| Message ID | 20210901211412.4171835-8-rananta@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: selftests: Introduce arch_timer selftest | expand |
On Wed, Sep 01, 2021 at 09:14:07PM +0000, Raghavendra Rao Ananta wrote: > At times, such as when in the interrupt handler, the guest wants to > get the vCPU-id that it's running on. As a result, introduce > get_vcpuid() that parses the MPIDR_EL1 and returns the vcpuid to the > requested caller. > > Signed-off-by: Raghavendra Rao Ananta <rananta@google.com> > --- > .../selftests/kvm/include/aarch64/processor.h | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/tools/testing/selftests/kvm/include/aarch64/processor.h b/tools/testing/selftests/kvm/include/aarch64/processor.h > index c35bb7b8e870..8b372cd427da 100644 > --- a/tools/testing/selftests/kvm/include/aarch64/processor.h > +++ b/tools/testing/selftests/kvm/include/aarch64/processor.h > @@ -251,4 +251,23 @@ static inline void local_irq_disable(void) > asm volatile("msr daifset, #3" : : : "memory"); > } > > +#define MPIDR_LEVEL_BITS 8 > +#define MPIDR_LEVEL_SHIFT(level) (MPIDR_LEVEL_BITS * level) > +#define MPIDR_LEVEL_MASK ((1 << MPIDR_LEVEL_BITS) - 1) > +#define MPIDR_AFFINITY_LEVEL(mpidr, level) \ > + ((mpidr >> MPIDR_LEVEL_SHIFT(level)) & MPIDR_LEVEL_MASK) > + > +static inline uint32_t get_vcpuid(void) > +{ > + uint32_t vcpuid = 0; > + uint64_t mpidr = read_sysreg(mpidr_el1); > + > + /* KVM limits only 16 vCPUs at level 0 */ > + vcpuid = mpidr & 0x0f; > + vcpuid |= MPIDR_AFFINITY_LEVEL(mpidr, 1) << 4; > + vcpuid |= MPIDR_AFFINITY_LEVEL(mpidr, 2) << 12; > + > + return vcpuid; > +} Are we guaranteed that KVM will always compose vCPU IDs the same way? I do not believe this is guaranteed ABI. For the base case, you could pass the vCPU ID as an arg to the guest function. I do agree that finding the vCPU ID is a bit more challenging in an interrupt context. Maybe use a ucall to ask userspace? But of course, every test implements its own run loop, so its yet another case that tests need to handle. Or, you could allocate an array at runtime of length KVM_CAP_MAX_VCPUS (use the KVM_CHECK_EXTENSION ioctl to get the value). Once all vCPUs are instantiated, iterate over them from userspace to populate the {MPIDR, VCPU_ID} map. You'd need to guarantee that callers initialize the vGIC *after* adding vCPUs to the guest. -- Thanks, Oliver > #endif /* SELFTEST_KVM_PROCESSOR_H */ > -- > 2.33.0.153.gba50c8fa24-goog >
On Wed, Sep 01, 2021 at 11:48:12PM +0000, Oliver Upton wrote: > On Wed, Sep 01, 2021 at 09:14:07PM +0000, Raghavendra Rao Ananta wrote: > > At times, such as when in the interrupt handler, the guest wants to > > get the vCPU-id that it's running on. As a result, introduce > > get_vcpuid() that parses the MPIDR_EL1 and returns the vcpuid to the > > requested caller. > > > > Signed-off-by: Raghavendra Rao Ananta <rananta@google.com> > > --- > > .../selftests/kvm/include/aarch64/processor.h | 19 +++++++++++++++++++ > > 1 file changed, 19 insertions(+) > > > > diff --git a/tools/testing/selftests/kvm/include/aarch64/processor.h b/tools/testing/selftests/kvm/include/aarch64/processor.h > > index c35bb7b8e870..8b372cd427da 100644 > > --- a/tools/testing/selftests/kvm/include/aarch64/processor.h > > +++ b/tools/testing/selftests/kvm/include/aarch64/processor.h > > @@ -251,4 +251,23 @@ static inline void local_irq_disable(void) > > asm volatile("msr daifset, #3" : : : "memory"); > > } > > > > +#define MPIDR_LEVEL_BITS 8 > > +#define MPIDR_LEVEL_SHIFT(level) (MPIDR_LEVEL_BITS * level) > > +#define MPIDR_LEVEL_MASK ((1 << MPIDR_LEVEL_BITS) - 1) > > +#define MPIDR_AFFINITY_LEVEL(mpidr, level) \ > > + ((mpidr >> MPIDR_LEVEL_SHIFT(level)) & MPIDR_LEVEL_MASK) > > + > > +static inline uint32_t get_vcpuid(void) > > +{ > > + uint32_t vcpuid = 0; > > + uint64_t mpidr = read_sysreg(mpidr_el1); > > + > > + /* KVM limits only 16 vCPUs at level 0 */ > > + vcpuid = mpidr & 0x0f; > > + vcpuid |= MPIDR_AFFINITY_LEVEL(mpidr, 1) << 4; > > + vcpuid |= MPIDR_AFFINITY_LEVEL(mpidr, 2) << 12; > > + > > + return vcpuid; > > +} > > Are we guaranteed that KVM will always compose vCPU IDs the same way? I > do not believe this is guaranteed ABI. I don't believe we are. At least in QEMU we take pains to avoid that assumption. > > For the base case, you could pass the vCPU ID as an arg to the guest > function. > > I do agree that finding the vCPU ID is a bit more challenging in an > interrupt context. Maybe use a ucall to ask userspace? But of course, > every test implements its own run loop, so its yet another case that > tests need to handle. > > Or, you could allocate an array at runtime of length KVM_CAP_MAX_VCPUS > (use the KVM_CHECK_EXTENSION ioctl to get the value). Once all vCPUs are > instantiated, iterate over them from userspace to populate the {MPIDR, > VCPU_ID} map. You'd need to guarantee that callers initialize the vGIC > *after* adding vCPUs to the guest. I agree with this approach. It may even make sense to create a common function that returns a {cpu_id,vcpu_index} map for other tests to use. Thanks, drew > > -- > Thanks, > Oliver > > > #endif /* SELFTEST_KVM_PROCESSOR_H */ > > -- > > 2.33.0.153.gba50c8fa24-goog > > > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm >
On Thu, Sep 2, 2021 at 5:37 AM Andrew Jones <drjones@redhat.com> wrote: > > On Wed, Sep 01, 2021 at 11:48:12PM +0000, Oliver Upton wrote: > > On Wed, Sep 01, 2021 at 09:14:07PM +0000, Raghavendra Rao Ananta wrote: > > > At times, such as when in the interrupt handler, the guest wants to > > > get the vCPU-id that it's running on. As a result, introduce > > > get_vcpuid() that parses the MPIDR_EL1 and returns the vcpuid to the > > > requested caller. > > > > > > Signed-off-by: Raghavendra Rao Ananta <rananta@google.com> > > > --- > > > .../selftests/kvm/include/aarch64/processor.h | 19 +++++++++++++++++++ > > > 1 file changed, 19 insertions(+) > > > > > > diff --git a/tools/testing/selftests/kvm/include/aarch64/processor.h b/tools/testing/selftests/kvm/include/aarch64/processor.h > > > index c35bb7b8e870..8b372cd427da 100644 > > > --- a/tools/testing/selftests/kvm/include/aarch64/processor.h > > > +++ b/tools/testing/selftests/kvm/include/aarch64/processor.h > > > @@ -251,4 +251,23 @@ static inline void local_irq_disable(void) > > > asm volatile("msr daifset, #3" : : : "memory"); > > > } > > > > > > +#define MPIDR_LEVEL_BITS 8 > > > +#define MPIDR_LEVEL_SHIFT(level) (MPIDR_LEVEL_BITS * level) > > > +#define MPIDR_LEVEL_MASK ((1 << MPIDR_LEVEL_BITS) - 1) > > > +#define MPIDR_AFFINITY_LEVEL(mpidr, level) \ > > > + ((mpidr >> MPIDR_LEVEL_SHIFT(level)) & MPIDR_LEVEL_MASK) > > > + > > > +static inline uint32_t get_vcpuid(void) > > > +{ > > > + uint32_t vcpuid = 0; > > > + uint64_t mpidr = read_sysreg(mpidr_el1); > > > + > > > + /* KVM limits only 16 vCPUs at level 0 */ > > > + vcpuid = mpidr & 0x0f; > > > + vcpuid |= MPIDR_AFFINITY_LEVEL(mpidr, 1) << 4; > > > + vcpuid |= MPIDR_AFFINITY_LEVEL(mpidr, 2) << 12; > > > + > > > + return vcpuid; > > > +} > > > > Are we guaranteed that KVM will always compose vCPU IDs the same way? I > > do not believe this is guaranteed ABI. > > I don't believe we are. At least in QEMU we take pains to avoid that > assumption. > > > > > For the base case, you could pass the vCPU ID as an arg to the guest > > function. > > > > I do agree that finding the vCPU ID is a bit more challenging in an > > interrupt context. Maybe use a ucall to ask userspace? But of course, > > every test implements its own run loop, so its yet another case that > > tests need to handle. > > > > Or, you could allocate an array at runtime of length KVM_CAP_MAX_VCPUS > > (use the KVM_CHECK_EXTENSION ioctl to get the value). Once all vCPUs are > > instantiated, iterate over them from userspace to populate the {MPIDR, > > VCPU_ID} map. You'd need to guarantee that callers initialize the vGIC > > *after* adding vCPUs to the guest. > > I agree with this approach. It may even make sense to create a common > function that returns a {cpu_id,vcpu_index} map for other tests to use. > Interesting idea. I'll look into this. Regards, Raghavendra > Thanks, > drew > > > > > -- > > Thanks, > > Oliver > > > > > #endif /* SELFTEST_KVM_PROCESSOR_H */ > > > -- > > > 2.33.0.153.gba50c8fa24-goog > > > > > _______________________________________________ > > kvmarm mailing list > > kvmarm@lists.cs.columbia.edu > > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm > > >
diff --git a/tools/testing/selftests/kvm/include/aarch64/processor.h b/tools/testing/selftests/kvm/include/aarch64/processor.h index c35bb7b8e870..8b372cd427da 100644 --- a/tools/testing/selftests/kvm/include/aarch64/processor.h +++ b/tools/testing/selftests/kvm/include/aarch64/processor.h @@ -251,4 +251,23 @@ static inline void local_irq_disable(void) asm volatile("msr daifset, #3" : : : "memory"); } +#define MPIDR_LEVEL_BITS 8 +#define MPIDR_LEVEL_SHIFT(level) (MPIDR_LEVEL_BITS * level) +#define MPIDR_LEVEL_MASK ((1 << MPIDR_LEVEL_BITS) - 1) +#define MPIDR_AFFINITY_LEVEL(mpidr, level) \ + ((mpidr >> MPIDR_LEVEL_SHIFT(level)) & MPIDR_LEVEL_MASK) + +static inline uint32_t get_vcpuid(void) +{ + uint32_t vcpuid = 0; + uint64_t mpidr = read_sysreg(mpidr_el1); + + /* KVM limits only 16 vCPUs at level 0 */ + vcpuid = mpidr & 0x0f; + vcpuid |= MPIDR_AFFINITY_LEVEL(mpidr, 1) << 4; + vcpuid |= MPIDR_AFFINITY_LEVEL(mpidr, 2) << 12; + + return vcpuid; +} + #endif /* SELFTEST_KVM_PROCESSOR_H */
At times, such as when in the interrupt handler, the guest wants to get the vCPU-id that it's running on. As a result, introduce get_vcpuid() that parses the MPIDR_EL1 and returns the vcpuid to the requested caller. Signed-off-by: Raghavendra Rao Ananta <rananta@google.com> --- .../selftests/kvm/include/aarch64/processor.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)