linux-kernel - RE: [PATCH v2 0/3] More machine check recovery fixes

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Date:   Wed, 18 Aug 2021 16:14:38 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     Jue Wang <juew@...gle.com>, Ding Hui <dinghui@...gfor.com.cn>,
        "naoya.horiguchi@....com" <naoya.horiguchi@....com>,
        "osalvador@...e.de" <osalvador@...e.de>,
        "Song, Youquan" <youquan.song@...el.com>,
        "huangcun@...gfor.com.cn" <huangcun@...gfor.com.cn>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 0/3] More machine check recovery fixes

> Changes since v1:
> 1) Fix bug in kill_me_never() that forgot to clear p->mce_count so
>   repeated recovery in the same task would trigger the panic for
>	"Machine checks to different user pages"
>   [Note to Jue Wang ... this *might* be why your test that injects
>    two errors into the same buffer passed to a write(2) syscall
>    failed with this message]

I recreated Jue's specific test today with uncorrected errors in two
pages passed to a write(2) syscall.

	buf = alloc(2 pages);
	inject(buf + 0x440);
	inject*buf + 0x11c0);
	n = write(fd, buf, 8K);

Result was that the write returned 0x440 (i.e. bytes written up to the
first poison location).

-Tony