From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: MIME-Version: 1.0 In-Reply-To: <20180524223751.GC15320@bhelgaas-glaptop.roam.corp.google.com> References: <20180516013333.135259-1-rajatja@google.com> <20180524223751.GC15320@bhelgaas-glaptop.roam.corp.google.com> From: Rajat Jain Date: Fri, 25 May 2018 09:57:59 -0700 Message-ID: Subject: Re: [PATCH] lspci: Indicate if the OS / kernel go out-of-sync on BAR To: Bjorn Helgaas Cc: Martin Mares , Bjorn Helgaas , linux-pci Content-Type: text/plain; charset="UTF-8" List-ID: On Thu, May 24, 2018 at 3:37 PM, Bjorn Helgaas 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 >> --- >> 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)? 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. 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. Thanks, Rajat > >> + } >> if (flg & PCI_BASE_ADDRESS_SPACE_IO) >> { >> pciaddr_t a = pos & PCI_BASE_ADDRESS_IO_MASK; >> -- >> 2.17.0.441.gb46fe60e1d-goog >>