM
+ * backing memory already mapped to the VM.
+ */
+void stage2_unmap_vm(struct kvm *kvm)
+{
+       struct kvm_memslots *slots;
+       struct kvm_memory_slot *memslot;
+       int idx;
+
+       idx = srcu_read_lock(&kvm->srcu);
+       spin_lock(&kvm->mmu_lock);
+
+       slots = kvm_memslots(kvm);
+       kvm_for_each_memslot(memslot, slots)
+               stage2_unmap_memslot(kvm, memslot);
+
+       spin_unlock(&kvm->mmu_lock);
+       srcu_read_unlock(&kvm->srcu, idx);
+}
+
 /**
  * kvm_free_stage2_pgd - free all stage-2 tables
  * @kvm:       The KVM struct pointer for the VM.

diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index a030d163840bf02e9eccd4828f54743dc4b8363b..0d51874c838f42c7afdab5485d3c1a094ef69049 100644 (file)
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -74,6 +74,7 @@ int create_hyp_io_mappings(void *from, void *to, phys_addr_t);
 void free_boot_hyp_pgd(void);
 void free_hyp_pgds(void);
 
+void stage2_unmap_vm(struct kvm *kvm);
 int kvm_alloc_stage2_pgd(struct kvm *kvm);
 void kvm_free_stage2_pgd(struct kvm *kvm);
 int kvm_phys_addr_ioremap(struct kvm *kvm, phys_addr_t guest_ipa,