From: Jan Beulich <jbeulich@suse.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: "Bjorn Helgaas" <bhelgaas@google.com>,
"Jürgen Groß" <jgross@suse.com>,
"Roger Pau Monné" <roger.pau@citrix.com>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
xen-devel <xen-devel@lists.xenproject.org>,
linux-kernel@vger.kernel.org, regressions@lists.linux.dev,
"Felix Fietkau" <nbd@nbd.name>,
"Lorenzo Bianconi" <lorenzo@kernel.org>,
"Ryder Lee" <ryder.lee@mediatek.com>,
linux-pci@vger.kernel.org,
"Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
Subject: Re: Config space access to Mediatek MT7922 doesn't work after device reset in Xen PV dom0 (regression, Linux 6.12)
Date: Wed, 29 Jan 2025 14:52:33 +0100 [thread overview]
Message-ID: <841e1793-4635-4f06-b0c9-37530215c08b@suse.com> (raw)
In-Reply-To: <20250129133252.GA451735@bhelgaas>
On 29.01.2025 14:32, Bjorn Helgaas wrote:
> On Wed, Jan 29, 2025 at 04:47:28AM +0100, Marek Marczykowski-Górecki wrote:
>> On Tue, Jan 28, 2025 at 09:40:18PM -0600, Bjorn Helgaas wrote:
>>> I guess the code at [2] is running in user mode and uses Linux
>>> syscalls for config access? Is it straceable?
>>
>> Nope, it's running as the hypervisor and mediates Linux's access to the
>> hardware. In fact, Linux PV kernel (which dom0 is by default under Xen)
>> is running in ring 3...
>>
>> But I can add some more logging there.
>
> So I guess the hypervisor performs the config access on behalf of the
> Linux PV kernel? Obviously Linux thinks CRS/RRS SV is enabled, but I
> suppose all the lspci output is similarly based on whatever the
> hypervisor does, so how do we know the actual hardware config?
The hypervisor only intercepts config space writes; reads, particularly
when going via mmcfg, ought to be unaffected, and hence what lspci shows
should be "the actual hardware config".
Jan
next prev parent reply other threads:[~2025-01-29 13:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Z5mOKQUrgeF_r6te@mail-itl>
2025-01-29 3:03 ` Config space access to Mediatek MT7922 doesn't work after device reset in Xen PV dom0 (regression, Linux 6.12) Bjorn Helgaas
2025-01-29 3:22 ` Marek Marczykowski-Górecki
2025-01-29 3:40 ` Bjorn Helgaas
2025-01-29 3:47 ` Marek Marczykowski-Górecki
2025-01-29 13:32 ` Bjorn Helgaas
2025-01-29 13:52 ` Jan Beulich [this message]
2025-01-29 14:50 ` Bjorn Helgaas
2025-01-29 9:17 ` Jan Beulich
2025-01-29 11:53 ` Marek Marczykowski-Górecki
2025-01-29 12:49 ` Jan Beulich
2025-01-29 13:28 ` Bjorn Helgaas
2025-01-29 13:54 ` Jan Beulich
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