linux-kernel - Re: [RFC PATCH v2 3/6] KVM: selftests: Add tests for punch hole on guest

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Date:   Thu, 21 Sep 2023 13:40:40 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     isaku.yamahata@...el.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        isaku.yamahata@...il.com, Michael Roth <michael.roth@....com>,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Kai Huang <kai.huang@...el.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, chen.bo@...el.com,
        linux-coco@...ts.linux.dev,
        Chao Peng <chao.p.peng@...ux.intel.com>,
        Ackerley Tng <ackerleytng@...gle.com>,
        Vishal Annapurve <vannapurve@...gle.com>,
        Yuan Yao <yuan.yao@...ux.intel.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Xu Yilun <yilun.xu@...el.com>,
        Quentin Perret <qperret@...gle.com>, wei.w.wang@...el.com,
        Fuad Tabba <tabba@...gle.com>
Subject: Re: [RFC PATCH v2 3/6] KVM: selftests: Add tests for punch hole on guest_memfd

On Thu, Sep 21, 2023, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> Punch hole implies the region is zeroed out. Add tests if the punched
> region has zero.
> Oppertunistically Remove unused member, pattern, in guest_run_test().

Heh, I didn't pretty much all the same stuff, except I opted to have
SET_ATTRIBUTE instead of FALLOCATE_ONLY, e.g. in case we end up with a test that's
wants a thrid flavor (or somehow neither?).

> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>  .../kvm/x86_64/private_mem_conversions_test.c | 26 ++++++++++++++-----
>  1 file changed, 20 insertions(+), 6 deletions(-)
> 

...

> @@ -156,6 +163,10 @@ static void guest_run_test(uint64_t base_gpa, bool do_fallocate)
>  
>  		if (size > PAGE_SIZE) {
>  			memset((void *)gpa, p2, PAGE_SIZE);
> +
> +			/* Test if punch hole results in zeroing page. */
> +			guest_punch_hole_private(gpa, PAGE_SIZE);
> +			memcmp_g(gpa, 0, PAGE_SIZE);

I added a dedicated sub-test to provide a bit more variety in the tests.  I highly
doubt my version will ever find a bug that isn't caught by this approach, but if
nothing else, it's nice to have a completely separate sub-test.