linux-kernel - Re: [PATCH 11/15] KVM: selftests: Create VM with adjusted number of guest pages for perf tests

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Message-ID: <CANgfPd-D66s=78d8VbHHnpRLnWg134o+CApBVPRG2pUBSDR1Rw@mail.gmail.com>
Date:   Wed, 10 Feb 2021 17:32:53 -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 11/15] KVM: selftests: Create VM with adjusted number of
 guest pages for perf tests

On Wed, Feb 10, 2021 at 3:06 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Use the already computed guest_num_pages when creating the so called
> extra VM pages for a perf test, and add a comment explaining why the
> pages are allocated as extra pages.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

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

> ---
>  tools/testing/selftests/kvm/lib/perf_test_util.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
> index 982a86c8eeaa..9b0cfdf10772 100644
> --- a/tools/testing/selftests/kvm/lib/perf_test_util.c
> +++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
> @@ -71,9 +71,12 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus,
>         TEST_ASSERT(vcpu_memory_bytes % pta->guest_page_size == 0,
>                     "Guest memory size is not guest page size aligned.");
>
> -       vm = vm_create_with_vcpus(mode, vcpus,
> -                                 (vcpus * vcpu_memory_bytes) / pta->guest_page_size,
> -                                 0, guest_code, NULL);
> +       /*
> +        * Pass guest_num_pages to populate the page tables for test memory.
> +        * The memory is also added to memslot 0, but that's a benign side
> +        * effect as KVM allows aliasing HVAs in memslots.
> +        */
> +       vm = vm_create_with_vcpus(mode, vcpus, 0, guest_num_pages, guest_code, NULL);
>         pta->vm = vm;
>
>         /*
> --
> 2.30.0.478.g8a0d178c01-goog
>