Re: [RFC PATCH 1/2] KVM: arm64: nv: selftests: Add guest hypervisor test

Hi Marc,

On 07-02-2025 02:44 am, Marc Zyngier wrote:

On Thu, 06 Feb 2025 16:41:19 +0000, Ganapatrao Kulkarni gankulkarni@os.amperecomputing.com wrote:

...

This patch adds the required changes to init vcpu in vEL2 context. Also adds a KVM selftest to execute guest code as a guest hypervisor(L1).

Signed-off-by: Ganapatrao Kulkarni gankulkarni@os.amperecomputing.com

tools/testing/selftests/kvm/Makefile.kvm | 1 + .../selftests/kvm/arm64/nv_guest_hypervisor.c | 83 +++++++++++++++++++ .../kvm/include/arm64/kvm_util_arch.h | 3 + .../selftests/kvm/include/arm64/nv_util.h | 28 +++++++ .../testing/selftests/kvm/include/kvm_util.h | 1 + .../selftests/kvm/lib/arm64/processor.c | 59 +++++++++---- 6 files changed, 161 insertions(+), 14 deletions(-) create mode 100644 tools/testing/selftests/kvm/arm64/nv_guest_hypervisor.c create mode 100644 tools/testing/selftests/kvm/include/arm64/nv_util.h

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm index 4277b983cace..a85d3bec9fb1 100644 --- a/tools/testing/selftests/kvm/Makefile.kvm +++ b/tools/testing/selftests/kvm/Makefile.kvm @@ -154,6 +154,7 @@ TEST_GEN_PROGS_arm64 += arm64/vgic_irq TEST_GEN_PROGS_arm64 += arm64/vgic_lpi_stress TEST_GEN_PROGS_arm64 += arm64/vpmu_counter_access TEST_GEN_PROGS_arm64 += arm64/no-vgic-v3 +TEST_GEN_PROGS_arm64 += arm64/nv_guest_hypervisor TEST_GEN_PROGS_arm64 += access_tracking_perf_test TEST_GEN_PROGS_arm64 += arch_timer TEST_GEN_PROGS_arm64 += coalesced_io_test diff --git a/tools/testing/selftests/kvm/arm64/nv_guest_hypervisor.c b/tools/testing/selftests/kvm/arm64/nv_guest_hypervisor.c new file mode 100644 index 000000000000..5aeefe43aff7 --- /dev/null +++ b/tools/testing/selftests/kvm/arm64/nv_guest_hypervisor.c @@ -0,0 +1,83 @@ +// SPDX-License-Identifier: GPL-2.0-only +/*

• • Copyright (c) 2025 Ampere Computing LLC
• */

+#include <kvm_util.h> +#include <nv_util.h> +#include <processor.h> +#include <vgic.h>

+static void guest_code(void) +{

• if (read_sysreg(CurrentEL) == CurrentEL_EL2)

• GUEST_PRINTF("Executing guest code in vEL2\n");
  

• else

• GUEST_FAIL("Fail to run in vEL2\n");
  

• GUEST_DONE();

+}

+static void guest_undef_handler(struct ex_regs *regs) +{

• GUEST_FAIL("Unexpected exception far_el1 = 0x%lx", read_sysreg(far_el1));

+}

+static void test_run_vcpu(struct kvm_vcpu *vcpu) +{

• struct ucall uc;
• do {

• vcpu_run(vcpu);
  

• switch (get_ucall(vcpu, &uc)) {
  

• case UCALL_ABORT:
  

• 	REPORT_GUEST_ASSERT(uc);
  

• 	break;
  

• case UCALL_PRINTF:
  

• 	printf("%s", uc.buffer);
  

• 	break;
  

• case UCALL_DONE:
  

• 	printf("Test PASS\n");
  

• 	break;
  

• default:
  

• 	TEST_FAIL("Unknown ucall %lu", uc.cmd);
  

• }
  

• } while (uc.cmd != UCALL_DONE);

+}

+static void test_nv_guest_hypervisor(void) +{

• struct kvm_vcpu *vcpu;
• struct kvm_vm *vm;
• struct kvm_vcpu_init init;
• int gic_fd;
• vm = vm_create(1);
• vm_ioctl(vm, KVM_ARM_PREFERRED_TARGET, &init);
• init.features[0] = 0;
• init_vcpu_nested(&init);
• vcpu = aarch64_vcpu_add(vm, 0, &init, guest_code);
• __TEST_REQUIRE(is_vcpu_nested(vcpu), "Failed to Enable NV");
• vm_init_descriptor_tables(vm);
• vcpu_init_descriptor_tables(vcpu);
• gic_fd = vgic_v3_setup(vm, 1, 64);
• __TEST_REQUIRE(gic_fd >= 0, "Failed to create vgic-v3");
• vm_install_sync_handler(vm, VECTOR_SYNC_CURRENT,

• 		ESR_ELx_EC_UNKNOWN, guest_undef_handler);
  

• test_run_vcpu(vcpu);
• kvm_vm_free(vm);

+}

+int main(int argc, char *argv[]) +{

• TEST_REQUIRE(kvm_has_cap(KVM_CAP_ARM_EL2));
• test_nv_guest_hypervisor();
• return 0;

+} diff --git a/tools/testing/selftests/kvm/include/arm64/kvm_util_arch.h b/tools/testing/selftests/kvm/include/arm64/kvm_util_arch.h index e43a57d99b56..ab5279c24413 100644 --- a/tools/testing/selftests/kvm/include/arm64/kvm_util_arch.h +++ b/tools/testing/selftests/kvm/include/arm64/kvm_util_arch.h @@ -2,6 +2,9 @@ #ifndef SELFTEST_KVM_UTIL_ARCH_H #define SELFTEST_KVM_UTIL_ARCH_H +#define CurrentEL_EL1 (1 << 2) +#define CurrentEL_EL2 (2 << 2)

• struct kvm_vm_arch {};

#endif // SELFTEST_KVM_UTIL_ARCH_H diff --git a/tools/testing/selftests/kvm/include/arm64/nv_util.h b/tools/testing/selftests/kvm/include/arm64/nv_util.h new file mode 100644 index 000000000000..4fecf1f18554 --- /dev/null +++ b/tools/testing/selftests/kvm/include/arm64/nv_util.h @@ -0,0 +1,28 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/*

• • Copyright (c) 2025 Ampere Computing
• */

+#ifndef SELFTEST_NV_UTIL_H +#define SELFTEST_NV_UTIL_H

+#include <linux/bitmap.h>

+/* NV helpers */ +static inline void init_vcpu_nested(struct kvm_vcpu_init *init) +{

• init->features[0] |= (1 << KVM_ARM_VCPU_HAS_EL2);

+}

+static inline bool kvm_arm_vcpu_has_el2(struct kvm_vcpu_init *init) +{

• unsigned long features = init->features[0];
• return test_bit(KVM_ARM_VCPU_HAS_EL2, &features);

+}

+static inline bool is_vcpu_nested(struct kvm_vcpu *vcpu) +{

• return vcpu->nested;

+}

+#endif /* SELFTEST_NV_UTIL_H */ diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h index 4c4e5a847f67..8c53dbc17f8f 100644 --- a/tools/testing/selftests/kvm/include/kvm_util.h +++ b/tools/testing/selftests/kvm/include/kvm_util.h @@ -58,6 +58,7 @@ struct kvm_vcpu { struct kvm_dirty_gfn *dirty_gfns; uint32_t fetch_index; uint32_t dirty_gfns_count;

• bool nested; };

struct userspace_mem_regions { diff --git a/tools/testing/selftests/kvm/lib/arm64/processor.c b/tools/testing/selftests/kvm/lib/arm64/processor.c index 7ba3aa3755f3..35ba2ace61a2 100644 --- a/tools/testing/selftests/kvm/lib/arm64/processor.c +++ b/tools/testing/selftests/kvm/lib/arm64/processor.c @@ -10,6 +10,7 @@ #include "guest_modes.h" #include "kvm_util.h" +#include "nv_util.h" #include "processor.h" #include "ucall_common.h" @@ -258,14 +259,47 @@ void virt_arch_dump(FILE *stream, struct kvm_vm *vm, uint8_t indent) } } +static void aarch64_vcpu_set_reg(struct kvm_vcpu *vcpu, uint64_t sctlr_el1,

• 	uint64_t tcr_el1, uint64_t ttbr0_el1)
  

+{

• uint64_t fpen;
• /*

• * Enable FP/ASIMD to avoid trapping when accessing Q0-Q15
  

• * registers, which the variable argument list macros do.
  

• */
  

• fpen = 3 << 20;
• if (is_vcpu_nested(vcpu)) {

• vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_CPTR_EL2), fpen);
  

• vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_SCTLR_EL2), sctlr_el1);
  

• vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TCR_EL2), tcr_el1);
  

• vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_MAIR_EL2), DEFAULT_MAIR_EL1);
  

• vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TTBR0_EL2), ttbr0_el1);
  

• vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_TPIDR_EL2), vcpu->id);
  

How about some of the basics such as HCR_EL2, MDCR_EL2? A bunch of things there do have an impact on how the guest behaves, and relying on defaults feels like a bad idea.

Sure, I will try to have these registers also set to required value explicitly.

This also assumes VHE, without trying to enforce it.

Ok, I will try to set specific bits of HCR_EL2 to force it run in VHE.

Finally, how to you plan to make all the existing tests run as EL2 guests if TPIDR_EL1 isn't populated with the expected value? Surely you need to change the read side...

OK, I have not yet tried running existing tests modifying to run as EL2 guests. I will try to run them modifying to run in vEL2.

Should we modify them to run as EL2 guests by default, if the host supports/detected NV? or command line argument based run? either in El1(default) or in EL2?

BTW, I have also ran all existing tests on L1, most of the tests are passing(atleast I did not see any failure prints).

arm64/debug-exceptions is failing on L1 and needs to be debugged/fixed/skipped. arm64/arch_timer_edge_cases fails on both L0 and L1.