| Message ID | 5aa86285d1c1d7fe1960e3fe490f4b22273977e6.1718214999.git.reinette.chatre@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Make bus clock frequency for vAPIC timer configurable | expand |
On Wed, Jun 12, 2024, Reinette Chatre wrote: > --- > .../selftests/kvm/include/x86_64/processor.h | 17 +++++++++++++++++ > .../selftests/kvm/lib/x86_64/processor.c | 11 +++++++++++ > 2 files changed, 28 insertions(+) > > diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h > index c0c7c1fe93f9..383a0f7fa9ef 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 uint32_t tsc_khz; This should be guest_tsc_khz, because it most definitely isn't guaranteed to be the host TSC frequency. And because it's global, we should try to avoid variable shadowing, e.g. tsc_scaling_sync.c also defines tsc_khz. Which, by the by, probably needs to be addressed, i.e. we should probably add a helper for setting KVM_SET_TSC_KHZ+guest_tsc_khz. I think it also makes sense to have this be a 64-bit value, even though KVM *internally* tracks a 32-bit value. That way we don't have to worry about casting to avoid truncation. > /* Forced emulation prefix, used to invoke the emulator unconditionally. */ > #define KVM_FEP "ud2; .byte 'k', 'v', 'm';" > @@ -816,6 +817,22 @@ 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(tsc_khz); > + cycles = tsc_khz / 1000 * usec; > + > + start = rdtsc(); > + for (;;) { > + now = rdtsc(); > + if (now - start >= cycles) > + break; > + cpu_relax(); Given that this is guest code, we should omit the PAUSE so that it doesn't trigger PLE exits, i.e. to make the delay as accurate as possible. Then this simply becomes: start = rdtsc(); do { now = rdtsc(); } while (now - start < cycles);
diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h index c0c7c1fe93f9..383a0f7fa9ef 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 uint32_t tsc_khz; /* Forced emulation prefix, used to invoke the emulator unconditionally. */ #define KVM_FEP "ud2; .byte 'k', 'v', 'm';" @@ -816,6 +817,22 @@ 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(tsc_khz); + cycles = tsc_khz / 1000 * usec; + + 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 594b061aef52..aaadda1ebcad 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; +uint32_t 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."); + tsc_khz = r; + sync_global_to_guest(vm, tsc_khz); } void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code)
Create udelay() utility for x86_64 tests to match udelay() available to ARM and RISC-V tests. Calibrate guest frequency using the KVM_GET_TSC_KHZ ioctl() and share it between host and guest with the new tsc_khz global variable. Signed-off-by: Reinette Chatre <reinette.chatre@intel.com> --- Changes v9: - Change tsc_kz type to uint32_t (was unsigned int). (Sean) - Change type used to store number of cycles to uint64_t (was unsigned long). (Sean) - Add GUEST_ASSERT() in udelay() used in guest to avoid risk of udelay() unexpectedly doing nothing if something went wrong during TSC frequency discovery. (Sean) - Use TEST_ASSERT() when checking for KVM_CAP_GET_TSC_KHZ. (Sean) - Use TEST_ASSERT() to enforce that discovery of TSC frequency must never fail. (Sean) Changes v8: - Use appropriate signed type to discover TSC freq from KVM. - Switch type used to store TSC frequency from unsigned long to unsigned int to match the type used by the kernel. Changes v7: - New patch --- .../selftests/kvm/include/x86_64/processor.h | 17 +++++++++++++++++ .../selftests/kvm/lib/x86_64/processor.c | 11 +++++++++++ 2 files changed, 28 insertions(+)