From: Bjorn Helgaas <helgaas@kernel.org>
To: "Pali Rohár" <pali@kernel.org>
Cc: "Martin Mareš" <mj@ucw.cz>, "Krzysztof Wilczyński" <kw@linux.com>,
"Matthew Wilcox" <willy@infradead.org>,
linux-pci@vger.kernel.org
Subject: Re: IORESOURCE_WINDOW for PCI-to-PCI bridges
Date: Tue, 15 Nov 2022 16:15:02 -0600 [thread overview]
Message-ID: <20221115221502.GA755872@bhelgaas> (raw)
In-Reply-To: <20221111214816.65fi63ffgvr6nbj2@pali>
On Fri, Nov 11, 2022 at 10:48:16PM +0100, Pali Rohár wrote:
> On Friday 11 November 2022 15:05:55 Bjorn Helgaas wrote:
> > On Fri, Nov 11, 2022 at 09:09:45PM +0100, Pali Rohár wrote:
> > > On Thursday 20 January 2022 15:02:12 Bjorn Helgaas wrote:
> > > > On Thu, Jan 20, 2022 at 09:45:05PM +0100, Pali Rohár wrote:
> >
> > [trimmed material; beginning of thread is at
> > https://lore.kernel.org/r/20211220155448.1233-3-pali@kernel.org]
> >
> > > > > Meanwhile I found out that in linux/ioport.h file is IORESOURCE_WINDOW
> > > > > constant with comment /* forwarded by bridge */
> > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/ioport.h?h=v5.15#n56
> > > > >
> > > > > But apparently it is not set for resources behind PCI bridges and
> > > > > therefore it is not available in column of "resources" sysfs file.
> > > > >
> > > > > So maybe instead of adding new sysfs files, it would be better way to
> > > > > implement this flag and export it in flags column of "resources" file
> > > > > for every row which belongs to resources behind bridges?
> > > >
> > > > I looked at that, too. Today we only set IORESOURCE_WINDOW for host
> > > > bridge windows. Maybe it could be set for PCI-to-PCI bridge windows,
> > > > too. Would have to audit users to make sure it wouldn't break
> > > > anything.
> > >
> > > Hello Bjorn, I would like to remind this older issue. Did you have a time
> > > to audit usage of IORESOURCE_WINDOW? Some flag for resource forwarding
> > > windows in PCI-to-PCI bridges would really help userspace application to
> > > distinguish between IO/MEM BARs an IO/MEM forwarding windows.
> >
> > I had forgotten all about this issue. IIUC, the ultimate goal here
> > is to help lspci distinguish between an I/O window that's disabled and
> > one that's enabled at [io 0x0000-0x0fff].
> >
> > I have not done the research to see whether it would be safe to set
> > IORESOURCE_WINDOW for PCI-to-PCI bridge windows. I'm sorry if I left
> > the impression that I intended to do that. I would welcome your help
> > to do that.
>
> Ok, do you have some resources or other information at which I should
> look? I just do not know where to start or what to check for that
> research.
>
> I looked into kernel sources and the only places where is code checking
> for IORESOURCE_WINDOW is ACPI related: arch/arm64/kernel/pci.c and
> drivers/pnp/resource.c. And I do not fully understand how is ACPI
> connected with PCI resources at this level. Other places which check
> (lib/vsprintf.c and drivers/pnp/interface.c) just use it for
> printf-formats.
Yeah, that's the kind of thing I have in mind. I can't remember if I
had any specific concern.
Bjorn
next prev parent reply other threads:[~2022-11-15 22:15 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-20 15:54 [PATCH pciutils 1/4] lspci: Show 16/32/64 bit width for address ranges behind bridge Pali Rohár
2021-12-20 15:54 ` [PATCH pciutils 2/4] lspci: Simplify printing range in show_range() Pali Rohár
2021-12-20 15:54 ` [PATCH pciutils 3/4] libpci: Add support for filling bridge resources Pali Rohár
2021-12-26 22:13 ` Martin Mareš
2021-12-26 22:20 ` Pali Rohár
2021-12-31 22:27 ` Pali Rohár
2022-01-20 20:33 ` Bjorn Helgaas
2022-01-20 20:45 ` Pali Rohár
2022-01-20 21:02 ` Bjorn Helgaas
2022-01-20 21:19 ` Pali Rohár
2022-11-11 20:09 ` IORESOURCE_WINDOW for PCI-to-PCI bridges Pali Rohár
2022-11-11 21:05 ` Bjorn Helgaas
2022-11-11 21:48 ` Pali Rohár
2022-11-15 22:15 ` Bjorn Helgaas [this message]
2021-12-20 15:54 ` [PATCH pciutils 4/4] lspci: Use PCI_FILL_BRIDGE_BASES to detect if range behind bridge is disabled or unsupported Pali Rohár
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