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From: Jane Chu <jane.chu@oracle.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: Borislav Petkov <bp@alien8.de>,
	"Luck, Tony" <tony.luck@intel.com>,
	Linux NVDIMM <nvdimm@lists.linux.dev>,
	Luis Chamberlain <mcgrof@suse.com>,
	"linux-cxl@vger.kernel.org" <linux-cxl@vger.kernel.org>
Subject: Re: [RFT PATCH] x86/pat: Fix set_mce_nospec() for pmem
Date: Tue, 30 Nov 2021 23:00:53 +0000	[thread overview]
Message-ID: <1d34f45c-2b6a-1f4d-71ff-715885f8f41a@oracle.com> (raw)
In-Reply-To: <CAPcyv4g4mEVDcUw2Ph0oMH1=ZQgCbnLx+ZdgoavyOQt+9q6aVw@mail.gmail.com>

On 11/24/2021 4:16 PM, Dan Williams wrote:
> On Thu, Nov 18, 2021 at 11:04 AM Jane Chu <jane.chu@oracle.com> wrote:
>>
>> On 11/13/2021 12:47 PM, Dan Williams wrote:
>> <snip>
<snip>
>>
>> Thanks Dan for taking the time elaborating so much details!
>>
>> After some amount of digging, I have a feel that we need to take
>> dax error handling in phases.
>>
>> Phase-1: the simplest dax_recovery_write on page granularity, along
>>            with fix to set poisoned page to 'NP', serialize
>>            dax_recovery_write threads.
> 
> You mean special case PAGE_SIZE overwrites when dax_direct_access()
> fails, but leave out the sub-page error handling and
> read-around-poison support?

Yes.
> 
> That makes sense to me. Incremental is good.

Thanks!
> 
>> Phase-2: provide dax_recovery_read support and hence shrink the error
>>            recovery granularity.  As ioremap returns __iomem pointer
>>            that is only allowed to be referenced with helpers like
>>            readl() which do not have a mc_safe variant, and I'm
>>            not sure whether there should be.  Also the synchronization
>>            between dax_recovery_read and dax_recovery_write threads.
> 
> You can just use memremap() like the driver does to drop the iomem annotation.

Okay, will investigate in phase 2.

> 
>> Phase-3: the hypervisor error-record keeping issue, suppose there is
>>            an issue, I'll need to figure out how to setup a test case.
>> Phase-4: the how-to-mitigate-MOVDIR64B-false-alarm issue.
> 
> My expectation is that CXL supports MOVDIR64B error clearing without
> needing to send the Clear Poison command. I think this can be phase3,
> phase4 is the more difficult question about how / if to coordinate
> with VMM poison tracking. Right now I don't see a choice but to make
> it paravirtualized.
> 
>>
>> Right now, it seems to me providing Phase-1 solution is urgent, to give
>> something that customers can rely on.
>>
>> How does this sound to you?
> 
> Sounds good.
> 

Thanks!
-jane

  reply	other threads:[~2021-11-30 23:01 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-07  1:01 [RFT PATCH] x86/pat: Fix set_mce_nospec() for pmem Dan Williams
2021-08-26 19:08 ` Dan Williams
2021-08-27  7:12   ` Jane Chu
2021-09-13 10:29 ` Borislav Petkov
2021-09-14 18:08   ` Dan Williams
2021-09-15 10:41     ` Borislav Petkov
2021-09-16 20:33       ` Dan Williams
2021-09-17 11:30         ` Borislav Petkov
2021-09-21  2:04           ` Dan Williams
2021-09-30 17:19             ` Borislav Petkov
2021-09-30 17:28               ` Luck, Tony
2021-09-30 19:30                 ` Borislav Petkov
2021-09-30 19:41                   ` Dan Williams
2021-09-30 19:44                   ` Luck, Tony
2021-09-30 20:01                     ` Borislav Petkov
2021-09-30 20:15                       ` Luck, Tony
2021-09-30 20:32                         ` Borislav Petkov
2021-09-30 20:39                           ` Dan Williams
2021-09-30 20:54                             ` Borislav Petkov
2021-09-30 21:05                               ` Dan Williams
2021-09-30 21:20                                 ` Borislav Petkov
2021-09-30 21:41                                   ` Dan Williams
2021-09-30 22:35                                     ` Borislav Petkov
2021-09-30 22:44                                       ` Dan Williams
2021-10-01 10:41                                         ` Borislav Petkov
2021-10-01  0:43                                       ` Jane Chu
2021-10-01  2:02                                         ` Dan Williams
2021-10-01 10:50                                           ` Borislav Petkov
2021-10-01 16:52                                             ` Dan Williams
2021-10-01 18:11                                               ` Borislav Petkov
2021-10-01 18:29                                                 ` Dan Williams
2021-10-02 10:17                                                   ` Borislav Petkov
2021-11-11  0:06                                                     ` Jane Chu
2021-11-12  0:30                                                       ` Jane Chu
2021-11-12  0:51                                                         ` Dan Williams
2021-11-12 17:57                                                           ` Jane Chu
2021-11-12 19:24                                                             ` Dan Williams
2021-11-12 22:35                                                               ` Jane Chu
2021-11-12 22:50                                                                 ` Jane Chu
2021-11-12 23:08                                                                 ` Dan Williams
2021-11-13  5:50                                                                   ` Jane Chu
2021-11-13 20:47                                                                     ` Dan Williams
2021-11-18 19:03                                                                       ` Jane Chu
2021-11-25  0:16                                                                         ` Dan Williams
2021-11-30 23:00                                                                           ` Jane Chu [this message]
2021-09-30 18:15         ` Jane Chu
2021-09-30 19:11           ` Dan Williams
2021-09-30 21:23             ` Jane Chu

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