linux-kernel - Re: [PATCH 08/15] KVM: selftests: Use perf util's per-vCPU GPA/pages in demand paging test

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Date:   Wed, 10 Feb 2021 17:23:42 -0800
From:   Ben Gardon <bgardon@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Yanan Wang <wangyanan55@...wei.com>,
        Andrew Jones <drjones@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        Aaron Lewis <aaronlewis@...gle.com>
Subject: Re: [PATCH 08/15] KVM: selftests: Use perf util's per-vCPU GPA/pages
 in demand paging test

On Wed, Feb 10, 2021 at 3:06 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Grab the per-vCPU GPA and number of pages from perf_util in the demand
> paging test instead of duplicating perf_util's calculations.
>
> Note, this may or may not result in a functional change.  It's not clear
> that the test's calculations are guaranteed to yield the same value as
> perf_util, e.g. if guest_percpu_mem_size != vcpu_args->pages.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Ben Gardon <bgardon@...gle.com>

> ---
>  .../selftests/kvm/demand_paging_test.c        | 20 +++++--------------
>  1 file changed, 5 insertions(+), 15 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
> index 5f7a229c3af1..0cbf111e6c21 100644
> --- a/tools/testing/selftests/kvm/demand_paging_test.c
> +++ b/tools/testing/selftests/kvm/demand_paging_test.c
> @@ -294,24 +294,13 @@ static void run_test(enum vm_guest_mode mode, void *arg)
>                 TEST_ASSERT(pipefds, "Unable to allocate memory for pipefd");
>
>                 for (vcpu_id = 0; vcpu_id < nr_vcpus; vcpu_id++) {
> -                       vm_paddr_t vcpu_gpa;
> +                       struct perf_test_vcpu_args *vcpu_args;
>                         void *vcpu_hva;
> -                       uint64_t vcpu_mem_size;
>
> -
> -                       if (p->partition_vcpu_memory_access) {
> -                               vcpu_gpa = guest_test_phys_mem +
> -                                          (vcpu_id * guest_percpu_mem_size);
> -                               vcpu_mem_size = guest_percpu_mem_size;
> -                       } else {
> -                               vcpu_gpa = guest_test_phys_mem;
> -                               vcpu_mem_size = guest_percpu_mem_size * nr_vcpus;
> -                       }
> -                       PER_VCPU_DEBUG("Added VCPU %d with test mem gpa [%lx, %lx)\n",
> -                                      vcpu_id, vcpu_gpa, vcpu_gpa + vcpu_mem_size);
> +                       vcpu_args = &perf_test_args.vcpu_args[vcpu_id];
>
>                         /* Cache the HVA pointer of the region */
> -                       vcpu_hva = addr_gpa2hva(vm, vcpu_gpa);
> +                       vcpu_hva = addr_gpa2hva(vm, vcpu_args->gpa);
>
>                         /*
>                          * Set up user fault fd to handle demand paging
> @@ -325,7 +314,8 @@ static void run_test(enum vm_guest_mode mode, void *arg)
>                                                 &uffd_handler_threads[vcpu_id],
>                                                 pipefds[vcpu_id * 2],
>                                                 p->uffd_delay, &uffd_args[vcpu_id],
> -                                               vcpu_hva, vcpu_mem_size);
> +                                               vcpu_hva,
> +                                               vcpu_args->pages * perf_test_args.guest_page_size);
>                         if (r < 0)
>                                 exit(-r);
>                 }
> --
> 2.30.0.478.g8a0d178c01-goog
>