linux-kernel - Re: [PATCH v4 2/2] mm,hwpoison: send SIGBUS when the page has already been poisoned

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Message-ID: <20210510083155.GB3504859@hori.linux.bs1.fc.nec.co.jp>
Date:   Mon, 10 May 2021 08:31:57 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Aili Yao <yaoaili@...gsoft.com>
CC:     Naoya Horiguchi <nao.horiguchi@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Tony Luck <tony.luck@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>, Jue Wang <juew@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "yaoaili126@...il.com" <yaoaili126@...il.com>
Subject: Re: [PATCH v4 2/2] mm,hwpoison: send SIGBUS when the page has already
 been poisoned

On Mon, May 10, 2021 at 04:00:21PM +0800, Aili Yao wrote:
> On Mon, 10 May 2021 07:21:28 +0000
> HORIGUCHI NAOYA(堀口　直也) <naoya.horiguchi@....com> wrote:
> 
> > On Fri, May 07, 2021 at 05:38:52PM +0800, Aili Yao wrote:
> > > On Tue, 27 Apr 2021 15:29:53 +0900
...
> > > And I think the virtual address along SIGBUS is not mean to backtrace the code, it just want to tell where the error memory is, for multi pte
> > > entry, one virtual address for the same physical page is not enough?
> > > 
> > > Compare this patch with my RFC patch, difference:
> > > 1.This patch will just fix the race issue's invalid virtual address. while my RFC patch will cover all the error case for recovery;
> > > 2.For multi entry, this patch will do one force_sig with no other infomation, But the RFC patch will take one possible right address, I don't know which one is better.
> > > 
> > > And if this multi pte entry is one real issue, it seems the normal recovey work will aslo trigger this, would it be better to fix that first?  
> > 
> > Assuming that your RFC is https://lore.kernel.org/lkml/20210317162304.58ff188c@alex-virtual-machine/,
> > it simply uses the first-found virtual address.  I start thinking that this
> > approach could be fine.  And it's easy to change the patch with this approach.
> > I have no preference, so if you like, I switch to the "first-found" approach.
> 
> Hi Naoya:
>   Thanks for your reply!
>   Yes, you can change to that RFC approach, but there may be some un-indentified issuees, and need more considerations though.
>   And there may be other method to address this, you can also dig into that, get it realized and posted.
>   I am OK with any option.
>   But for here, From the beginning, I thinks the invalid address issue and race issue are two different issues, may have some
> relationship but still two issues in my mind.
>   whould you please seperate this series patches into three again?

OK, I'll do it.
Maybe that's helpful if we consider to send some part of the series to stable.

- Naoya