On 2019-06-27 1:50 a.m., Nicholas Johnson wrote: > On Wed, Jun 19, 2019 at 10:21:21AM -0600, Logan Gunthorpe wrote: >> *(cc'd back Bjorn and the list) >> >> On 2019-06-19 8:00 a.m., Nicholas Johnson wrote: >>> Hi Ben and Logan, >>> >>> It looks like my git send-email has been not working correctly since I >>> started trying to get these patches accepted. I may have remedied this >>> now, but I have seen that Logan tried to find these patches and failed. >>> So as a courtesy until I post PATCH v7 (hopefully correctly, this time), >>> I am forwarding you the patches. I hope you like them. I would love to >>> know of any concerns or questions you may have, and / or what happens if >>> you test them. Thanks and all the best! >>> >>> ----- Forwarded message from Nicholas Johnson <nicholas.johnson-opensource@xxxxxxxxxxxxxx> ----- >>> >>> Date: Thu, 23 May 2019 06:29:27 +0800 >>> From: Nicholas Johnson <nicholas.johnson-opensource@xxxxxxxxxxxxxx> >>> To: linux-kernel@xxxxxxxxxxxxxxx >>> Cc: linux-pci@xxxxxxxxxxxxxxx, bhelgaas@xxxxxxxxxx, mika.westerberg@xxxxxxxxxxxxxxx, corbet@xxxxxxx, Nicholas Johnson <nicholas.johnson-opensource@xxxxxxxxxxxxxx> >>> Subject: [PATCH v6 3/4] PCI: Fix bug resulting in double hpmemsize being assigned to MMIO window >>> X-Mailer: git-send-email 2.19.1 >>> >>> Background >>> ========================================================================== >>> >>> Solve bug report: >>> https://bugzilla.kernel.org/show_bug.cgi?id=203243 >> >> This is all kinds of confusing... the bug report just seems to be a copy >> of the patch set. The description of the actual symptoms of the problem >> appears to be missing from all of it. >> >>> Currently, the kernel can sometimes assign the MMIO_PREF window >>> additional size into the MMIO window, resulting in double the MMIO >>> additional size, even if the MMIO_PREF window was successful. >>> >>> This happens if in the first pass, the MMIO_PREF succeeds but the MMIO >>> fails. In the next pass, because MMIO_PREF is already assigned, the >>> attempt to assign MMIO_PREF returns an error code instead of success >>> (nothing more to do, already allocated). >>> >>> Example of problem (more context can be found in the bug report URL): >>> >>> Mainline kernel: >>> pci 0000:06:01.0: BAR 14: assigned [mem 0x90100000-0xa00fffff] = 256M >>> pci 0000:06:04.0: BAR 14: assigned [mem 0xa0200000-0xb01fffff] = 256M >>> >>> Patched kernel: >>> pci 0000:06:01.0: BAR 14: assigned [mem 0x90100000-0x980fffff] = 128M >>> pci 0000:06:04.0: BAR 14: assigned [mem 0x98200000-0xa01fffff] = 128M >>> >>> This was using pci=realloc,hpmemsize=128M,nocrs - on the same machine >>> with the same configuration, with a Ubuntu mainline kernel and a kernel >>> patched with this patch series. >>> >>> This patch is vital for the next patch in the series. The next patch >>> allows the user to specify MMIO and MMIO_PREF independently. If the >>> MMIO_PREF is set to be very large, this bug will end up more than >>> doubling the MMIO size. The bug results in the MMIO_PREF being added to >>> the MMIO window, which means doubling if MMIO_PREF size == MMIO size. >>> With a large MMIO_PREF, without this patch, the MMIO window will likely >>> fail to be assigned altogether due to lack of 32-bit address space. >>> >>> Patch notes >>> ========================================================================== >>> >>> Change find_free_bus_resource() to not skip assigned resources with >>> non-null parent. >>> >>> Add checks in pbus_size_io() and pbus_size_mem() to return success if >>> resource returned from find_free_bus_resource() is already allocated. >>> >>> This avoids pbus_size_io() and pbus_size_mem() returning error code to >>> __pci_bus_size_bridges() when a resource has been successfully assigned >>> in a previous pass. This fixes the existing behaviour where space for a >>> resource could be reserved multiple times in different parent bridge >>> windows. This also greatly reduces the number of failed BAR messages in >>> dmesg when Linux assigns resources. >> >> This patch looks like the same bug that I tracked down earlier but I >> solved in a slightly different way. See this patch[1] which is still >> under review. Can you maybe test it and see if it solves the same problem? >> >> Thanks, >> >> Logan >> >> [1] >> https://lore.kernel.org/lkml/20190531171216.20532-2-logang@xxxxxxxxxxxx/T/#u > [1] says Reported-by: Kit Chow, but I cannot find the bug report on > bugzilla.kernel.org - should I be linking the bug reports into my > version of this patch in case it is accepted? Reported-by doesn't indicate a bug report is on bugzilla. In fact I don't think too many people rely on bugzilla. It's more of a place that triage is done to send reporters to appropriate mailing lists. > Bjorn never replied to my queries about which should be accepted and > what I should do either way. For now I am moving my version of this > patch to the end of my series so that it can easily be knocked off if > Bjorn prefers your patch. I'm sure he'll get to it eventually. Probably just seeing where some of the discussion is leading. Logan
