On Wed, Dec 02, 2020 at 05:21:58AM +0000, Surendrakumar Upadhyay, TejaskumarX wrote: > Yes it fails all the tests which are allocating from this stolen > memory bunch. For example IGT tests like " > igt@kms_frontbuffer_tracking@-[fbc|fbcpsr].* | > igt@kms_fbcon_fbt@fbc.* " are failing as they totally depend to work > on stolen memory. I'm sure that means something to graphics developers, but I have no idea! Do you have URLs for the test case source, outputs, dmesg log, lspci info, bug reports, etc? > > -----Original Message----- > > From: Bjorn Helgaas <helgaas@xxxxxxxxxx> > > Sent: 30 November 2020 22:21 > > To: Surendrakumar Upadhyay, TejaskumarX > > <tejaskumarx.surendrakumar.upadhyay@xxxxxxxxx> > > Cc: Jesse Barnes <jsbarnes@xxxxxxxxxx>; Daniel Vetter <daniel@xxxxxxxx>; > > Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>; Linux PCI <linux- > > pci@xxxxxxxxxxxxxxx>; Linux Kernel Mailing List <linux- > > kernel@xxxxxxxxxxxxxxx>; X86 ML <x86@xxxxxxxxxx>; Borislav Petkov > > <bp@xxxxxxxxx>; De Marchi, Lucas <lucas.demarchi@xxxxxxxxx>; Roper, > > Matthew D <matthew.d.roper@xxxxxxxxx>; Pandey, Hariom > > <hariom.pandey@xxxxxxxxx>; Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>; Vivi, > > Rodrigo <rodrigo.vivi@xxxxxxxxx>; David Airlie <airlied@xxxxxxxx> > > Subject: Re: [PATCH] x86/gpu: add JSL stolen memory support > > > > On Mon, Nov 30, 2020 at 10:44:14AM +0000, Surendrakumar Upadhyay, > > TejaskumarX wrote: > > > Hi All, > > > > > > Are we merging this patch in? > > > > Does it fix something? If something is broken without this patch, can we > > collect information about exactly what is broken and how it fails? > > > > But I don't object if somebody else wants to apply this. > > > > > > -----Original Message----- > > > > From: Jesse Barnes <jsbarnes@xxxxxxxxxx> > > > > Sent: 20 November 2020 03:32 > > > > To: Bjorn Helgaas <helgaas@xxxxxxxxxx> > > > > Cc: Daniel Vetter <daniel@xxxxxxxx>; Joonas Lahtinen > > > > <joonas.lahtinen@xxxxxxxxxxxxxxx>; Surendrakumar Upadhyay, > > > > TejaskumarX <tejaskumarx.surendrakumar.upadhyay@xxxxxxxxx>; Linux > > > > PCI <linux- pci@xxxxxxxxxxxxxxx>; Linux Kernel Mailing List <linux- > > > > kernel@xxxxxxxxxxxxxxx>; X86 ML <x86@xxxxxxxxxx>; Borislav Petkov > > > > <bp@xxxxxxxxx>; De Marchi, Lucas <lucas.demarchi@xxxxxxxxx>; Roper, > > > > Matthew D <matthew.d.roper@xxxxxxxxx>; Pandey, Hariom > > > > <hariom.pandey@xxxxxxxxx>; Jani Nikula > > > > <jani.nikula@xxxxxxxxxxxxxxx>; Vivi, Rodrigo > > > > <rodrigo.vivi@xxxxxxxxx>; David Airlie <airlied@xxxxxxxx> > > > > Subject: Re: [PATCH] x86/gpu: add JSL stolen memory support > > > > > > > > On Thu, Nov 19, 2020 at 11:19 AM Bjorn Helgaas <helgaas@xxxxxxxxxx> > > > > wrote: > > > > > > > > > > [+cc Jesse] > > > > > > > > > > On Thu, Nov 19, 2020 at 10:37:10AM +0100, Daniel Vetter wrote: > > > > > > On Thu, Nov 19, 2020 at 12:14 AM Bjorn Helgaas > > > > > > <helgaas@xxxxxxxxxx> > > > > wrote: > > > > > > > On Wed, Nov 18, 2020 at 10:57:26PM +0100, Daniel Vetter wrote: > > > > > > > > On Wed, Nov 18, 2020 at 5:02 PM Bjorn Helgaas > > > > <helgaas@xxxxxxxxxx> wrote: > > > > > > > > > On Fri, Nov 06, 2020 at 10:39:16AM +0100, Daniel Vetter wrote: > > > > > > > > > > On Thu, Nov 5, 2020 at 3:17 PM Bjorn Helgaas > > > > <helgaas@xxxxxxxxxx> wrote: > > > > > > > > > > > On Thu, Nov 05, 2020 at 11:46:06AM +0200, Joonas > > > > > > > > > > > Lahtinen > > > > wrote: > > > > > > > > > > > > Quoting Bjorn Helgaas (2020-11-04 19:35:56) > > > > > > > > > > > > > [+cc Jani, Joonas, Rodrigo, David, Daniel] > > > > > > > > > > > > > > > > > > > > > > > > > > On Wed, Nov 04, 2020 at 05:35:06PM +0530, Tejas > > > > > > > > > > > > > Upadhyay > > > > wrote: > > > > > > > > > > > > > > JSL re-uses the same stolen memory as ICL and EHL. > > > > > > > > > > > > > > > > > > > > > > > > > > > > Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx> > > > > > > > > > > > > > > Cc: Matt Roper <matthew.d.roper@xxxxxxxxx> > > > > > > > > > > > > > > Signed-off-by: Tejas Upadhyay > > > > > > > > > > > > > > <tejaskumarx.surendrakumar.upadhyay@xxxxxxxxx> > > > > > > > > > > > > > > > > > > > > > > > > > > I don't plan to do anything with this since > > > > > > > > > > > > > previous similar patches have gone through some > > > > > > > > > > > > > other tree, so this is > > > > just kibitzing. > > > > > > > > > > > > > > > > > > > > > > > > > > But the fact that we have this long list of Intel > > > > > > > > > > > > > devices [1] that constantly needs updates [2] is a > > > > > > > > > > > > > hint that > > > > something is wrong. > > > > > > > > > > > > > > > > > > > > > > > > We add an entry for every new integrated graphics > > > > > > > > > > > > platform. Once the platform is added, there have not > > > > > > > > > > > > been > > > > changes lately. > > > > > > > > > > > > > > > > > > > > > > > > > IIUC the general idea is that we need to discover > > > > > > > > > > > > > Intel gfx memory by looking at device-dependent > > > > > > > > > > > > > config > > > > space and add it to the E820 map. > > > > > > > > > > > > > Apparently the quirks discover this via PCI config > > > > > > > > > > > > > registers like I830_ESMRAMC, I845_ESMRAMC, etc, > > > > > > > > > > > > > and tell the driver about it via the global > > > > "intel_graphics_stolen_res"? > > > > > > > > > > > > > > > > > > > > > > > > We discover what is called the graphics data stolen > > > > > > > > > > > > memory. It is regular system memory range that is > > > > > > > > > > > > not CPU accessible. It is accessible by the integrated > > graphics only. > > > > > > > > > > > > > > > > > > > > > > > > See: > > > > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torv > > > > > > > > > > > > alds > > > > > > > > > > > > /linux.git/commit/arch/x86/kernel/early-quirks.c?h=v > > > > > > > > > > > > 5.10 > > > > > > > > > > > > -rc2&id=814c5f1f52a4beb3710317022acd6ad34fc0b6b9 > > > > > > > > > > > > > > > > > > > > > > > > > That's not the way this should work. There should > > > > > > > > > > > > > some generic, non device-dependent PCI or ACPI > > > > > > > > > > > > > method to discover the memory used, or at least > > > > > > > > > > > > > some way to do it in > > > > the driver instead of early arch code. > > > > > > > > > > > > > > > > > > > > > > > > It's used by the early BIOS/UEFI code to set up > > > > > > > > > > > > initial > > > > framebuffer. > > > > > > > > > > > > Even if i915 driver is never loaded, the memory > > > > > > > > > > > > ranges still need to be fixed. They source of the > > > > > > > > > > > > problem is that the OEM BIOS which are not under our > > > > > > > > > > > > control get the > > > > programming wrong. > > > > > > > > > > > > > > > > > > > > > > > > We used to detect the memory region size again at > > > > > > > > > > > > i915 initialization but wanted to eliminate the code > > > > > > > > > > > > duplication and resulting subtle bugs that caused. > > > > > > > > > > > > Conclusion back then was that storing the struct > > > > > > > > > > > > resource in > > > > memory is the best trade-off. > > > > > > > > > > > > > > > > > > > > > > > > > How is this *supposed* to work? Is there > > > > > > > > > > > > > something we can do in E820 or other resource > > > > > > > > > > > > > management that would > > > > make this easier? > > > > > > > > > > > > > > > > > > > > > > > > The code was added around Haswell (HSW) device > > > > > > > > > > > > generation to mitigate bugs in BIOS. It is > > > > > > > > > > > > traditionally hard to get all OEMs to fix their BIOS > > > > > > > > > > > > when things work for Windows. It's only later years > > > > > > > > > > > > when some laptop models > > > > are intended to be sold with Linux. > > > > > > > > > > > > > > > > > > > > > > > > The alternative would be to get all the OEM to fix > > > > > > > > > > > > their BIOS for Linux, but that is not very realistic > > > > > > > > > > > > given past experiences. So it seems a better choice > > > > > > > > > > > > to to add new line per platform generation to make > > > > > > > > > > > > sure the users can > > > > boot to Linux. > > > > > > > > > > > > > > > > > > > > > > How does Windows do this? Do they have to add similar > > > > > > > > > > > code for each new platform? > > > > > > > > > > > > > > > > > > > > Windows is chicken and doesn't move any mmio bar around > > > > > > > > > > on its > > > > own. > > > > > > > > > > Except if the bios explicitly told it somehow (e.g. for > > > > > > > > > > the 64bit bar stuff amd recently announced for windows, > > > > > > > > > > that linux supports since years by moving the bar). So > > > > > > > > > > except if you want to preemptively disable the pci code > > > > > > > > > > that does this anytime there's an intel gpu, this is what we > > have to do. > > > > > > > > > > > > > > > > > > I think Windows *does* move BARs (they use the more > > > > > > > > > generic terminology of "rebalancing PNP resources") in > > > > > > > > > some cases [3,4]. Of course, I'm pretty sure Windows will > > > > > > > > > only assign PCI resources inside the windows advertised in > > > > > > > > > the host bridge > > > > _CRS. > > > > > > > > > > > > > > > > > > Linux *used* to ignore that host bridge _CRS and could set > > > > > > > > > BARs to addresses that appeared available but were in fact > > > > > > > > > used by the platform somehow. But Linux has been paying > > > > > > > > > attention to host bridge _CRS for a long time now, so it > > > > > > > > > should also only assign resources inside those windows. > > > > > > > > > > > > > > > > If this behaviour is newer than the addition of these quirks > > > > > > > > then yeah they're probably not needed anymore, and we can > > > > > > > > move all this back into the driver. Do you have the commit > > > > > > > > when pci core started observing _CRS on the host bridge? > > > > > > > > > > > > > > I think the most relevant commit is this: > > > > > > > > > > > > > > 2010-02-23 7bc5e3f2be32 ("x86/PCI: use host bridge _CRS info > > > > > > > by default on 2008 and newer machines") > > > > > > > > > > > > > > but the earliest quirk I found is over three years later: > > > > > > > > > > > > > > 2013-07-26 814c5f1f52a4 ("x86: add early quirk for reserving > > > > > > > Intel graphics stolen memory v5") > > > > > > > > > > > > > > So there must be something else going on. 814c5f1f52a4 > > > > > > > mentions a couple bug reports. The dmesg from 66726 [5] shows > > > > > > > that we *are* observing the host bridge _CRS, but Linux just > > > > > > > used the BIOS configuration without changing anything: > > > > > > > > > > > > > > BIOS-e820: [mem 0x000000007f49_f000-0x000000007f5f_ffff] > > usable > > > > > > > BIOS-e820: [mem 0x00000000fec0_0000-0x00000000fec0_0fff] > > > > reserved > > > > > > > PCI: Using host bridge windows from ACPI; if necessary, use > > > > "pci=nocrs" and report a bug > > > > > > > ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff]) > > > > > > > pci_bus 0000:00: root bus resource [mem 0x7f70_0000-0xffff_ffff] > > > > > > > pci 0000:00:1c.0: PCI bridge to [bus 01] > > > > > > > pci 0000:00:1c.0: bridge window [io 0x1000-0x1fff] > > > > > > > pci 0000:00:1c.0: bridge window [mem 0xfe90_0000-0xfe9f_ffff] > > > > > > > pci 0000:00:1c.0: bridge window [mem 0x7f70_0000-0x7f8f_ffff > > 64bit > > > > pref] > > > > > > > pci 0000:01:00.0: [1814:3090] type 00 class 0x028000 > > > > > > > pci 0000:01:00.0: reg 10: [mem 0xfe90_0000-0xfe90_ffff] > > > > > > > [drm:i915_stolen_to_physical] *ERROR* conflict detected with > > > > > > > stolen region: [0x7f80_0000 - 0x8000_0000] > > > > > > > > > > > > > > So the BIOS programmed the 00:1c.0 bridge prefetchable window > > > > > > > to [mem 0x7f70_0000-0x7f8f_ffff], and i915 thinks that's a conflict. > > > > > > > > > > > > > > On this system, there are no PCI BARs in that range. 01:00.0 > > > > > > > looks like a Ralink RT3090 Wireless 802.11n device that only > > > > > > > has a non-prefetchable BAR at [mem 0xfe90_0000-0xfe90_ffff]. > > > > > > > > > > > > > > I don't know the details of the conflict. IIUC, Joonas said > > > > > > > the stolen memory is accessible only by the integrated > > > > > > > graphics, not by the CPU. The bridge window is CPU > > > > > > > accessible, of course, and the [mem 0x7f70_0000-0x7f8f_ffff] > > > > > > > range contains the addresses the CPU uses for programmed I/O to > > BARs below the bridge. > > > > > > > > > > > > > > The graphics accesses sound like they would be DMA in the > > > > > > > *bus* address space, which is frequently, but not always, > > > > > > > identical to the CPU address space. > > > > > > > > > > > > So apparently on some platforms the conflict is harmless because > > > > > > the BIOS puts BARs and stuff over it from boot-up, and things work: > > > > > > 0b6d24c01932 ("drm/i915: Don't complain about stolen conflicts > > > > > > on > > > > > > gen3") But we also had conflict reports on other machines. > > > > > > > > > > The bug reports mentioned in 814c5f1f52a4 ("x86: add early quirk > > > > > for reserving Intel graphics stolen memory v5") and 0b6d24c01932 > > > > > ("drm/i915: Don't complain about stolen conflicts on gen3") seem > > > > > to be basically complaints about the *message*, not anything > > > > > that's actually broken. > > > > > > > > > > Jesse's comment [6]: > > > > > > > > > > Given the decode priority on our GMCHs, it's fine if the regions > > > > > overlap. However it doesn't look like there's a nice way to detect > > > > > it. In this case, part of the range occupied by the stolen space is > > > > > simply "reserved" per the E820, but the rest of it is under the bus > > > > > 0 range (which kind of makes sense too). > > > > > > > > > > sounds relevant but I don't know enough to interpret it. I added > > > > > Jesse in case he wants to comment. > > > > > > > > > > > GPU does all its access with CPU address space (after the iommu, > > > > > > which is entirely integrated). So I'm not sure whether we've > > > > > > seen something go boom or whether reserving that resource was > > > > > > just precaution in > > > > > > eaba1b8f3379 ("drm/i915: Verify that our stolen memory doesn't > > > > > > conflict"), it's all a bit way back in history. > > > > > > > > > > > > So really not sure what to do here or what the risks are. > > > > > > > > > > I'm not either. Seems like we're not really converging on > > > > > anything useful we can do at this point. The only thing I can > > > > > think of would be to collect data about actual failures (not just warning > > messages). > > > > > That might lead to something we could improve in the future. > > > > > > > > I don't have any brilliant ideas here unfortunately. Maybe it's > > > > worth talking to some of the Windows folks internally to see how > > > > these ranges are handled these days and matching it? Historically > > > > this has been an area fraught with danger because getting things > > > > wrong can lead to corruption of various kinds or boot hangs. > > > > > > > > Jesse
