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ANDROID: KVM: arm64: Refcount shadow structs on vcpu_{load/put}()

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Nothing currently prevents the host from tearing down a shadow VM while
a vCPU is loaded, which is likely to corrupt the hypervisor state. To
prevent this, refcount the shadow vm structs on vcpu_load() and
vcpu_put() and make sure to only allow tearing down a shadow VM when
it's refcount is 0.

Signed-off-by: Quentin Perret <qperret@google.com>
Bug: 209580772
Change-Id: I2860c3297516f8af6ff4a0d4c91127af4a34b62e
Signed-off-by: Will Deacon <willdeacon@google.com>
This commit is contained in:
Quentin Perret
2021-10-26 18:55:18 +01:00
committed by Will Deacon
parent dded44bcfd
commit 6f93dc7bb9
3 changed files with 42 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
arch/arm64/kvm/hyp/include/nvhe/pkvm.h
View File

@@ -53,7 +53,8 @@ extern struct kvm_shadow_vm **shadow_table;
int __pkvm_init_shadow(struct kvm *kvm, void *shadow_va, size_t size, void *pgd);
int __pkvm_teardown_shadow(struct kvm *kvm);
struct kvm_vcpu *hyp_get_shadow_vcpu(const struct kvm_vcpu *host_vcpu);
struct kvm_vcpu *get_shadow_vcpu(int shadow_handle, int vcpu_idx);
void put_shadow_vcpu(struct kvm_vcpu *vcpu);
u64 pvm_read_id_reg(const struct kvm_vcpu *vcpu, u32 id);
bool kvm_handle_pvm_sysreg(struct kvm_vcpu *vcpu, u64 *exit_code);

6
arch/arm64/kvm/hyp/nvhe/hyp-main.c
View File

@@ -501,6 +501,7 @@ static void handle___pkvm_vcpu_load(struct kvm_cpu_context *host_ctxt)
{
DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1);
struct pkvm_loaded_state *state;
int handle;
/* Why did you bother? */
if (!is_protected_kvm_enabled())
@@ -514,7 +515,8 @@ static void handle___pkvm_vcpu_load(struct kvm_cpu_context *host_ctxt)
vcpu = kern_hyp_va(vcpu);
state->vcpu = hyp_get_shadow_vcpu(vcpu) ?: vcpu;
handle = vcpu->arch.pkvm.shadow_handle;
state->vcpu = get_shadow_vcpu(handle, vcpu->vcpu_idx) ?: vcpu;
state->is_shadow = state->vcpu != vcpu;
if (state->is_shadow) {
@@ -540,6 +542,8 @@ static void handle___pkvm_vcpu_put(struct kvm_cpu_context *host_ctxt)
if (state->vcpu->arch.flags & KVM_ARM64_FP_ENABLED)
fpsimd_host_restore();
put_shadow_vcpu(state->vcpu);
/* "It's over and done with..." */
state->vcpu = NULL;
}

53
arch/arm64/kvm/hyp/nvhe/pkvm.c
View File

@@ -254,27 +254,30 @@ static struct kvm_shadow_vm *find_shadow_by_handle(int shadow_handle)
return shadow_table[shadow_index];
}
/*
* Returns the hyp shadow vcpu for the corresponding host vcpu,
* or NULL if it fails.
*/
struct kvm_vcpu *hyp_get_shadow_vcpu(const struct kvm_vcpu *vcpu)
struct kvm_vcpu *get_shadow_vcpu(int shadow_handle, int vcpu_idx)
{
struct shadow_vcpu_state *shadow_vcpu_state;
struct kvm_vcpu *vcpu = NULL;
struct kvm_shadow_vm *vm;
int vcpu_idx;
int shadow_handle;
shadow_handle = vcpu->arch.pkvm.shadow_handle;
hyp_spin_lock(&shadow_lock);
vm = find_shadow_by_handle(shadow_handle);
vcpu_idx = vcpu->vcpu_idx;
if (!vm || vcpu_idx < 0 || vm->created_vcpus <= vcpu_idx)
goto unlock;
vcpu = &vm->shadow_vcpus[vcpu_idx].vcpu;
hyp_page_ref_inc(hyp_virt_to_page(vm));
unlock:
hyp_spin_unlock(&shadow_lock);
if (unlikely(!vm || vcpu_idx < 0 || vcpu_idx >= vm->created_vcpus))
return NULL;
return vcpu;
}
shadow_vcpu_state = &vm->shadow_vcpus[vcpu_idx];
void put_shadow_vcpu(struct kvm_vcpu *vcpu)
{
struct kvm_shadow_vm *vm = vcpu->arch.pkvm.shadow_vm;
return &shadow_vcpu_state->vcpu;
hyp_spin_lock(&shadow_lock);
hyp_page_ref_dec(hyp_virt_to_page(vm));
hyp_spin_unlock(&shadow_lock);
}
/* Check and copy the supported features for the vcpu from the host. */
@@ -592,7 +595,7 @@ int __pkvm_teardown_shadow(struct kvm *kvm)
struct kvm_shadow_vm *vm;
struct kvm *host_kvm;
size_t shadow_size;
int shadow_handle;
int err, shadow_handle;
u64 pfn;
u64 nr_pages;
void *addr;
@@ -602,11 +605,20 @@ int __pkvm_teardown_shadow(struct kvm *kvm)
shadow_handle = kvm->arch.pkvm.shadow_handle;
/* Lookup then remove entry from the shadow table. */
hyp_spin_lock(&shadow_lock);
vm = find_shadow_by_handle(shadow_handle);
if (!vm)
return -ENOENT;
if (!vm) {
err = -ENOENT;
goto err_unlock;
}
shadow_size = vm->shadow_area_size;
if (WARN_ON(hyp_page_count(vm))) {
err = -EBUSY;
goto err_unlock;
}
__remove_shadow_table(shadow_handle);
hyp_spin_unlock(&shadow_lock);
/* Reclaim guest pages, and page-table pages */
mc = &vm->host_kvm->arch.pkvm.teardown_mc;
@@ -615,6 +627,7 @@ int __pkvm_teardown_shadow(struct kvm *kvm)
unpin_host_vcpus(vm);
/* Push the metadata pages to the teardown memcache */
shadow_size = vm->shadow_area_size;
host_kvm = vm->host_kvm;
memset(vm, 0, shadow_size);
for (addr = vm; addr < ((void *)vm + shadow_size); addr += PAGE_SIZE)
@@ -625,6 +638,10 @@ int __pkvm_teardown_shadow(struct kvm *kvm)
nr_pages = shadow_size >> PAGE_SHIFT;
WARN_ON(__pkvm_hyp_donate_host(pfn, nr_pages));
return 0;
err_unlock:
hyp_spin_unlock(&shadow_lock);
return err;
}
/*