linux-kernel - RE: [RFC PATCH] mmc: core: Disable REQ_FUA if the eMMC supports an internal cache

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 3 Mar 2023 09:39:42 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Bean Huo <huobean@...il.com>, Ulf Hansson <ulf.hansson@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>
CC:     Wenchao Chen <wenchao.chen666@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Christian Lohle <cloehle@...erstone.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH] mmc: core: Disable REQ_FUA if the eMMC supports an
 internal cache

> On 02.03.23 3:43 PM, Ulf Hansson wrote:
> > REQ_FUA is in general supported for eMMC cards, which translates into
> > so called "reliable writes". To support these write operations, the
> > CMD23 (MMC_CAP_CMD23), needs to be supported by the mmc host too,
> > which is common but not always the case.
> >
> > For some eMMC devices, it has been reported that reliable writes are
> > quite costly, leading to performance degradations.
> >
> > In a way to improve the situation, let's avoid announcing REQ_FUA
> > support if the eMMC supports an internal cache, as that allows us to
> > rely solely on flush-requests (REQ_OP_FLUSH) instead, which seems to be a
> lot cheaper.
> > Note that, those mmc hosts that lacks CMD23 support are already using
> > this type of configuration, whatever that could mean.
> >
> > Reported-by: Wenchao Chen<wenchao.chen666@...il.com>
> > Signed-off-by: Ulf Hansson<ulf.hansson@...aro.org>
> Acked-by: Bean Huo <beanhuo@...ron.com>
Acked-by: Avri Altman <avri.altman@....com>

Another option might be, allowing to report "broken_fua",
should the platform owner chooses to, much like scsi does per sdev.

Thanks,
Avri