From: Stewart Hildebrand <stewart.hildebrand@amd.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>, xen-devel@lists.xenproject.org
Subject: Re: [PATCH v1 5/5] vpci: allow 32-bit BAR writes with memory decoding enabled
Date: Wed, 11 Jun 2025 16:22:16 -0400 [thread overview]
Message-ID: <e10959a7-4e72-4477-b8dd-b9d62e2a0ccf@amd.com> (raw)
In-Reply-To: <9ec5079f-9bc1-4843-a266-d74bf0556619@suse.com>
On 6/5/25 06:41, Jan Beulich wrote:
> On 31.05.2025 14:54, Stewart Hildebrand wrote:
>> Currently, Xen vPCI refuses BAR writes if the BAR is mapped in p2m. If
>> firmware initializes a 32-bit BAR to a bad address, Linux may try to
>> write a new address to the BAR without disabling memory decoding. Since
>> Xen refuses such writes, the BAR (and thus PCI device) will be
>> non-functional.
>
> Doing this for 32-bit BARs only, with not even an outline what to do about
> the same issue with 64-bit ones, seems like it won't buy us very much.
It buys us quite a lot: it means the difference between booting vs.
booting with degraded functionality or not booting at all with PVH dom0
on some platforms with certain PCI devices plugged in.
The plan for 64-bit BARs for now is to continue to refuse the write(s)
when the 64-bit BAR is mapped to avoid mapping half-updated BARs in p2m.
I'll add something to this effect to the commit message.
Also see https://gitlab.com/xen-project/xen/-/issues/197
next prev parent reply other threads:[~2025-06-11 20:22 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-31 12:53 [PATCH v1 0/5] vpci: allow 32-bit BAR writes with memory decoding enabled Stewart Hildebrand
2025-05-31 12:53 ` [PATCH v1 1/5] vpci: const-ify some pdev instances Stewart Hildebrand
2025-06-05 9:47 ` Roger Pau Monné
2025-06-11 19:28 ` Stewart Hildebrand
2025-07-07 16:27 ` Stewart Hildebrand
2025-05-31 12:54 ` [PATCH v1 2/5] vpci: rework error path in vpci_process_pending() Stewart Hildebrand
2025-06-05 9:53 ` Roger Pau Monné
2025-06-11 20:44 ` Stewart Hildebrand
2025-05-31 12:54 ` [PATCH v1 3/5] vpci: introduce map_bars() Stewart Hildebrand
2025-06-05 10:16 ` Roger Pau Monné
2025-06-11 19:55 ` Stewart Hildebrand
2025-05-31 12:54 ` [PATCH v1 4/5] vpci: use separate rangeset for BAR unmapping Stewart Hildebrand
2025-06-05 10:28 ` Roger Pau Monné
2025-06-05 10:38 ` Jan Beulich
2025-05-31 12:54 ` [PATCH v1 5/5] vpci: allow 32-bit BAR writes with memory decoding enabled Stewart Hildebrand
2025-06-05 10:41 ` Jan Beulich
2025-06-11 20:22 ` Stewart Hildebrand [this message]
2025-06-12 7:27 ` Jan Beulich
2025-06-12 7:32 ` Roger Pau Monné
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