linux-kernel - Re: [PATCH] nvme-pci: Prevent mmio reads if pci channel offline

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Message-ID: <CAHk-=wjmjHyovjtzaq=HSegEpiO2SXWaYfJ6qsJrZhXg_YSx5g@mail.gmail.com>
Date:   Fri, 22 Feb 2019 13:28:42 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Jon Derrick <jonathan.derrick@...el.com>
Cc:     linux-nvme@...ts.infradead.org,
        Keith Busch <keith.busch@...el.com>, Jens Axboe <axboe@...com>,
        Christoph Hellwig <hch@....de>,
        Sagi Grimberg <sagi@...mberg.me>,
        Alex Gagniuc <alex_gagniuc@...lteam.com>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nvme-pci: Prevent mmio reads if pci channel offline

On Thu, Feb 21, 2019 at 5:07 PM Jon Derrick <jonathan.derrick@...el.com> wrote:
>
> Some platforms don't seem to easily tolerate non-posted mmio reads on
> lost (hot removed) devices. This has been noted in previous
> modifications to other layers where an mmio read to a lost device could
> cause an undesired firmware intervention [1][2].

This is broken, and whatever platform that requires this is broken.

This has absolutely nothing to do with nvme, and should not be handled
by a driver.

The platform code should be fixed.

What broken platform is this, and why is it causing problems?

None of this wishy-washy "some platforms". Name them, and let's get them fixed.

                 Linus