On Mon, Jun 10, 2024, Reinette Chatre wrote:
> diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
> index 8eb57de0b587..b473f210ba6c 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 unsigned int tsc_khz;
>
> /* Forced emulation prefix, used to invoke the emulator unconditionally. */
> #define KVM_FEP "ud2; .byte 'k', 'v', 'm';"
> @@ -815,6 +816,20 @@ static inline void cpu_relax(void)
> asm volatile("rep; nop" ::: "memory");
> }
>
> +static inline void udelay(unsigned long usec)
uint64_t instead of unsigned long? Practically speaking it doesn't change anything,
but I don't see any reason to mix "unsigned long" and "uint64_t", e.g. the max
delay isn't a property of the address space.
> +{
> + unsigned long cycles = tsc_khz / 1000 * usec;
> + uint64_t start, now;
> +
> + start = rdtsc();
> + for (;;) {
> + now = rdtsc();
> + if (now - start >= cycles)
> + break;
> + cpu_relax();
> + }
> +}
> +
> #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..ff579674032f 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;
> +unsigned int tsc_khz;
Slight preference for uint32_t, mostly because KVM stores its version as a u32.
> static void regs_dump(FILE *stream, struct kvm_regs *regs, uint8_t indent)
> {
> @@ -616,6 +617,8 @@ void assert_on_unhandled_exception(struct kvm_vcpu *vcpu)
>
> void kvm_arch_vm_post_create(struct kvm_vm *vm)
> {
> + int r;
> +
> vm_create_irqchip(vm);
> vm_init_descriptor_tables(vm);
>
> @@ -628,6 +631,15 @@ void kvm_arch_vm_post_create(struct kvm_vm *vm)
>
> vm_sev_ioctl(vm, KVM_SEV_INIT2, &init);
> }
> +
> + if (kvm_has_cap(KVM_CAP_GET_TSC_KHZ)) {
I think we should make this a TEST_REQUIRE(), or maybe even a TEST_ASSERT().
Support for KVM_GET_TSC_KHZ predates KVM selftests by 7+ years.
> + r = __vm_ioctl(vm, KVM_GET_TSC_KHZ, NULL);
> + if (r < 0)
Heh, the docs are stale. KVM hasn't returned an error since commit cc578287e322
("KVM: Infrastructure for software and hardware based TSC rate scaling"), which
again predates selftests by many years (6+ in this case). To make our lives
much simpler, I think we should assert that KVM_GET_TSC_KHZ succeeds, and maybe
throw in a GUEST_ASSERT(thz_khz) in udelay()?
E.g. as is, if KVM_GET_TSC_KHZ is allowed to fail, then we risk having to deal
with weird failures due to udelay() unexpectedly doing nothing.
> + tsc_khz = 0;
> + else
> + tsc_khz = r;
> + sync_global_to_guest(vm, tsc_khz);
> + }
> }
>
> void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code)
> --
> 2.34.1
>
