linux-kernel - Re: [PATCH v4 3/3] KVM: selftests: Test behavior of KVM_X86_DISABLE_EXITS

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Message-ID: <aFsltm1Ce24OA0nd@google.com>
Date: Tue, 24 Jun 2025 15:24:54 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Jim Mattson <jmattson@...gle.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v4 3/3] KVM: selftests: Test behavior of KVM_X86_DISABLE_EXITS_APERFMPERF

On Fri, May 30, 2025, Jim Mattson wrote:
> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index 5649cf2f40e8..b6c707ab92d7 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -10,6 +10,7 @@
>  #include "ucall_common.h"
>  
>  #include <assert.h>
> +#include <pthread.h>
>  #include <sched.h>
>  #include <sys/mman.h>
>  #include <sys/resource.h>
> @@ -2321,3 +2322,19 @@ bool vm_is_gpa_protected(struct kvm_vm *vm, vm_paddr_t paddr)
>  	pg = paddr >> vm->page_shift;
>  	return sparsebit_is_set(region->protected_phy_pages, pg);
>  }
> +
> +int pin_task_to_one_cpu(void)
> +{
> +	int cpu = sched_getcpu();
> +	cpu_set_t cpuset;
> +	int rc;
> +
> +	CPU_ZERO(&cpuset);
> +	CPU_SET(cpu, &cpuset);
> +
> +	rc = pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset);
> +	TEST_ASSERT(rc == 0, "%s: Can't set thread affinity", __func__);
> +
> +	return cpu;
> +}

There's already kvm_pin_this_task_to_pcpu(), which is *almost* what is needed
here.  I'll slot in a patch in v5 to expand that into a set of APIs, along with
a patch to convert the low hanging fruit (arch_timer tests).