On Fri, May 25, 2018 at 11:30 AM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> On Fri, May 25, 2018 at 09:57:59AM -0700, Rajat Jain wrote:
>> On Thu, May 24, 2018 at 3:37 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
>> > On Tue, May 15, 2018 at 06:33:33PM -0700, Rajat Jain wrote:
>> >> If the OS and device are reporting different BAR(s), currently
>> >> the lspci will happily show the OS version with no indication what
>> >> so ever that there is a problem. This is not correct in my opinion
>> >> because lspci is often used to debug devices, so should either show
>> >> the BAR reported by the device, or atleast an indication of
>> >> out-of-sync.
>> >>
>> >> I spent a lot of time debugging a PCI device that would unexpectedly
>> >> clear out the BAR register due to some bug, and it was quite later
>> >> I realized that the lspci is showing me the OS version. So fix that.
>> >
>> > I assume (hope) that "lspci -b" would show you the hardware values.
>> > Of course, who would think to use that when you're debugging a
>> > problem. So that's not really a solution to the problem you faced.
>> >
>> >> On a system that is in problem state:
>> >>
>> >> localhost ~ # setpci -s 1:0.0 0x10.l
>> >> 00000004 <=== BAR is zeroed out
>> >> localhost ~ #
>> >>
>> >> Before:
>> >>
>> >> localhost ~ # lspci -v -s 1:0.0
>> >> 01:00.0 Network controller: Intel Corporation Wireless 7265 (rev 59)
>> >> Subsystem: Intel Corporation Dual Band Wireless-AC 7265
>> >> Flags: bus master, fast devsel, latency 0, IRQ 275
>> >> Memory at d1400000 (64-bit, non-prefetchable) [size=8K]
>> >> Capabilities: [c8] Power Management version 3
>> >> Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
>> >> Capabilities: [40] Express Endpoint, MSI 00
>> >> Capabilities: [100] Advanced Error Reporting
>> >> Capabilities: [140] Device Serial Number b4-d5-bd-ff-ff-c8-a1-6d
>> >> Capabilities: [14c] Latency Tolerance Reporting
>> >> Capabilities: [154] L1 PM Substates
>> >> Kernel driver in use: iwlwifi
>> >> Kernel modules: iwlwifi
>> >>
>> >> After:
>> >>
>> >> localhost ~ # lspci -v -s 1:0.0
>> >> 01:00.0 Network controller: Device 8086:095a (rev 59)
>> >> Subsystem: Device 8086:5010
>> >> Flags: bus master, fast devsel, latency 0, IRQ 275
>> >> [out-of-sync] Memory at d1400000 (64-bit, non-prefetchable) [size=8K]
>> >> Capabilities: [c8] Power Management version 3
>> >> Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
>> >> Capabilities: [40] Express Endpoint, MSI 00
>> >> Capabilities: [100] Advanced Error Reporting
>> >> Capabilities: [140] Device Serial Number b4-d5-bd-ff-ff-c8-a1-6d
>> >> Capabilities: [14c] Latency Tolerance Reporting
>> >> Capabilities: [154] L1 PM Substates
>> >> Kernel driver in use: iwlwifi
>> >> Kernel modules: iwlwifi
>> >
>> > I've never been quite clear on the path from hardware BAR value to
>> > lspci output. On my system,
>> >
>> > $ strace -e trace=open lspci -vs00:14.0 2>&1 | grep 00:14.0
>> >
>> > suggests that lspci reads these:
>> >
>> > /sys/bus/pci/.../resource and
>> > /sys/bus/pci/.../config
>> >
>> > "resource" uses resource_show(), where we use the result of
>> > pci_resource_to_user() on the resources in the struct pci_dev, so
>> > these are basically cached and may be out of date with respect to the
>> > hardware.
>> >
>> > "config" uses pci_read_config(), where we ultimately call the config
>> > accessors, which should give us the actual values from the hardware
>> > BARs.
>> >
>> >> Signed-off-by: Rajat Jain <rajatja@xxxxxxxxxx>
>> >> ---
>> >> lspci.c | 18 ++++++++++++++++++
>> >> 1 file changed, 18 insertions(+)
>> >>
>> >> diff --git a/lspci.c b/lspci.c
>> >> index 748452c..81c65f3 100644
>> >> --- a/lspci.c
>> >> +++ b/lspci.c
>> >> @@ -371,6 +371,20 @@ show_range(char *prefix, u64 base, u64 limit, int is_64bit)
>> >> putchar('\n');
>> >> }
>> >>
>> >> +static pciaddr_t
>> >> +bar_value(struct device *d, int i, u32 flg)
>> >> +{
>> >> + pciaddr_t val = 0;
>> >> +
>> >> + /* Read higher order 32 bits if it's a 64 bit bar in memory space */
>> >> + if (i < 5 && !(flg & PCI_BASE_ADDRESS_SPACE_IO) &&
>> >> + (flg & PCI_BASE_ADDRESS_MEM_TYPE_MASK == PCI_BASE_ADDRESS_MEM_TYPE_64))
>> >> + val = get_conf_long(d, PCI_BASE_ADDRESS_0 + 4 * (i + 1));
>> >> +
>> >> + val = (val << 32) | flg;
>> >> + return val;
>> >> +}
>> >> +
>> >> static void
>> >> show_bases(struct device *d, int cnt)
>> >> {
>> >> @@ -401,6 +415,10 @@ show_bases(struct device *d, int cnt)
>> >> flg = pos;
>> >> virtual = 1;
>> >> }
>> >> + else if (pos != bar_value(d, i, flg))
>> >> + {
>> >> + printf("[out-of-sync] ");
>> >
>> > If the host bridge does any address translation, e.g., if it uses ACPI
>> > _TRA, isn't this going to print "out-of-sync" for *every* BAR, even if
>> > it isn't really out of sync?
>>
>> Need a clarification here to ensure I understand you right. When you
>> refer to address translation above, I assume you are referring to a
>> situation where the CPU issues reads to an address X (in CPU address
>> space), which goes through a translation at the pcie root port /
>> controller, and appears as a read from address Y (as seen on the PCIe
>> bus side)?
>
> It appears as a read *to* address Y on PCI (I'm sure that's what you had
> in mind). Linux shows it like this when it enumerates the host bridge:
>
> pci_bus 0000:00: root bus resource [mem 0xf0000000000-0xf007edfffff] (bus address [0x80000000-0xfedfffff])
>
> A CPU read to physical address 0xf0000000000 will appear on PCI with the
> bus address 0x80000000. The PCI BAR would contain 0x80000000.
>
>> In such a situation, my understanding (may be wrong) was that the
>> lspci is supposed to be showing the PCI address Y for the bar (not
>> address X in physical address space). If this understanding is wrong
>> (and the lspci is supposed to show address CPU X for the bar), then
>> yes, this patch is likely not correct.
>
> My impression, based on the man page text about the "-b" option was the
> opposite:
>
> -b Bus-centric view. Show all IRQ numbers and addresses as
> seen by the cards on the PCI bus instead of as seen by the
> kernel.
Oh, sorry I was wrong. Thanks for correcting me.
>
> That suggests to me that by default lspci shows addresses as seen by
> the kernel, i.e., using CPU physical addresses. These match what
> /proc/iomem shows (at least if you look at /proc/iomem as root).
>
>> But I do think lspci should have a way to indicate when the bars in
>> /sys/bus/pci/.../resource and
>> /sys/bus/pci/.../config
>> get out of sync.
>
> I don't disagree; that does sound like it could be useful. I just
> don't know the best way to accomplish it.
Lets leave it for some other time I think. For now, the lspci -b seems
to accomplish what I want (so I'll change my scripts to use it as
needed). Thanks!
> Seems like you'd have to do
> something in resource_show() to re-read the BAR and validate the
> cache. I don't know what you do if you find that it's invalid.
>
>> >
>> >> + }
>> >> if (flg & PCI_BASE_ADDRESS_SPACE_IO)
>> >> {
>> >> pciaddr_t a = pos & PCI_BASE_ADDRESS_IO_MASK;
>> >> --
>> >> 2.17.0.441.gb46fe60e1d-goog
>> >>
