Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 17 Jan 2023 22:12:40 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Vishal Annapurve <vannapurve@google.com>
Cc:     x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, pbonzini@redhat.com,
        vkuznets@redhat.com, wanpengli@tencent.com, jmattson@google.com,
        joro@8bytes.org, tglx@linutronix.de, mingo@redhat.com,
        bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com,
        shuah@kernel.org, yang.zhong@intel.com, ricarkol@google.com,
        aaronlewis@google.com, wei.w.wang@intel.com,
        kirill.shutemov@linux.intel.com, corbet@lwn.net, hughd@google.com,
        jlayton@kernel.org, bfields@fieldses.org,
        akpm@linux-foundation.org, chao.p.peng@linux.intel.com,
        yu.c.zhang@linux.intel.com, jun.nakajima@intel.com,
        dave.hansen@intel.com, michael.roth@amd.com, qperret@google.com,
        steven.price@arm.com, ak@linux.intel.com, david@redhat.com,
        luto@kernel.org, vbabka@suse.cz, marcorr@google.com,
        erdemaktas@google.com, pgonda@google.com, nikunj@amd.com,
        diviness@google.com, maz@kernel.org, dmatlack@google.com,
        axelrasmussen@google.com, maciej.szmigiero@oracle.com,
        mizhang@google.com, bgardon@google.com, ackerleytng@google.com
Subject: Re: [V2 PATCH 5/6] KVM: selftests: Add get_free_huge_2m_pages
Message-ID: <Y8cdWKaZVXQFcO+i@google.com>
References: <20221205232341.4131240-1-vannapurve@google.com>
 <20221205232341.4131240-6-vannapurve@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20221205232341.4131240-6-vannapurve@google.com>
Precedence: bulk

On Mon, Dec 05, 2022, Vishal Annapurve wrote:
> Add an API to query free 2MB hugepages in the system.
> 
> Signed-off-by: Vishal Annapurve <vannapurve@google.com>
> ---
>  .../testing/selftests/kvm/include/test_util.h  |  1 +
>  tools/testing/selftests/kvm/lib/test_util.c    | 18 ++++++++++++++++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
> index aea80071f2b8..3d1cc215940a 100644
> --- a/tools/testing/selftests/kvm/include/test_util.h
> +++ b/tools/testing/selftests/kvm/include/test_util.h
> @@ -122,6 +122,7 @@ struct vm_mem_backing_src_alias {
>  bool thp_configured(void);
>  size_t get_trans_hugepagesz(void);
>  size_t get_def_hugetlb_pagesz(void);
> +size_t get_free_huge_2mb_pages(void);
>  const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i);
>  size_t get_backing_src_pagesz(uint32_t i);
>  bool is_backing_src_hugetlb(uint32_t i);
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index d33b98bfe8a3..745573023b57 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -162,6 +162,24 @@ size_t get_trans_hugepagesz(void)
>  	return size;
>  }
>  
> +size_t get_free_huge_2mb_pages(void)

I strongly prefer to follow the precedence set by other tests, which at this
point means defaulting to non-huge pages.  I do think we need to make it easier
and/or automatic to test hugepages, but I would like to tackle that problem
separately.  E.g. a kernel built without hugepage support will fail the fopen()
below.

> +{
> +	size_t free_pages;
> +	FILE *f;
> +	int ret;
> +
> +	f = fopen("/sys/kernel/mm/hugepages/hugepages-2048kB/free_hugepages", "r");
> +	TEST_ASSERT(f != NULL, "Error in opening hugepages-2048kB/free_hugepages");
> +
> +	do {
> +		ret = fscanf(f, "%ld", &free_pages);
> +	} while (errno == EINTR);
> +	TEST_ASSERT(ret < 1, "Error reading hugepages-2048kB/free_hugepages");
> +	fclose(f);
> +
> +	return free_pages;
> +}
> +
>  size_t get_def_hugetlb_pagesz(void)
>  {
>  	char buf[64];
> -- 
> 2.39.0.rc0.267.gcb52ba06e7-goog
>