From: Tomasz Nowicki <tn@semihalf.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: arnd@arndb.de, will.deacon@arm.com, catalin.marinas@arm.com,
rafael@kernel.org, hanjun.guo@linaro.org,
Lorenzo.Pieralisi@arm.com, okaya@codeaurora.org,
jchandra@broadcom.com, robert.richter@caviumnetworks.com,
mw@semihalf.com, Liviu.Dudau@arm.com, ddaney@caviumnetworks.com,
wangyijing@huawei.com, Suravee.Suthikulpanit@amd.com,
msalter@redhat.com, linux-pci@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org,
linux-kernel@vger.kernel.org, linaro-acpi@lists.linaro.org,
jcm@redhat.com, andrea.gallo@linaro.org, dhdang@apm.com,
jeremy.linton@arm.com, liudongdong3@huawei.com,
cov@codeaurora.org
Subject: Re: [PATCH V8 7/9] acpi: Add generic MCFG table handling
Date: Wed, 8 Jun 2016 15:44:19 +0200 [thread overview]
Message-ID: <57582133.8060402@semihalf.com> (raw)
In-Reply-To: <20160608131709.GB16764@localhost>
On 08.06.2016 15:17, Bjorn Helgaas wrote:
> On Wed, Jun 08, 2016 at 02:21:30PM +0200, Tomasz Nowicki wrote:
>> On 08.06.2016 03:56, Bjorn Helgaas wrote:
>>> On Mon, May 30, 2016 at 05:14:20PM +0200, Tomasz Nowicki wrote:
>>>> In order to handle PCI config space regions properly in ACPI, new MCFG
>>>> interface is defined which does sanity checks on MCFG table and keeps its
>>>> root pointer. The user is able to lookup MCFG regions based on
>>>> host bridge root structure and domain:bus_start:bus_end touple.
>>>> Use pci_mmcfg_late_init old prototype to avoid another function name.
>
>>>> + /* found matching entry, bus range check */
>>>> + if (entry->end_bus_number != bus_res->end) {
>>>> + resource_size_t bus_end = min_t(resource_size_t,
>>>> + entry->end_bus_number, bus_res->end);
>>>> + pr_warn("%04x:%pR bus end mismatch, using %02lx\n",
>>>> + root->segment, bus_res, (unsigned long)bus_end);
>>>> + bus_res->end = bus_end;
>>>> + }
>>
>> What about bus end mismatch case? Should we trim the host bridge bus
>> range or expect MCFG entry covers that range? Sometimes we get
>> _BBN-0xFF bus range, not from _CRS.
>
> Lack of a bus range in _CRS is a firmware defect. There's a comment
> about this in acpi_pci_root_add(). On x86, we probably had to live
> with firmware in the field that had this defect. I think we should
> expect all ARM64 systems to provide a bus number range in _CRS, and
> fail the attach if it's not there.
>
> I don't think we should warn about an MCFG entry that covers more than
> the _CRS bus range. On x86, it's common to have something like:
>
> ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-7f])
> ACPI: PCI Root Bridge [PCI1] (domain 0000 [bus 80-ff])
>
> with a single MCFG entry that covers [bus 00-ff]. That seems
> reasonable and I don't think it's worth warning about it.
>
> If the MCFG entry doesn't cover all of a _CRS bus range, we should
> just fail so we can find and fix broken firmware.
Make sense to me.
>
>>>> +/* Interface called by ACPI - parse and save MCFG table */
>>>
>>> I think we save a *pointer* to the MCFG table, not the table itself.
>>
>> Right, the comment is broken.
>>
>>> And acpi_table_parse() calls early_acpi_os_unmap_memory() immediately
>>> after it calls pci_mcfg_parse(), so I'm doubtful that the pointer
>>> remains valid.
>>
>> At this stage early_acpi_os_unmap_memory() is doing nothing since
>> acpi_early_init() set acpi_gbl_permanent_mmap to 1 way before. The
>> pointer is fine then.
>
> Hmmm... I see your argument, but this is a problem waiting to happen.
> We should not depend on the internal implementation of
> early_acpi_os_unmap_memory(). The pattern of:
>
> y = x;
> unmap(x);
> z = *y;
>
> is just broken and we shouldn't expect readers to recognize that "oh,
> unmap() isn't really unmapping anything in this special case, so this
> looks wrong but is really fine."
>
Right, so we are back to MCFG cache.
Thanks,
Tomasz
next prev parent reply other threads:[~2016-06-08 13:44 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-30 15:14 [PATCH V8 0/9] Support for ARM64 ACPI based PCI host controller Tomasz Nowicki
2016-05-30 15:14 ` [PATCH V8 1/9] PCI: ecam: move ecam.h to linux/include/pci-ecam.h Tomasz Nowicki
2016-06-02 9:48 ` Lorenzo Pieralisi
2016-05-30 15:14 ` [PATCH V8 2/9] PCI: ecam: Add parent device field to pci_config_window Tomasz Nowicki
2016-06-02 10:13 ` Lorenzo Pieralisi
2016-05-30 15:14 ` [PATCH V8 3/9] pci: Add new function to unmap IO resources Tomasz Nowicki
2016-06-02 16:50 ` Lorenzo Pieralisi
2016-05-30 15:14 ` [PATCH V8 4/9] acpi, pci: Support IO resources when parsing PCI host bridge resources Tomasz Nowicki
2016-06-02 17:30 ` Lorenzo Pieralisi
2016-06-07 23:56 ` Bjorn Helgaas
2016-05-30 15:14 ` [PATCH V8 5/9] pci, acpi: add acpi hook to assign domain number Tomasz Nowicki
2016-06-08 0:15 ` Bjorn Helgaas
2016-06-08 10:21 ` Tomasz Nowicki
2016-06-08 13:22 ` Bjorn Helgaas
2016-06-10 15:14 ` Lorenzo Pieralisi
2016-06-10 15:49 ` Lorenzo Pieralisi
2016-06-10 16:49 ` Tomasz Nowicki
2016-06-10 18:18 ` Bjorn Helgaas
2016-06-10 18:54 ` Jon Masters
2016-05-30 15:14 ` [PATCH V8 6/9] arm64, pci, acpi: ACPI support for legacy IRQs parsing and consolidation with DT code Tomasz Nowicki
2016-05-30 15:14 ` [PATCH V8 7/9] acpi: Add generic MCFG table handling Tomasz Nowicki
2016-06-03 11:38 ` Lorenzo Pieralisi
2016-06-06 12:55 ` Tomasz Nowicki
2016-06-08 1:56 ` Bjorn Helgaas
2016-06-08 12:21 ` Tomasz Nowicki
2016-06-08 13:17 ` Bjorn Helgaas
2016-06-08 13:44 ` Tomasz Nowicki [this message]
2016-05-30 15:14 ` [PATCH V8 8/9] arm64, pci, acpi: Provide ACPI-specific prerequisites for PCI bus enumeration Tomasz Nowicki
2016-06-02 9:45 ` Lorenzo Pieralisi
2016-06-02 9:51 ` Tomasz Nowicki
2016-05-30 15:14 ` [PATCH V8 9/9] pci, acpi: ARM64 support for ACPI based generic PCI host controller Tomasz Nowicki
2016-05-30 15:38 ` Arnd Bergmann
2016-05-30 16:13 ` Jayachandran C
2016-06-02 9:35 ` Lorenzo Pieralisi
2016-06-02 9:44 ` Tomasz Nowicki
2016-06-08 2:14 ` Bjorn Helgaas
2016-06-01 7:36 ` [PATCH V8 0/9] Support for ARM64 ACPI based " Gabriele Paoloni
2016-06-02 7:31 ` Jon Masters
2016-06-02 10:06 ` Gabriele Paoloni
2016-06-02 8:52 ` Tomasz Nowicki
2016-06-02 9:58 ` Gabriele Paoloni
2016-06-02 8:48 ` Jon Masters
2016-06-07 23:13 ` Bjorn Helgaas
2016-06-08 9:20 ` Dongdong Liu
2016-06-09 16:45 ` Suravee Suthikulanit
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