linux-kernel - Re: [PATCH 2/2] PCI: vmd: Fix shadow offsets to reflect spec changes

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Message-ID: <20190917163716.GA9715@e121166-lin.cambridge.arm.com>
Date:   Tue, 17 Sep 2019 17:37:24 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     "Derrick, Jonathan" <jonathan.derrick@...el.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Busch, Keith" <keith.busch@...el.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "helgaas@...nel.org" <helgaas@...nel.org>
Subject: Re: [PATCH 2/2] PCI: vmd: Fix shadow offsets to reflect spec changes

On Tue, Sep 17, 2019 at 03:51:39PM +0000, Derrick, Jonathan wrote:

[...]

> Sorry for the confusion.
> 
> These changes only affect systems with VMD devices with 8086:28C0
> device IDs, but these won't be production hardware for some time.
> 
> Systems with VMD devices exist in the wild with 8086:201D device IDs.
> These don't support the guest passthrough mode and this code won't
> break anything with them. Additionally, patch 1/2 (bus numbering) only
> affects 8086:28C0.
> 
> So on existing HW, these patches won't affect anything

It is me who created confusion, apologies. I read the code properly and
I understand that both patches are fixes for HW that is still not
available (and they can't create an issue with current kernel because
HAS_MEMBAR_SHADOW and HAS_BUS_RESTRICTIONS features are not implemented
on 8086:201D), we should take these patches and trickle them to stable
kernels as soon as possible so that when HW _is_ available mainline and
stable kernels are fixed.

Correct ?

Lorenzo