Re: [PATCH v5 08/10] selftests: KVM: aarch64: Introduce hypercall ABI test

From: Raghavendra Rao Ananta
Date: Wed Apr 13 2022 - 13:32:44 EST

On Wed, Apr 13, 2022 at 2:07 AM Gavin Shan <gshan@xxxxxxxxxx> wrote:
>
> Hi Raghavendra,
>
> On 4/7/22 9:16 AM, Raghavendra Rao Ananta wrote:
> > Introduce a KVM selftest to check the hypercall interface
> > for arm64 platforms. The test validates the user-space's
> > IOCTL interface to read/write the psuedo-firmware registers
> > as well as its effects on the guest upon certain configurations.
> >
> > Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> > ---
> > tools/testing/selftests/kvm/.gitignore | 1 +
> > tools/testing/selftests/kvm/Makefile | 1 +
> > .../selftests/kvm/aarch64/hypercalls.c | 344 ++++++++++++++++++
> > 3 files changed, 346 insertions(+)
> > create mode 100644 tools/testing/selftests/kvm/aarch64/hypercalls.c
> >
>
> To be more precise, s/IOCTL/{GET,SET}_ONE_REG ?
>
Sure, I think that'll be better.

> > diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
> > index e82b816a6608..7ef52b3b1560 100644
> > --- a/tools/testing/selftests/kvm/.gitignore
> > +++ b/tools/testing/selftests/kvm/.gitignore
> > @@ -2,6 +2,7 @@
> > /aarch64/arch_timer
> > /aarch64/debug-exceptions
> > /aarch64/get-reg-list
> > +/aarch64/hypercalls
> > /aarch64/psci_test
> > /aarch64/vgic_init
> > /aarch64/vgic_irq
> > diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> > index 2f74f502de65..af4cb88bcf83 100644
> > --- a/tools/testing/selftests/kvm/Makefile
> > +++ b/tools/testing/selftests/kvm/Makefile
> > @@ -105,6 +105,7 @@ TEST_GEN_PROGS_x86_64 += system_counter_offset_test
> > TEST_GEN_PROGS_aarch64 += aarch64/arch_timer
> > TEST_GEN_PROGS_aarch64 += aarch64/debug-exceptions
> > TEST_GEN_PROGS_aarch64 += aarch64/get-reg-list
> > +TEST_GEN_PROGS_aarch64 += aarch64/hypercalls
> > TEST_GEN_PROGS_aarch64 += aarch64/psci_test
> > TEST_GEN_PROGS_aarch64 += aarch64/vgic_init
> > TEST_GEN_PROGS_aarch64 += aarch64/vgic_irq
> > diff --git a/tools/testing/selftests/kvm/aarch64/hypercalls.c b/tools/testing/selftests/kvm/aarch64/hypercalls.c
> > new file mode 100644
> > index 000000000000..9941fb75772a
> > --- /dev/null
> > +++ b/tools/testing/selftests/kvm/aarch64/hypercalls.c
> > @@ -0,0 +1,344 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +
> > +/* hypercalls: Check the ARM64's psuedo-firmware bitmap register interface.
> > + *
> > + * The test validates the basic hypercall functionalities that are exposed
> > + * via the psuedo-firmware bitmap register. This includes the registers'
> > + * read/write behavior before and after the VM has started, and if the
> > + * hypercalls are properly masked or unmasked to the guest when disabled or
> > + * enabled from the KVM userspace, respectively.
> > + */
> > +
> > +#include <errno.h>
> > +#include <linux/arm-smccc.h>
> > +#include <asm/kvm.h>
> > +#include <kvm_util.h>
> > +
> > +#include "processor.h"
> > +
> > +#define FW_REG_ULIMIT_VAL(max_feat_bit) (GENMASK_ULL(max_feat_bit, 0))
> > +
> > +/* Last valid bits of the bitmapped firmware registers */
> > +#define KVM_REG_ARM_STD_BMAP_BIT_MAX 0
> > +#define KVM_REG_ARM_STD_HYP_BMAP_BIT_MAX 0
> > +#define KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_MAX 1
> > +
> > +struct kvm_fw_reg_info {
> > + uint64_t reg; /* Register definition */
> > + uint64_t max_feat_bit; /* Bit that represents the upper limit of the feature-map */
> > +};
> > +
> > +#define FW_REG_INFO(r, bit_max) \
> > + { \
> > + .reg = r, \
> > + .max_feat_bit = bit_max, \
> > + }
> > +
> > +static const struct kvm_fw_reg_info fw_reg_info[] = {
> > + FW_REG_INFO(KVM_REG_ARM_STD_BMAP, KVM_REG_ARM_STD_BMAP_BIT_MAX),
> > + FW_REG_INFO(KVM_REG_ARM_STD_HYP_BMAP, KVM_REG_ARM_STD_HYP_BMAP_BIT_MAX),
> > + FW_REG_INFO(KVM_REG_ARM_VENDOR_HYP_BMAP, KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_MAX),
> > +};
> > +
>
> This can be simplifed by:
>
> #define FW_REG_INFO(r) \
> { .reg = r, \
> .max_feat_bit = r_##BIT_MAX, \
> }
>
> static const struct kvm_fw_reg_info fw_reg_info[] = {
> FW_REG_INFO(KVM_REG_ARM_STD_BMAP),
> FW_REG_INFO(KVM_REG_ARM_STD_HYP_BMAP),
> FW_REG_INFO(KVM_REG_ARM_VENDOR_HYP_BMAP),
> };
>
Yes, probably that looks better. Thanks for the suggestion.

> > +enum test_stage {
> > + TEST_STAGE_REG_IFACE,
> > + TEST_STAGE_HVC_IFACE_FEAT_DISABLED,
> > + TEST_STAGE_HVC_IFACE_FEAT_ENABLED,
> > + TEST_STAGE_HVC_IFACE_FALSE_INFO,
> > + TEST_STAGE_END,
> > +};
> > +
> > +static int stage;
> > +
>
> I think it'd better to initialize @stage to TEST_STAGE_REG_IFACE.
>
Will do.
> > +struct test_hvc_info {
> > + uint32_t func_id;
> > + int64_t arg0;
> > +};
> > +
> > +#define TEST_HVC_INFO(f, a0) \
> > + { \
> > + .func_id = f, \
> > + .arg0 = a0, \
> > + }
> > +
>
> According to those functions (smccc_get_{function, argx}()) defined
> in include/kvm/arm_hypercalls.h, @arg0 would have type of "uint64_t"
> if I'm correct. Besides, @func_id is arg0 and arg0 should be arg1?
> So if I'm correct, this would be:
>
> struct test_hvc_info {
> uint32_t func_id;
> uint64_t arg1
> };
>
Thanks for noticing this! I'll change it to 'unit64'. Regarding the
argument naming, I understand that it's a little confusing. I went
with 'arg0' to align with the selftest library's convention. But, I
agree that it's not aligned with what the kernel is used to.

Oliver, do you think we can start the argument naming from a1/arg1 in [1]?

> > +static const struct test_hvc_info hvc_info[] = {
> > + /* KVM_REG_ARM_STD_BMAP */
> > + TEST_HVC_INFO(ARM_SMCCC_TRNG_VERSION, 0),
> > + TEST_HVC_INFO(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND64),
> > + TEST_HVC_INFO(ARM_SMCCC_TRNG_GET_UUID, 0),
> > + TEST_HVC_INFO(ARM_SMCCC_TRNG_RND32, 0),
> > + TEST_HVC_INFO(ARM_SMCCC_TRNG_RND64, 0),
> > +
> > + /* KVM_REG_ARM_STD_HYP_BMAP */
> > + TEST_HVC_INFO(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, ARM_SMCCC_HV_PV_TIME_FEATURES),
> > + TEST_HVC_INFO(ARM_SMCCC_HV_PV_TIME_FEATURES, ARM_SMCCC_HV_PV_TIME_ST),
> > + TEST_HVC_INFO(ARM_SMCCC_HV_PV_TIME_ST, 0),
> > +
> > + /* KVM_REG_ARM_VENDOR_HYP_BMAP */
> > + TEST_HVC_INFO(ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID,
> > + ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID),
> > + TEST_HVC_INFO(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID, KVM_PTP_VIRT_COUNTER),
> > +};
> > +
> > +/* Feed false hypercall info to test the KVM behavior */
> > +static const struct test_hvc_info false_hvc_info[] = {
> > + /* Feature support check against a different family of hypercalls */
> > + TEST_HVC_INFO(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID),
> > + TEST_HVC_INFO(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, ARM_SMCCC_TRNG_RND64),
> > + TEST_HVC_INFO(ARM_SMCCC_HV_PV_TIME_FEATURES, ARM_SMCCC_TRNG_RND64),
> > +};
> > +
> > +static void guest_test_hvc(const struct test_hvc_info *hc_info)
> > +{
> > + unsigned int i;
> > + struct arm_smccc_res res;
> > + unsigned int hvc_info_arr_sz;
> > +
> > + hvc_info_arr_sz =
> > + hc_info == hvc_info ? ARRAY_SIZE(hvc_info) : ARRAY_SIZE(false_hvc_info);
> > +
> > + for (i = 0; i < hvc_info_arr_sz; i++, hc_info++) {
> > +
> > + memset(&res, 0, sizeof(res));
> > + smccc_hvc(hc_info->func_id, hc_info->arg0, 0, 0, 0, 0, 0, 0, &res);
> > +
>
> Unnecessary empty line before memset(). I don't find where smccc_hvc()
> is defined.
>
I can clear the line and for the definition of smccc_hvc(), I applied
Oliver's patch [1].

> > + switch (stage) {
> > + case TEST_STAGE_HVC_IFACE_FEAT_DISABLED:
> > + case TEST_STAGE_HVC_IFACE_FALSE_INFO:
> > + GUEST_ASSERT_3(res.a0 == SMCCC_RET_NOT_SUPPORTED,
> > + res.a0, hc_info->func_id, hc_info->arg0);
> ^^
>
> It seems the code here isn't properly aligned. Maybe it's your
> preference :)
>
I think my editor is acting weird. I'll check again. Thanks for catching this!

> > + break;
> > + case TEST_STAGE_HVC_IFACE_FEAT_ENABLED:
> > + GUEST_ASSERT_3(res.a0 != SMCCC_RET_NOT_SUPPORTED,
> > + res.a0, hc_info->func_id, hc_info->arg0);
> > + break;
> > + default:
> > + GUEST_ASSERT_1(0, stage);
> > + }
> > + }
> > +}
> > +
> > +static void guest_code(void)
> > +{
> > + while (stage != TEST_STAGE_END) {
> > + switch (stage) {
> > + case TEST_STAGE_REG_IFACE:
> > + break;
> > + case TEST_STAGE_HVC_IFACE_FEAT_DISABLED:
> > + case TEST_STAGE_HVC_IFACE_FEAT_ENABLED:
> > + guest_test_hvc(hvc_info);
> > + break;
> > + case TEST_STAGE_HVC_IFACE_FALSE_INFO:
> > + guest_test_hvc(false_hvc_info);
> > + break;
> > + default:
> > + GUEST_ASSERT_1(0, stage);
> > + }
> > +
> > + GUEST_SYNC(stage);
> > + }
> > +
> > + GUEST_DONE();
> > +}
> > +
> > +static int set_fw_reg(struct kvm_vm *vm, uint64_t id, uint64_t val)
> > +{
> > + struct kvm_one_reg reg = {
> > + .id = id,
> > + .addr = (uint64_t)&val,
> > + };
> > +
> > + return _vcpu_ioctl(vm, 0, KVM_SET_ONE_REG, &reg);
> > +}
> > +
> > +static void get_fw_reg(struct kvm_vm *vm, uint64_t id, uint64_t *addr)
> > +{
> > + struct kvm_one_reg reg = {
> > + .id = id,
> > + .addr = (uint64_t)addr,
> > + };
> > +
> > + vcpu_ioctl(vm, 0, KVM_GET_ONE_REG, &reg);
> > +}
> > +
> > +struct st_time {
> > + uint32_t rev;
> > + uint32_t attr;
> > + uint64_t st_time;
> > +};
> > +
> > +#define STEAL_TIME_SIZE ((sizeof(struct st_time) + 63) & ~63)
> > +#define ST_GPA_BASE (1 << 30)
> > +
> > +static void steal_time_init(struct kvm_vm *vm)
> > +{
> > + uint64_t st_ipa = (ulong)ST_GPA_BASE;
> > + unsigned int gpages;
> > + struct kvm_device_attr dev = {
> > + .group = KVM_ARM_VCPU_PVTIME_CTRL,
> > + .attr = KVM_ARM_VCPU_PVTIME_IPA,
> > + .addr = (uint64_t)&st_ipa,
> > + };
> > +
> > + gpages = vm_calc_num_guest_pages(VM_MODE_DEFAULT, STEAL_TIME_SIZE);
> > + vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, ST_GPA_BASE, 1, gpages, 0);
> > +
> > + vcpu_ioctl(vm, 0, KVM_SET_DEVICE_ATTR, &dev);
> > +}
> > +
>
> It might be helpful to do TEST_FAIL() on error returned from
> this vcpu_ioctl(), or skip those PVTIME SMCCC calls accordingly
> if the attribute isn't set successfully.
>
vcpu_ioctl() does a TEST_ASSERT() for us. Of course we can check it
ourselves and skip if needed, but don't you think that may go
unnoticed should any future changes tries to mess with
steal_time_init() incorrectly and we'd end up skipping the test
forever until we really notice skipped test?

> > +static void test_fw_regs_before_vm_start(struct kvm_vm *vm)
> > +{
> > + uint64_t val;
> > + unsigned int i;
> > + int ret;
> > +
> > + for (i = 0; i < ARRAY_SIZE(fw_reg_info); i++) {
> > + const struct kvm_fw_reg_info *reg_info = &fw_reg_info[i];
> > +
> > + /* First 'read' should be an upper limit of the features supported */
> > + get_fw_reg(vm, reg_info->reg, &val);
> > + TEST_ASSERT(val == FW_REG_ULIMIT_VAL(reg_info->max_feat_bit),
> > + "Expected all the features to be set for reg: 0x%lx; expected: 0x%llx; read: 0x%lx\n",
> > + reg_info->reg, GENMASK_ULL(reg_info->max_feat_bit, 0), val);
> > +
>
> s/GENMASK_ULL(...)/FW_REG_ULIMIT_VAL(...)
>
Right, that's better.

> > + /* Test a 'write' by disabling all the features of the register map */
> > + ret = set_fw_reg(vm, reg_info->reg, 0);
> > + TEST_ASSERT(ret == 0,
> > + "Failed to clear all the features of reg: 0x%lx; ret: %d\n",
> > + reg_info->reg, errno);
> > +
> > + get_fw_reg(vm, reg_info->reg, &val);
> > + TEST_ASSERT(val == 0,
> > + "Expected all the features to be cleared for reg: 0x%lx\n", reg_info->reg);
> > +
> > + /*
> > + * Test enabling a feature that's not supported.
> > + * Avoid this check if all the bits are occupied.
> > + */
> > + if (reg_info->max_feat_bit < 63) {
> > + ret = set_fw_reg(vm, reg_info->reg, BIT(reg_info->max_feat_bit + 1));
> > + TEST_ASSERT(ret != 0 && errno == EINVAL,
> > + "Unexpected behavior or return value (%d) while setting an unsupported feature for reg: 0x%lx\n",
> > + errno, reg_info->reg);
> > + }
> > + }
> > +}
> > +
> > +static void test_fw_regs_after_vm_start(struct kvm_vm *vm)
> > +{
> > + uint64_t val;
> > + unsigned int i;
> > + int ret;
> > +
> > + for (i = 0; i < ARRAY_SIZE(fw_reg_info); i++) {
> > + const struct kvm_fw_reg_info *reg_info = &fw_reg_info[i];
> > +
> > + /*
> > + * Before starting the VM, the test clears all the bits.
> > + * Check if that's still the case.
> > + */
> > + get_fw_reg(vm, reg_info->reg, &val);
> > + TEST_ASSERT(val == 0,
> > + "Expected all the features to be cleared for reg: 0x%lx\n",
> > + reg_info->reg);
> > +
> > + /*
> > + * Test setting the last read value. KVM should allow this
> > + * even if VM has started running.
> > + */
> > + ret = set_fw_reg(vm, reg_info->reg, val);
> > + TEST_ASSERT(ret == 0,
> > + "Failed to set the register with previously read value after Vm start for reg: 0x%lx; ret: %d\n",
> > + reg_info->reg, errno);
> > +
> > + /*
> > + * Set all the features for this register again. KVM shouldn't
> > + * allow this as the VM is running.
> > + */
> > + ret = set_fw_reg(vm, reg_info->reg, FW_REG_ULIMIT_VAL(reg_info->max_feat_bit));
> > + TEST_ASSERT(ret != 0 && errno == EBUSY,
> > + "Unexpected behavior or return value (%d) while setting a feature while VM is running for reg: 0x%lx\n",
> > + errno, reg_info->reg);
> > + }
> > +}
> > +
> > +static struct kvm_vm *test_vm_create(void)
> > +{
> > + struct kvm_vm *vm;
> > +
> > + vm = vm_create_default(0, 0, guest_code);
> > +
> > + ucall_init(vm, NULL);
> > + steal_time_init(vm);
> > +
> > + return vm;
> > +}
> > +
> > +static struct kvm_vm *test_guest_stage(struct kvm_vm *vm)
> > +{
> > + struct kvm_vm *ret_vm = vm;
> > +
> > + pr_debug("Stage: %d\n", stage);
> > +
> > + switch (stage) {
> > + case TEST_STAGE_REG_IFACE:
> > + test_fw_regs_after_vm_start(vm);
> > + break;
> > + case TEST_STAGE_HVC_IFACE_FEAT_DISABLED:
> > + /* Start a new VM so that all the features are now enabled by default */
> > + kvm_vm_free(vm);
> > + ret_vm = test_vm_create();
> > + break;
> > + case TEST_STAGE_HVC_IFACE_FEAT_ENABLED:
> > + case TEST_STAGE_HVC_IFACE_FALSE_INFO:
> > + break;
> > + default:
> > + TEST_FAIL("Unknown test stage: %d\n", stage);
> > + }
> > +
> > + stage++;
> > + sync_global_to_guest(vm, stage);
> > +
> > + return ret_vm;
> > +}
> > +
> > +static void test_run(void)
> > +{
> > + struct kvm_vm *vm;
> > + struct ucall uc;
> > + bool guest_done = false;
> > +
> > + vm = test_vm_create();
> > +
> > + test_fw_regs_before_vm_start(vm);
> > +
> > + while (!guest_done) {
> > + vcpu_run(vm, 0);
> > +
> > + switch (get_ucall(vm, 0, &uc)) {
> > + case UCALL_SYNC:
> > + vm = test_guest_stage(vm);
> > + break;
> > + case UCALL_DONE:
> > + guest_done = true;
> > + break;
> > + case UCALL_ABORT:
> > + TEST_FAIL("%s at %s:%ld\n\tvalues: 0x%lx, 0x%lx; 0x%lx, stage: %u",
> > + (const char *)uc.args[0], __FILE__, uc.args[1],
> > + uc.args[2], uc.args[3], uc.args[4], stage);
> > + break;
> > + default:
> > + TEST_FAIL("Unexpected guest exit\n");
> > + }
> > + }
> > +
> > + kvm_vm_free(vm);
> > +}
> > +
> > +int main(void)
> > +{
> > + setbuf(stdout, NULL);
> > +
> > + test_run();
> > + return 0;
> > +}
> >
>
> Thanks,
> Gavin
>

Thanks for taking the time to review.

Regards,
Raghavendra

[1]: https://lore.kernel.org/kvmarm/20220409184549.1681189-11-oupton@xxxxxxxxxx/T/#u