linux-kernel - Re: [RFC PATCH v2 0/6] KVM: gmem: Implement test cases for error_remove

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Date:   Fri, 22 Sep 2023 13:32:47 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Isaku Yamahata <isaku.yamahata@...ux.intel.com>
Cc:     isaku.yamahata@...el.com, 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 0/6] KVM: gmem: Implement test cases for error_remove_page

On Fri, Sep 22, 2023, Isaku Yamahata wrote:
> On Thu, Sep 21, 2023 at 01:29:59PM -0700,
> Sean Christopherson <seanjc@...gle.com> wrote:
> 
> > On Thu, Sep 21, 2023, isaku.yamahata@...el.com wrote:
> > > From: Isaku Yamahata <isaku.yamahata@...el.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.