Re: [RFC 06/16] KVM: selftests: add library for creating/interacting with SEV guests

[Krish Sadhukhan <krish.sadhukhan@oracle.com>]

On 10/6/21 1:37 PM, Michael Roth wrote:
> Add interfaces to allow tests to create/manage SEV guests. The
> additional state associated with these guests is encapsulated in a new
> struct sev_vm, which is a light wrapper around struct kvm_vm. These
> VMs will use vm_set_memory_encryption() and vm_get_encrypted_phy_pages()
> under the covers to configure and sync up with the core kvm_util
> library on what should/shouldn't be treated as encrypted memory.
>
> Signed-off-by: Michael Roth <michael.roth@amd.com>
> ---
>   tools/testing/selftests/kvm/Makefile          |   1 +
>   .../selftests/kvm/include/x86_64/sev.h        |  62 ++++
>   tools/testing/selftests/kvm/lib/x86_64/sev.c  | 303 ++++++++++++++++++
>   3 files changed, 366 insertions(+)
>   create mode 100644 tools/testing/selftests/kvm/include/x86_64/sev.h
>   create mode 100644 tools/testing/selftests/kvm/lib/x86_64/sev.c
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 5832f510a16c..c7a5e1c69e0c 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -35,6 +35,7 @@ endif
>   
>   LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/rbtree.c lib/sparsebit.c lib/test_util.c lib/guest_modes.c lib/perf_test_util.c
>   LIBKVM_x86_64 = lib/x86_64/apic.c lib/x86_64/processor.c lib/x86_64/vmx.c lib/x86_64/svm.c lib/x86_64/ucall.c lib/x86_64/handlers.S
> +LIBKVM_x86_64 += lib/x86_64/sev.c
>   LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c lib/aarch64/handlers.S
>   LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c lib/s390x/diag318_test_handler.c
>   
> diff --git a/tools/testing/selftests/kvm/include/x86_64/sev.h b/tools/testing/selftests/kvm/include/x86_64/sev.h
> new file mode 100644
> index 000000000000..d2f41b131ecc
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/include/x86_64/sev.h
> @@ -0,0 +1,62 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Helpers used for SEV guests
> + *
> + * Copyright (C) 2021 Advanced Micro Devices
> + */
> +#ifndef SELFTEST_KVM_SEV_H
> +#define SELFTEST_KVM_SEV_H
> +
> +#include <stdint.h>
> +#include <stdbool.h>
> +#include "kvm_util.h"
> +
> +#define SEV_DEV_PATH		"/dev/sev"
> +#define SEV_FW_REQ_VER_MAJOR	1
> +#define SEV_FW_REQ_VER_MINOR	30
> +
> +#define SEV_POLICY_NO_DBG	(1UL << 0)
> +#define SEV_POLICY_ES		(1UL << 2)
> +
> +#define SEV_GUEST_ASSERT(sync, token, _cond) do {	\
> +	if (!(_cond))					\
> +		sev_guest_abort(sync, token, 0);	\
> +} while (0)
> +
> +enum {
> +	SEV_GSTATE_UNINIT = 0,
> +	SEV_GSTATE_LUPDATE,
> +	SEV_GSTATE_LSECRET,
> +	SEV_GSTATE_RUNNING,
> +};
> +
> +struct sev_sync_data {
> +	uint32_t token;
> +	bool pending;
> +	bool done;
> +	bool aborted;
> +	uint64_t info;
> +};
> +
> +struct sev_vm;
> +
> +void sev_guest_sync(struct sev_sync_data *sync, uint32_t token, uint64_t info);
> +void sev_guest_done(struct sev_sync_data *sync, uint32_t token, uint64_t info);
> +void sev_guest_abort(struct sev_sync_data *sync, uint32_t token, uint64_t info);
> +
> +void sev_check_guest_sync(struct kvm_run *run, struct sev_sync_data *sync,
> +			  uint32_t token);
> +void sev_check_guest_done(struct kvm_run *run, struct sev_sync_data *sync,
> +			  uint32_t token);
> +
> +void kvm_sev_ioctl(struct sev_vm *sev, int cmd, void *data);
> +struct kvm_vm *sev_get_vm(struct sev_vm *sev);
> +uint8_t sev_get_enc_bit(struct sev_vm *sev);
> +
> +struct sev_vm *sev_vm_create(uint32_t policy, uint64_t npages);
> +void sev_vm_free(struct sev_vm *sev);
> +void sev_vm_launch(struct sev_vm *sev);
> +void sev_vm_measure(struct sev_vm *sev, uint8_t *measurement);
> +void sev_vm_launch_finish(struct sev_vm *sev);
> +
> +#endif /* SELFTEST_KVM_SEV_H */
> diff --git a/tools/testing/selftests/kvm/lib/x86_64/sev.c b/tools/testing/selftests/kvm/lib/x86_64/sev.c
> new file mode 100644
> index 000000000000..adda3b396566
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/lib/x86_64/sev.c
> @@ -0,0 +1,303 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Helpers used for SEV guests
> + *
> + * Copyright (C) 2021 Advanced Micro Devices
> + */
> +
> +#include <stdint.h>
> +#include <stdbool.h>
> +#include "kvm_util.h"
> +#include "linux/psp-sev.h"
> +#include "processor.h"
> +#include "sev.h"
> +
> +#define PAGE_SHIFT		12
> +#define PAGE_SIZE		(1UL << PAGE_SHIFT)
> +
> +struct sev_vm {
> +	struct kvm_vm *vm;
> +	int fd;
> +	int enc_bit;
> +	uint32_t sev_policy;
> +};
> +
> +/* Helpers for coordinating between guests and test harness. */
> +
> +void sev_guest_sync(struct sev_sync_data *sync, uint32_t token, uint64_t info)
> +{
> +	sync->token = token;
> +	sync->info = info;
> +	sync->pending = true;
> +
> +	asm volatile("hlt" : : : "memory");
> +}
> +
> +void sev_guest_done(struct sev_sync_data *sync, uint32_t token, uint64_t info)
> +{
> +	while (true) {
> +		sync->done = true;
> +		sev_guest_sync(sync, token, info);
> +	}
> +}
> +
> +void sev_guest_abort(struct sev_sync_data *sync, uint32_t token, uint64_t info)
> +{
> +	while (true) {
> +		sync->aborted = true;
> +		sev_guest_sync(sync, token, info);
> +	}
> +}
> +
> +void sev_check_guest_sync(struct kvm_run *run, struct sev_sync_data *sync,
> +			  uint32_t token)
> +{
> +	TEST_ASSERT(run->exit_reason == KVM_EXIT_HLT,
> +		    "unexpected exit reason: %u (%s)",
> +		    run->exit_reason, exit_reason_str(run->exit_reason));
> +	TEST_ASSERT(sync->token == token,
> +		    "unexpected guest token, expected %d, got: %d", token,
> +		    sync->token);
> +	TEST_ASSERT(!sync->done, "unexpected guest state");
> +	TEST_ASSERT(!sync->aborted, "unexpected guest state");
> +	sync->pending = false;
> +}
> +
> +void sev_check_guest_done(struct kvm_run *run, struct sev_sync_data *sync,
> +			  uint32_t token)
> +{
> +	TEST_ASSERT(run->exit_reason == KVM_EXIT_HLT,
> +		    "unexpected exit reason: %u (%s)",
> +		    run->exit_reason, exit_reason_str(run->exit_reason));
> +	TEST_ASSERT(sync->token == token,
> +		    "unexpected guest token, expected %d, got: %d", token,
> +		    sync->token);
> +	TEST_ASSERT(sync->done, "unexpected guest state");
> +	TEST_ASSERT(!sync->aborted, "unexpected guest state");
> +	sync->pending = false;
> +}
> +
> +/* Common SEV helpers/accessors. */
> +
> +struct kvm_vm *sev_get_vm(struct sev_vm *sev)
> +{
> +	return sev->vm;
> +}
> +
> +uint8_t sev_get_enc_bit(struct sev_vm *sev)
> +{
> +	return sev->enc_bit;
> +}
> +
> +void sev_ioctl(int sev_fd, int cmd, void *data)
> +{
> +	int ret;
> +	struct sev_issue_cmd arg;
> +
> +	arg.cmd = cmd;
> +	arg.data = (unsigned long)data;
> +	ret = ioctl(sev_fd, SEV_ISSUE_CMD, &arg);
> +	TEST_ASSERT(ret == 0,
> +		    "SEV ioctl %d failed, error: %d, fw_error: %d",
> +		    cmd, ret, arg.error);
> +}
> +
> +void kvm_sev_ioctl(struct sev_vm *sev, int cmd, void *data)
> +{
> +	struct kvm_sev_cmd arg = {0};
> +	int ret;
> +
> +	arg.id = cmd;
> +	arg.sev_fd = sev->fd;
> +	arg.data = (__u64)data;
> +
> +	ret = ioctl(vm_get_fd(sev->vm), KVM_MEMORY_ENCRYPT_OP, &arg);
> +	TEST_ASSERT(ret == 0,
> +		    "SEV KVM ioctl %d failed, rc: %i errno: %i (%s), fw_error: %d",
> +		    cmd, ret, errno, strerror(errno), arg.error);
> +}
> +
> +/* Local helpers. */
> +
> +static void
> +sev_register_user_range(struct sev_vm *sev, void *hva, uint64_t size)


Since 'region' is used in every naming, it's better to call it 
sev_register_user_region or sev_register_userspace_region for the sake 
of consistency.

> +{
> +	struct kvm_enc_region range = {0};
> +	int ret;
> +
> +	pr_debug("register_user_range: hva: %p, size: %lu\n", hva, size);
> +
> +	range.addr = (__u64)hva;
> +	range.size = size;
> +
> +	ret = ioctl(vm_get_fd(sev->vm), KVM_MEMORY_ENCRYPT_REG_REGION, &range);
> +	TEST_ASSERT(ret == 0, "failed to register user range, errno: %i\n", errno);
> +}
> +
> +static void
> +sev_encrypt_phy_range(struct sev_vm *sev, vm_paddr_t gpa, uint64_t size)
> +{
> +	struct kvm_sev_launch_update_data ksev_update_data = {0};
> +
> +	pr_debug("encrypt_phy_range: addr: 0x%lx, size: %lu\n", gpa, size);
> +
> +	ksev_update_data.uaddr = (__u64)addr_gpa2hva(sev->vm, gpa);
> +	ksev_update_data.len = size;
> +
> +	kvm_sev_ioctl(sev, KVM_SEV_LAUNCH_UPDATE_DATA, &ksev_update_data);
> +}
> +
> +static void sev_encrypt(struct sev_vm *sev)
> +{
> +	struct sparsebit *enc_phy_pages;
> +	struct kvm_vm *vm = sev->vm;
> +	sparsebit_idx_t pg = 0;
> +	vm_paddr_t gpa_start;
> +	uint64_t memory_size;
> +
> +	/* Only memslot 0 supported for now. */
> +	enc_phy_pages = vm_get_encrypted_phy_pages(sev->vm, 0, &gpa_start, &memory_size);


vm_get_encrypted_phy_pages() allocates a duplicate sparsebit. I am 
wondering if it is possible for the function to just give a pointer to 
'region->encrypted_phy_pages' so the allocation and freeing of memory 
can be avoided.

> +	TEST_ASSERT(enc_phy_pages, "Unable to retrieve encrypted pages bitmap");
> +	while (pg < (memory_size / vm_get_page_size(vm))) {
> +		sparsebit_idx_t pg_cnt;
> +
> +		if (sparsebit_is_clear(enc_phy_pages, pg)) {
> +			pg = sparsebit_next_set(enc_phy_pages, pg);
> +			if (!pg)
> +				break;
> +		}
> +
> +		pg_cnt = sparsebit_next_clear(enc_phy_pages, pg) - pg;
> +		if (pg_cnt <= 0)
> +			pg_cnt = 1;
> +
> +		sev_encrypt_phy_range(sev,
> +				      gpa_start + pg * vm_get_page_size(vm),
> +				      pg_cnt * vm_get_page_size(vm));
> +		pg += pg_cnt;
> +	}
> +
> +	sparsebit_free(&enc_phy_pages);
> +}
> +
> +/* SEV VM implementation. */
> +
> +static struct sev_vm *sev_common_create(struct kvm_vm *vm)


Can there be a better name like, sev_vm_alloc because it's essentially 
allocating and initializing a sev_vm data structure.

> +{
> +	struct sev_user_data_status sev_status = {0};
> +	uint32_t eax, ebx, ecx, edx;
> +	struct sev_vm *sev;
> +	int sev_fd;
> +
> +	sev_fd = open(SEV_DEV_PATH, O_RDWR);
> +	if (sev_fd < 0) {
> +		pr_info("Failed to open SEV device, path: %s, error: %d, skipping test.\n",
> +			SEV_DEV_PATH, sev_fd);
> +		return NULL;
> +	}
> +
> +	sev_ioctl(sev_fd, SEV_PLATFORM_STATUS, &sev_status);
> +
> +	if (!(sev_status.api_major > SEV_FW_REQ_VER_MAJOR ||
> +	      (sev_status.api_major == SEV_FW_REQ_VER_MAJOR &&
> +	       sev_status.api_minor >= SEV_FW_REQ_VER_MINOR))) {
> +		pr_info("SEV FW version too old. Have API %d.%d (build: %d), need %d.%d, skipping test.\n",
> +			sev_status.api_major, sev_status.api_minor, sev_status.build,
> +			SEV_FW_REQ_VER_MAJOR, SEV_FW_REQ_VER_MINOR);
> +		return NULL;
> +	}
> +
> +	sev = calloc(1, sizeof(*sev));
> +	sev->fd = sev_fd;
> +	sev->vm = vm;
> +
> +	/* Get encryption bit via CPUID. */
> +	eax = 0x8000001f;
> +	ecx = 0;
> +	cpuid(&eax, &ebx, &ecx, &edx);
> +	sev->enc_bit = ebx & 0x3F;
> +
> +	return sev;
> +}
> +
> +static void sev_common_free(struct sev_vm *sev)
> +{
> +	close(sev->fd);
> +	free(sev);
> +}
> +
> +struct sev_vm *sev_vm_create(uint32_t policy, uint64_t npages)
> +{
> +	struct sev_vm *sev;
> +	struct kvm_vm *vm;
> +
> +	/* Need to handle memslots after init, and after setting memcrypt. */
> +	vm = vm_create(VM_MODE_DEFAULT, 0, O_RDWR);
> +	sev = sev_common_create(vm);
> +	if (!sev)
> +		return NULL;
> +	sev->sev_policy = policy;
> +
> +	kvm_sev_ioctl(sev, KVM_SEV_INIT, NULL);
> +
> +	vm_set_memory_encryption(vm, true, true, sev->enc_bit);
> +	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, 0, 0, npages, 0);
> +	sev_register_user_range(sev, addr_gpa2hva(vm, 0), npages * vm_get_page_size(vm));
> +
> +	pr_info("SEV guest created, policy: 0x%x, size: %lu KB\n",
> +		sev->sev_policy, npages * vm_get_page_size(vm) / 1024);
> +
> +	return sev;
> +}
> +
> +void sev_vm_free(struct sev_vm *sev)
> +{
> +	kvm_vm_free(sev->vm);
> +	sev_common_free(sev);
> +}
> +
> +void sev_vm_launch(struct sev_vm *sev)
> +{
> +	struct kvm_sev_launch_start ksev_launch_start = {0};
> +	struct kvm_sev_guest_status ksev_status = {0};
> +
> +	ksev_launch_start.policy = sev->sev_policy;
> +	kvm_sev_ioctl(sev, KVM_SEV_LAUNCH_START, &ksev_launch_start);
> +	kvm_sev_ioctl(sev, KVM_SEV_GUEST_STATUS, &ksev_status);
> +	TEST_ASSERT(ksev_status.policy == sev->sev_policy, "Incorrect guest policy.");
> +	TEST_ASSERT(ksev_status.state == SEV_GSTATE_LUPDATE,
> +		    "Unexpected guest state: %d", ksev_status.state);
> +
> +	sev_encrypt(sev);
> +}
> +
> +void sev_vm_measure(struct sev_vm *sev, uint8_t *measurement)
> +{
> +	struct kvm_sev_launch_measure ksev_launch_measure = {0};
> +	struct kvm_sev_guest_status ksev_guest_status = {0};
> +
> +	ksev_launch_measure.len = 256;
> +	ksev_launch_measure.uaddr = (__u64)measurement;
> +	kvm_sev_ioctl(sev, KVM_SEV_LAUNCH_MEASURE, &ksev_launch_measure);
> +
> +	/* Measurement causes a state transition, check that. */
> +	kvm_sev_ioctl(sev, KVM_SEV_GUEST_STATUS, &ksev_guest_status);
> +	TEST_ASSERT(ksev_guest_status.state == SEV_GSTATE_LSECRET,
> +		    "Unexpected guest state: %d", ksev_guest_status.state);
> +}
> +
> +void sev_vm_launch_finish(struct sev_vm *sev)
> +{
> +	struct kvm_sev_guest_status ksev_status = {0};
> +
> +	kvm_sev_ioctl(sev, KVM_SEV_GUEST_STATUS, &ksev_status);
> +	TEST_ASSERT(ksev_status.state == SEV_GSTATE_LUPDATE ||
> +		    ksev_status.state == SEV_GSTATE_LSECRET,
> +		    "Unexpected guest state: %d", ksev_status.state);
> +
> +	kvm_sev_ioctl(sev, KVM_SEV_LAUNCH_FINISH, NULL);
> +
> +	kvm_sev_ioctl(sev, KVM_SEV_GUEST_STATUS, &ksev_status);
> +	TEST_ASSERT(ksev_status.state == SEV_GSTATE_RUNNING,
> +		    "Unexpected guest state: %d", ksev_status.state);
> +}