diff options
| author | Reinette Chatre <reinette.chatre@intel.com> | 2024-06-12 11:16:11 -0700 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2024-06-28 11:40:38 -0700 |
| commit | 6b878cbb87bf4fc4c07906ada431624911e3d85a (patch) | |
| tree | 140c95a5508b952994acd1a0992ab14536a518ee | |
| parent | dd103407ca315b467074d74b3580abe210c4c695 (diff) | |
KVM: selftests: Add guest udelay() utility for x86
Add udelay() for x86 tests to allow busy waiting in the guest for a
specific duration, and to match ARM and RISC-V's udelay() in the hopes
of eventually making udelay() available on all architectures.
Get the guest's TSC frequency using KVM_GET_TSC_KHZ and expose it to all
VMs via a new global, guest_tsc_khz. Assert that KVM_GET_TSC_KHZ returns
a valid frequency, instead of simply skipping tests, which would require
detecting which tests actually need/want udelay(). KVM hasn't returned an
error for KVM_GET_TSC_KHZ since commit cc578287e322 ("KVM: Infrastructure
for software and hardware based TSC rate scaling"), which predates KVM
selftests by 6+ years (KVM_GET_TSC_KHZ itself predates KVM selftest by 7+
years).
Note, if the GUEST_ASSERT() in udelay() somehow fires and the test doesn't
check for guest asserts, then the test will fail with a very cryptic
message. But fixing that, e.g. by automatically handling guest asserts,
is a much larger task, and practically speaking the odds of a test afoul
of this wart are infinitesimally small.
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Link: https://lore.kernel.org/r/5aa86285d1c1d7fe1960e3fe490f4b22273977e6.1718214999.git.reinette.chatre@intel.com
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
| -rw-r--r-- | tools/testing/selftests/kvm/include/x86_64/processor.h | 18 | ||||
| -rw-r--r-- | tools/testing/selftests/kvm/lib/x86_64/processor.c | 11 |
2 files changed, 29 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h index 8eb57de0b587..8501735c6f41 100644 --- a/tools/testing/selftests/kvm/include/x86_64/processor.h +++ b/tools/testing/selftests/kvm/include/x86_64/processor.h @@ -23,6 +23,7 @@ extern bool host_cpu_is_intel; extern bool host_cpu_is_amd; +extern uint64_t guest_tsc_khz; /* Forced emulation prefix, used to invoke the emulator unconditionally. */ #define KVM_FEP "ud2; .byte 'k', 'v', 'm';" @@ -815,6 +816,23 @@ static inline void cpu_relax(void) asm volatile("rep; nop" ::: "memory"); } +static inline void udelay(unsigned long usec) +{ + uint64_t start, now, cycles; + + GUEST_ASSERT(guest_tsc_khz); + cycles = guest_tsc_khz / 1000 * usec; + + /* + * Deliberately don't PAUSE, a.k.a. cpu_relax(), so that the delay is + * as accurate as possible, e.g. doesn't trigger PAUSE-Loop VM-Exits. + */ + start = rdtsc(); + do { + now = rdtsc(); + } while (now - start < cycles); +} + #define ud2() \ __asm__ __volatile__( \ "ud2\n" \ diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c index c664e446136b..d547f121813d 100644 --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c @@ -25,6 +25,7 @@ vm_vaddr_t exception_handlers; bool host_cpu_is_amd; bool host_cpu_is_intel; bool is_forced_emulation_enabled; +uint64_t guest_tsc_khz; static void regs_dump(FILE *stream, struct kvm_regs *regs, uint8_t indent) { @@ -616,6 +617,11 @@ void assert_on_unhandled_exception(struct kvm_vcpu *vcpu) void kvm_arch_vm_post_create(struct kvm_vm *vm) { + int r; + + TEST_ASSERT(kvm_has_cap(KVM_CAP_GET_TSC_KHZ), + "Require KVM_GET_TSC_KHZ to provide udelay() to guest."); + vm_create_irqchip(vm); vm_init_descriptor_tables(vm); @@ -628,6 +634,11 @@ void kvm_arch_vm_post_create(struct kvm_vm *vm) vm_sev_ioctl(vm, KVM_SEV_INIT2, &init); } + + r = __vm_ioctl(vm, KVM_GET_TSC_KHZ, NULL); + TEST_ASSERT(r > 0, "KVM_GET_TSC_KHZ did not provide a valid TSC frequency."); + guest_tsc_khz = r; + sync_global_to_guest(vm, guest_tsc_khz); } void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code) |