On 11/14/23 12:42 PM, Aneesh Kumar K.V wrote:
> No functional change in this patch. A helper is added to find if
> vcpu is dispatched by hypervisor. Use that instead of opencoding.
> Also clarify some of the comments.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com>
> ---
> arch/powerpc/include/asm/paravirt.h | 33 ++++++++++++++++++++++-------
> 1 file changed, 25 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/paravirt.h
> b/arch/powerpc/include/asm/paravirt.h
> index ac4279208d63..b78b82d66057 100644
> --- a/arch/powerpc/include/asm/paravirt.h
> +++ b/arch/powerpc/include/asm/paravirt.h
> @@ -76,6 +76,17 @@ static inline bool is_vcpu_idle(int vcpu)
> {
> return lppaca_of(vcpu).idle;
> }
> +
> +static inline bool vcpu_is_dispatched(int vcpu)
> +{
> + /*
> + * This is the yield_count. An "odd" value (low bit on) means that
> + * the processor is yielded (either because of an OS yield or a
> + * hypervisor preempt). An even value implies that the processor is
> + * currently executing.
> + */
> + return (!(yield_count_of(vcpu) & 1));
> +}
> #else
> static inline bool is_shared_processor(void)
> {
> @@ -109,6 +120,10 @@ static inline bool is_vcpu_idle(int vcpu)
> {
> return false;
> }
> +static inline bool vcpu_is_dispatched(int vcpu)
> +{
> + return true;
> +}
> #endif
>
Similar code can be changed in lib/qspinlock.c and lib/locks.c as well.
> #define vcpu_is_preempted vcpu_is_preempted
> @@ -134,12 +149,12 @@ static inline bool vcpu_is_preempted(int cpu)
> * If the hypervisor has dispatched the target CPU on a physical
> * processor, then the target CPU is definitely not preempted.
> */
> - if (!(yield_count_of(cpu) & 1))
> + if (vcpu_is_dispatched(cpu))
> return false;
>
> /*
> - * If the target CPU has yielded to Hypervisor but OS has not
> - * requested idle then the target CPU is definitely preempted.
> + * if the target CPU is not dispatched and the guest OS
> + * has not marked the CPU idle, then it is hypervisor preempted.
> */
> if (!is_vcpu_idle(cpu))
> return true;
> @@ -166,7 +181,7 @@ static inline bool vcpu_is_preempted(int cpu)
>
> /*
> * The PowerVM hypervisor dispatches VMs on a whole core
> - * basis. So we know that a thread sibling of the local CPU
> + * basis. So we know that a thread sibling of the executing CPU
> * cannot have been preempted by the hypervisor, even if it
> * has called H_CONFER, which will set the yield bit.
> */
> @@ -174,15 +189,17 @@ static inline bool vcpu_is_preempted(int cpu)
> return false;
>
> /*
> - * If any of the threads of the target CPU's core are not
> - * preempted or ceded, then consider target CPU to be
> - * non-preempted.
> + * The specific target CPU was marked by guest OS as idle, but
> + * then also check all other cpus in the core for PowerVM
> + * because it does core scheduling and one of the vcpu
> + * of the core getting preempted by hypervisor implies
> + * other vcpus can also be considered preempted.
> */
> first_cpu = cpu_first_thread_sibling(cpu);
> for (i = first_cpu; i < first_cpu + threads_per_core; i++) {
> if (i == cpu)
> continue;
> - if (!(yield_count_of(i) & 1))
> + if (vcpu_is_dispatched(i))
> return false;
> if (!is_vcpu_idle(i))
> return true;
