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Date:   Fri, 22 Sep 2023 13:32:47 -0700
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Message-ID: <ZQ3573rbNQpbNf09@google.com>
Subject: Re: [RFC PATCH v2 0/6] KVM: gmem: Implement test cases for error_remove_page
From:   Sean Christopherson <seanjc@google.com>
To:     Isaku Yamahata <isaku.yamahata@linux.intel.com>
Cc:     isaku.yamahata@intel.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, isaku.yamahata@gmail.com,
        Michael Roth <michael.roth@amd.com>,
        Paolo Bonzini <pbonzini@redhat.com>, erdemaktas@google.com,
        Sagi Shahar <sagis@google.com>,
        David Matlack <dmatlack@google.com>,
        Kai Huang <kai.huang@intel.com>,
        Zhi Wang <zhi.wang.linux@gmail.com>, chen.bo@intel.com,
        linux-coco@lists.linux.dev,
        Chao Peng <chao.p.peng@linux.intel.com>,
        Ackerley Tng <ackerleytng@google.com>,
        Vishal Annapurve <vannapurve@google.com>,
        Yuan Yao <yuan.yao@linux.intel.com>,
        Jarkko Sakkinen <jarkko@kernel.org>,
        Xu Yilun <yilun.xu@intel.com>,
        Quentin Perret <qperret@google.com>, wei.w.wang@intel.com,
        Fuad Tabba <tabba@google.com>
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On Fri, Sep 22, 2023, Isaku Yamahata wrote:
> On Thu, Sep 21, 2023 at 01:29:59PM -0700,
> Sean Christopherson <seanjc@google.com> wrote:
> 
> > On Thu, Sep 21, 2023, isaku.yamahata@intel.com wrote:
> > > From: Isaku Yamahata <isaku.yamahata@intel.com>
> > > 
> > > This patch series is to implement test cases for the KVM gmem error_remove_page
> > > method.
> > > - Update punch hole method to truncate pages
> > > - Add a new ioctl KVM_GUEST_MEMORY_FAILURE to inject memory failure on
> > >   offset of gmem
> > 
> > Doh.  Please try to communicate what you're working on.  I was just about to hit
> > SEND on a series to fix the truncation bug, and to add a similar test.  I would
> > have happily punted that in your direction, but I had no idea that you were aware
> > of the bug[*], let alone working on a fix.  I could have explicitly stated that
> > I was going to fix the bug, but I thought that it was implied that I needed to
> > clean up my own mess.
> 
> Oops sorry.  Now I'm considering about machine check injection.
> i.e. somehow trigger kvm_machine_check() and its own test cases.

Unless we can't extend fadvise() for some reason, I think we should pursue
FADV_HWPOISION.  The enabling should be downright trivial, e.g. just implement
file_operations.fadvise() for guest_memfd, have it handle FADV_HWPOISON, and pass
everything else to generic_fadvise().

It'll basically be your ioctl() just without a dedicated ioctl().

At the very least, we should run the idea past the fs maintainers.