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powerpc/sched: Cleanup vcpu_is_preempted()

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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.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20231114071219.198222-1-aneesh.kumar@linux.ibm.com
This commit is contained in:
Aneesh Kumar K.V 2023-11-14 12:42:19 +05:30 committed by Michael Ellerman
parent a143892cb7
commit 6f4b7052da
1 changed files with 25 additions and 8 deletions
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33
arch/powerpc/include/asm/paravirt.h
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@ -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
#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;