[V2 09/11] KVM: selftests: Make ucall work with encrypted guests

Peter Gonda
2022-08-01T20:12:26Z

Add support for encrypted, SEV, guests in the ucall framework. If
encryption is enabled set up a pool of ucall structs in the guests'
shared memory region. This was suggested in the thread on "[RFC PATCH
00/10] KVM: selftests: Add support for test-selectable ucall
implementations". Using a listed as suggested there doesn't work well
because the list is setup using HVAs not GVAs so use a bitmap + array
solution instead to get the same pool result.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Gonda <pgonda@google.com>
---
.../selftests/kvm/include/kvm_util_base.h | 3 +
.../selftests/kvm/include/ucall_common.h | 14 +--
.../testing/selftests/kvm/lib/ucall_common.c | 112 +++++++++++++++++-
3 files changed, 115 insertions(+), 14 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 8ce9e5be70a3..ad4abc6be1ab 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -102,6 +102,9 @@ struct kvm_vm {
int stats_fd;
struct kvm_stats_header stats_header;
struct kvm_stats_desc *stats_desc;
+
+ bool use_ucall_list;
+ struct list_head ucall_list;
};

diff --git a/tools/testing/selftests/kvm/include/ucall_common.h b/tools/testing/selftests/kvm/include/ucall_common.h
index c1bc8e33ef3f..a96220ac6024 100644
--- a/tools/testing/selftests/kvm/include/ucall_common.h
+++ b/tools/testing/selftests/kvm/include/ucall_common.h
@@ -22,6 +22,10 @@ enum {
struct ucall {
uint64_t cmd;
uint64_t args[UCALL_MAX_ARGS];
+
+ /* For encrypted guests. */
+ uint64_t idx;
+ struct ucall *hva;
};

void ucall_arch_init(struct kvm_vm *vm, void *arg);
@@ -32,15 +36,9 @@ uint64_t ucall_arch_get_ucall(struct kvm_vcpu *vcpu);
void ucall(uint64_t cmd, int nargs, ...);
uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc);

-static inline void ucall_init(struct kvm_vm *vm, void *arg)
-{
- ucall_arch_init(vm, arg);
-}
+void ucall_init(struct kvm_vm *vm, void *arg);

-static inline void ucall_uninit(struct kvm_vm *vm)
-{
- ucall_arch_uninit(vm);
-}
+void ucall_uninit(struct kvm_vm *vm);

#define GUEST_SYNC_ARGS(stage, arg1, arg2, arg3, arg4) \
ucall(UCALL_SYNC, 6, "hello", stage, arg1, arg2, arg3, arg4)
diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c
index a060252bab40..feb0173179ec 100644
--- a/tools/testing/selftests/kvm/lib/ucall_common.c
+++ b/tools/testing/selftests/kvm/lib/ucall_common.c
@@ -1,22 +1,122 @@
// SPDX-License-Identifier: GPL-2.0-only
#include "kvm_util.h"
+#include "linux/types.h"
+#include "linux/bitmap.h"
+#include "linux/atomic.h"
+
+struct ucall_header {
+ DECLARE_BITMAP(in_use, KVM_MAX_VCPUS);
+ struct ucall ucalls[KVM_MAX_VCPUS];
+};
+
+static bool use_ucall_list;
+static struct ucall_header *ucall_hdr;
+
+void ucall_init(struct kvm_vm *vm, void *arg)
+{
+ struct ucall *uc;
+ struct ucall_header *hdr;
+ vm_vaddr_t vaddr;
+ int i;
+
+ use_ucall_list = vm->use_ucall_list;
+ sync_global_to_guest(vm, use_ucall_list);
+ if (!use_ucall_list)
+ goto out;
+
+ TEST_ASSERT(!ucall_hdr,
+ "Only a single encrypted guest at a time for ucalls.");
+ vaddr = vm_vaddr_alloc_shared(vm, sizeof(*hdr), vm->page_size);
+ hdr = (struct ucall_header *)addr_gva2hva(vm, vaddr);
+ memset(hdr, 0, sizeof(*hdr));
+
+ for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+ uc = &hdr->ucalls[i];
+ uc->hva = uc;
+ uc->idx = i;
+ }
+
+ ucall_hdr = (struct ucall_header *)vaddr;
+ sync_global_to_guest(vm, ucall_hdr);
+
+out:
+ ucall_arch_init(vm, arg);
+}
+
+void ucall_uninit(struct kvm_vm *vm)
+{
+ use_ucall_list = false;
+ ucall_hdr = NULL;
+
+ ucall_arch_uninit(vm);
+}
+
+static struct ucall *ucall_alloc(void)
+{
+ struct ucall *uc = NULL;
+ int i;
+
+ if (!use_ucall_list)
+ goto out;
+
+ for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+ if (atomic_test_and_set_bit(i, ucall_hdr->in_use))
+ continue;
+
+ uc = &ucall_hdr->ucalls[i];
+ }
+
+out:
+ return uc;
+}
+
+static void ucall_free(struct ucall *uc)
+{
+ if (!use_ucall_list)
+ return;
+
+ clear_bit(uc->idx, ucall_hdr->in_use);
+}
+
+static vm_vaddr_t get_ucall_addr(struct ucall *uc)
+{
+ if (use_ucall_list)
+ return (vm_vaddr_t)uc->hva;
+
+ return (vm_vaddr_t)uc;
+}

void ucall(uint64_t cmd, int nargs, ...)
{
- struct ucall uc = {
- .cmd = cmd,
- };
+ struct ucall *uc;
+ struct ucall tmp;
va_list va;
int i;

+ uc = ucall_alloc();
+ if (!uc)
+ uc = &tmp;
+
+ uc->cmd = cmd;
+
nargs = min(nargs, UCALL_MAX_ARGS);

va_start(va, nargs);
for (i = 0; i < nargs; ++i)
- uc.args[i] = va_arg(va, uint64_t);
+ uc->args[i] = va_arg(va, uint64_t);
va_end(va);

- ucall_arch_do_ucall((vm_vaddr_t)&uc);
+ ucall_arch_do_ucall(get_ucall_addr(uc));
+
+ ucall_free(uc);
+}
+
+static void *get_ucall_hva(struct kvm_vm *vm, uint64_t uc)
+{
+ if (vm->use_ucall_list)
+ return (void *)uc;
+
+ return addr_gva2hva(vm, uc);
}

uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
@@ -27,7 +127,7 @@ uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
if (!uc)
uc = &ucall;

- addr = addr_gva2hva(vcpu->vm, ucall_arch_get_ucall(vcpu));
+ addr = get_ucall_hva(vcpu->vm, ucall_arch_get_ucall(vcpu));
if (addr) {
memcpy(uc, addr, sizeof(*uc));
vcpu_run_complete_io(vcpu);
--
2.37.1.455.g008518b4e5-goog