| Message ID | CAKv+Gu-J664KXaZR19nViq4o1n_x=P-trsZ0oNDiONuBpAcd7A@mail.gmail.com |
|---|---|
| State | Not Applicable |
| Headers | show |
On Thu, Mar 23, 2017 at 12:25:48PM +0000, Ard Biesheuvel wrote: > On 23 March 2017 at 10:57, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: > > On Thu, Mar 23, 2017 at 09:04:03AM +0000, Ard Biesheuvel wrote: > >> On 23 March 2017 at 08:48, Lukas Wunner <lukas@wunner.de> wrote: > >> > On Wed, Mar 22, 2017 at 07:32:43PM +0000, Ard Biesheuvel wrote: > >> >> On 22 March 2017 at 19:31, Lukas Wunner <lukas@wunner.de> wrote: > >> >> > On Wed, Mar 22, 2017 at 03:30:29PM +0000, Ard Biesheuvel wrote: > >> >> >> On UEFI systems, the PCI subsystem is enumerated by the firmware, > >> >> >> and if a graphical framebuffer is exposed by a PCI device, its base > >> >> >> address and size are exposed to the OS via the Graphics Output > >> >> >> Protocol (GOP). > >> >> >> > >> >> >> On arm64 PCI systems, the entire PCI hierarchy is reconfigured from > >> >> >> scratch at boot. This may result in the GOP framebuffer address to > >> >> >> become stale, if the BAR covering the framebuffer is modified. This > >> >> >> will cause the framebuffer to become unresponsive, and may in some > >> >> >> cases result in unpredictable behavior if the range is reassigned to > >> >> >> another device. > >> >> > > >> >> > Hm, commit message seems to indicate the issue is restricted to arm64, > >> >> > yet there's no IS_ENABLED(ARM64) to constrain the added code to that arch? > >> >> > >> >> True. I am eager to get some x86 coverage for this, since I would > >> >> expect this not to do any harm. But I'm fine with making it ARM/arm64 > >> >> specific in the final version. > >> > > >> > I see. IIUC, this is only a problem because pci_bus_assign_resources() > >> > is called from arch/arm64/kernel/pci.c:pci_acpi_scan_root() (as well as > >> > the host drivers) and x86 isn't affected because it doesn't do that. > >> > > >> > >> Correct. But on x86 (or rather, on a PC), you can be sure that UEFI > >> (or the legacy PCI bios) performed the resource assignment already. > >> One could argue that this is equally the case when running arm64 in > >> ACPI mode, but in general, you cannot assume the presence of firmware > >> on ARM/arm64 that has already taken care of this, and so the state of > >> the BARs has to be presumed invalid. > > > > The story is a bit more convoluted than that owing to x86 (and other > > arches) legacy. > > > > x86 tries to claim all PCI resources (in two passes - first enabled > > devices, second disabled devices) and that predates ACPI/UEFI. > > > > Mind, x86 reassign resources that can't be claimed too, the only > > difference with ARM64 is that, for the better or the worse, we > > have decided not to claim the FW PCI set-up on ARM64 even if it > > is sane, we do not even try, it was a deliberate choice. > > > > This patch should be harmless on x86 since if the FB PCI BAR is set > > up sanely, claiming it again should be a nop (to be checked). > > > > I have checked this with OVMF under QEMU. Claiming the resource early > like we do this in this patch does not result in any diagnostic output > or other symptoms that would suggest that anything unexpected occurs. There is something that I do not understand on how the resource claiming works on x86. IIUC on x86, resource claiming is done in: arch/x86/pci/legacy.c pci_subsys_init() -> pcibios_init() -> pcibios_resource_survey() pci_subsys_init() is run in a subsys_initcall. Now, how do we ensure that resource claiming is carried out _after_ the PCI root busses have been actually scanned ? The ACPI scan handler interface (so the interface to actually scan a PCI root bridge in ACPI) is initialized in acpi_init() (which is a subsys_initcall), how do we guarantee that is run before pci_subsys_init() ? x86 implements pcibios_resource_survey_bus(), but that's called only for hotplugged bridges (?): drivers/acpi/pci_root.c -> acpi_pci_root_add() From the log below, I see two options: - x86 pcibios_resource_survey() is called before any root bus is added (so it does precious little) - x86 pcibios_resource_survey() is called after root busses are added and the PCI device fixup has been applied (and the additional claim in it succeeds silently) I am certainly missing something here, I will grab an x86 box to add a couple of logs and see if my assumptions are correct, I would like to get to the bottom of this, I think that's important. Lorenzo > For the record: I applied the following hunk on top of the current > version of this patch > > diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c > index 88f653864a01..98b7c437a448 100644 > --- a/drivers/video/fbdev/efifb.c > +++ b/drivers/video/fbdev/efifb.c > @@ -380,7 +380,10 @@ static void claim_efifb_bar(struct pci_dev *dev, int idx) > return; > } > > - if (pci_claim_resource(dev, idx)) { > + if (dev->resource[idx].parent != NULL) { > + dev_info(&dev->dev, "BAR %d: resource already claimed\n", idx); > + while (1) { asm ("hlt"); } > + } else if (pci_claim_resource(dev, idx)) { > pci_dev_disabled = true; > dev_err(&dev->dev, > "BAR %d: failed to claim resource for efifb!\n", idx); > > and got the following output in the kernel log related to BDF 0/2/0 and efifb > > pci 0000:00:02.0: [1234:1111] type 00 class 0x030000 > pci 0000:00:02.0: reg 0x10: [mem 0x80000000-0x80ffffff pref] > pci 0000:00:02.0: reg 0x18: [mem 0x81020000-0x81020fff] > pci 0000:00:02.0: reg 0x30: [mem 0xffff0000-0xffffffff pref] > pci 0000:00:02.0: BAR 0: assigned to efifb > pci 0000:00:02.0: can't claim BAR 6 [mem 0xffff0000-0xffffffff pref]: > no compatible bridge window > pci 0000:00:02.0: BAR 6: assigned [mem 0x08040000-0x0804ffff pref] > pci 0000:00:02.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff] > efifb: probing for efifb > efifb: framebuffer at 0x80000000, using 1876k, total 1875k > efifb: mode is 800x600x32, linelength=3200, pages=1 > efifb: scrolling: redraw > efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0 > > whereas a kernel without this patch gives me > > pci 0000:00:02.0: [1234:1111] type 00 class 0x030000 > pci 0000:00:02.0: reg 0x10: [mem 0x80000000-0x80ffffff pref] > pci 0000:00:02.0: reg 0x18: [mem 0x81020000-0x81020fff] > pci 0000:00:02.0: reg 0x30: [mem 0xffff0000-0xffffffff pref] > pci 0000:00:02.0: can't claim BAR 6 [mem 0xffff0000-0xffffffff pref]: > no compatible bridge window > pci 0000:00:02.0: BAR 6: assigned [mem 0x08040000-0x0804ffff pref] > pci 0000:00:02.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff] > efifb: probing for efifb > efifb: framebuffer at 0x80000000, using 1876k, total 1875k > efifb: mode is 800x600x32, linelength=3200, pages=1 > efifb: scrolling: redraw > efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0 > > /proc/iomem looks exactly the same. > > So in summary, x86 does not seem to care. > > Furthermore, I tested with this change, as suggested by Lukas > > diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c > index 88f653864a01..c72d84590343 100644 > --- a/drivers/video/fbdev/efifb.c > +++ b/drivers/video/fbdev/efifb.c > @@ -417,4 +417,5 @@ static void efifb_fixup_resources(struct pci_dev *dev) > } > } > } > -DECLARE_PCI_FIXUP_HEADER(PCI_ANY_ID, PCI_ANY_ID, efifb_fixup_resources); > +DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY, > + 16, efifb_fixup_resources); > > > which does appear to work fine, and thinking about it, I feel there is > only so much we can do to sanity check the efifb against the PCI setup > performed by the firmware, so I am inclined to fold this in.
On 23 March 2017 at 14:31, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: > On Thu, Mar 23, 2017 at 12:25:48PM +0000, Ard Biesheuvel wrote: >> On 23 March 2017 at 10:57, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: >> > On Thu, Mar 23, 2017 at 09:04:03AM +0000, Ard Biesheuvel wrote: >> >> On 23 March 2017 at 08:48, Lukas Wunner <lukas@wunner.de> wrote: >> >> > On Wed, Mar 22, 2017 at 07:32:43PM +0000, Ard Biesheuvel wrote: >> >> >> On 22 March 2017 at 19:31, Lukas Wunner <lukas@wunner.de> wrote: >> >> >> > On Wed, Mar 22, 2017 at 03:30:29PM +0000, Ard Biesheuvel wrote: >> >> >> >> On UEFI systems, the PCI subsystem is enumerated by the firmware, >> >> >> >> and if a graphical framebuffer is exposed by a PCI device, its base >> >> >> >> address and size are exposed to the OS via the Graphics Output >> >> >> >> Protocol (GOP). >> >> >> >> >> >> >> >> On arm64 PCI systems, the entire PCI hierarchy is reconfigured from >> >> >> >> scratch at boot. This may result in the GOP framebuffer address to >> >> >> >> become stale, if the BAR covering the framebuffer is modified. This >> >> >> >> will cause the framebuffer to become unresponsive, and may in some >> >> >> >> cases result in unpredictable behavior if the range is reassigned to >> >> >> >> another device. >> >> >> > >> >> >> > Hm, commit message seems to indicate the issue is restricted to arm64, >> >> >> > yet there's no IS_ENABLED(ARM64) to constrain the added code to that arch? >> >> >> >> >> >> True. I am eager to get some x86 coverage for this, since I would >> >> >> expect this not to do any harm. But I'm fine with making it ARM/arm64 >> >> >> specific in the final version. >> >> > >> >> > I see. IIUC, this is only a problem because pci_bus_assign_resources() >> >> > is called from arch/arm64/kernel/pci.c:pci_acpi_scan_root() (as well as >> >> > the host drivers) and x86 isn't affected because it doesn't do that. >> >> > >> >> >> >> Correct. But on x86 (or rather, on a PC), you can be sure that UEFI >> >> (or the legacy PCI bios) performed the resource assignment already. >> >> One could argue that this is equally the case when running arm64 in >> >> ACPI mode, but in general, you cannot assume the presence of firmware >> >> on ARM/arm64 that has already taken care of this, and so the state of >> >> the BARs has to be presumed invalid. >> > >> > The story is a bit more convoluted than that owing to x86 (and other >> > arches) legacy. >> > >> > x86 tries to claim all PCI resources (in two passes - first enabled >> > devices, second disabled devices) and that predates ACPI/UEFI. >> > >> > Mind, x86 reassign resources that can't be claimed too, the only >> > difference with ARM64 is that, for the better or the worse, we >> > have decided not to claim the FW PCI set-up on ARM64 even if it >> > is sane, we do not even try, it was a deliberate choice. >> > >> > This patch should be harmless on x86 since if the FB PCI BAR is set >> > up sanely, claiming it again should be a nop (to be checked). >> > >> >> I have checked this with OVMF under QEMU. Claiming the resource early >> like we do this in this patch does not result in any diagnostic output >> or other symptoms that would suggest that anything unexpected occurs. > > There is something that I do not understand on how the resource > claiming works on x86. IIUC on x86, resource claiming is done in: > > arch/x86/pci/legacy.c > > pci_subsys_init() > -> pcibios_init() > -> pcibios_resource_survey() > > pci_subsys_init() is run in a subsys_initcall. > Yes, the call trace I get for the resource claim for the efifb BAR without this patch is pci_subsys_init+0x3f/0x43 - pcibios_init+0x2c/0x3d -- pcibios_resource_survey+0x38/0x6a --- pci_legacy_init+0x2e/0x2e ---- pcibios_allocate_resources+0x8a/0x240 ----- pci_claim_resource+0xdc/0x140 > Now, how do we ensure that resource claiming is carried out _after_ > the PCI root busses have been actually scanned ? > > The ACPI scan handler interface (so the interface to actually scan > a PCI root bridge in ACPI) is initialized in acpi_init() (which > is a subsys_initcall), how do we guarantee that is run before > pci_subsys_init() ? > $ nm vmlinux |grep -E '__initcall_(acpi_init|pci_subsys_init)' ffffffff81d540b8 t __initcall_acpi_init4 ffffffff81d54158 t __initcall_pci_subsys_init4 so it appears to depend on link order currently.
On 23 March 2017 at 15:15, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote: > On 23 March 2017 at 14:31, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: >> On Thu, Mar 23, 2017 at 12:25:48PM +0000, Ard Biesheuvel wrote: >>> On 23 March 2017 at 10:57, Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote: >>> > On Thu, Mar 23, 2017 at 09:04:03AM +0000, Ard Biesheuvel wrote: >>> >> On 23 March 2017 at 08:48, Lukas Wunner <lukas@wunner.de> wrote: >>> >> > On Wed, Mar 22, 2017 at 07:32:43PM +0000, Ard Biesheuvel wrote: >>> >> >> On 22 March 2017 at 19:31, Lukas Wunner <lukas@wunner.de> wrote: >>> >> >> > On Wed, Mar 22, 2017 at 03:30:29PM +0000, Ard Biesheuvel wrote: >>> >> >> >> On UEFI systems, the PCI subsystem is enumerated by the firmware, >>> >> >> >> and if a graphical framebuffer is exposed by a PCI device, its base >>> >> >> >> address and size are exposed to the OS via the Graphics Output >>> >> >> >> Protocol (GOP). >>> >> >> >> >>> >> >> >> On arm64 PCI systems, the entire PCI hierarchy is reconfigured from >>> >> >> >> scratch at boot. This may result in the GOP framebuffer address to >>> >> >> >> become stale, if the BAR covering the framebuffer is modified. This >>> >> >> >> will cause the framebuffer to become unresponsive, and may in some >>> >> >> >> cases result in unpredictable behavior if the range is reassigned to >>> >> >> >> another device. >>> >> >> > >>> >> >> > Hm, commit message seems to indicate the issue is restricted to arm64, >>> >> >> > yet there's no IS_ENABLED(ARM64) to constrain the added code to that arch? >>> >> >> >>> >> >> True. I am eager to get some x86 coverage for this, since I would >>> >> >> expect this not to do any harm. But I'm fine with making it ARM/arm64 >>> >> >> specific in the final version. >>> >> > >>> >> > I see. IIUC, this is only a problem because pci_bus_assign_resources() >>> >> > is called from arch/arm64/kernel/pci.c:pci_acpi_scan_root() (as well as >>> >> > the host drivers) and x86 isn't affected because it doesn't do that. >>> >> > >>> >> >>> >> Correct. But on x86 (or rather, on a PC), you can be sure that UEFI >>> >> (or the legacy PCI bios) performed the resource assignment already. >>> >> One could argue that this is equally the case when running arm64 in >>> >> ACPI mode, but in general, you cannot assume the presence of firmware >>> >> on ARM/arm64 that has already taken care of this, and so the state of >>> >> the BARs has to be presumed invalid. >>> > >>> > The story is a bit more convoluted than that owing to x86 (and other >>> > arches) legacy. >>> > >>> > x86 tries to claim all PCI resources (in two passes - first enabled >>> > devices, second disabled devices) and that predates ACPI/UEFI. >>> > >>> > Mind, x86 reassign resources that can't be claimed too, the only >>> > difference with ARM64 is that, for the better or the worse, we >>> > have decided not to claim the FW PCI set-up on ARM64 even if it >>> > is sane, we do not even try, it was a deliberate choice. >>> > >>> > This patch should be harmless on x86 since if the FB PCI BAR is set >>> > up sanely, claiming it again should be a nop (to be checked). >>> > >>> >>> I have checked this with OVMF under QEMU. Claiming the resource early >>> like we do this in this patch does not result in any diagnostic output >>> or other symptoms that would suggest that anything unexpected occurs. >> >> There is something that I do not understand on how the resource >> claiming works on x86. IIUC on x86, resource claiming is done in: >> >> arch/x86/pci/legacy.c >> >> pci_subsys_init() >> -> pcibios_init() >> -> pcibios_resource_survey() >> >> pci_subsys_init() is run in a subsys_initcall. >> > > Yes, the call trace I get for the resource claim for the efifb BAR > without this patch is > > pci_subsys_init+0x3f/0x43 > - pcibios_init+0x2c/0x3d > -- pcibios_resource_survey+0x38/0x6a > --- pci_legacy_init+0x2e/0x2e > ---- pcibios_allocate_resources+0x8a/0x240 > ----- pci_claim_resource+0xdc/0x140 > > >> Now, how do we ensure that resource claiming is carried out _after_ >> the PCI root busses have been actually scanned ? >> >> The ACPI scan handler interface (so the interface to actually scan >> a PCI root bridge in ACPI) is initialized in acpi_init() (which >> is a subsys_initcall), how do we guarantee that is run before >> pci_subsys_init() ? >> > > $ nm vmlinux |grep -E '__initcall_(acpi_init|pci_subsys_init)' > ffffffff81d540b8 t __initcall_acpi_init4 > ffffffff81d54158 t __initcall_pci_subsys_init4 > > so it appears to depend on link order currently. Bjorn, what is your take on this? Claiming the BAR resources associated with the efifb region from a DECLARE_PCI_FIXUP_HEADER() handler does not seem to interfere with the way resources are claimed later on. For arm64, we need this to ensure that the BAR doesn't move, but for x86 this does not seem to be an issue. This means we could potentially make the quirk ARM-only, but I am a bit reluctant to do so and create even more divergence. Thanks, Ard.
diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c index 88f653864a01..98b7c437a448 100644 --- a/drivers/video/fbdev/efifb.c +++ b/drivers/video/fbdev/efifb.c @@ -380,7 +380,10 @@ static void claim_efifb_bar(struct pci_dev *dev, int idx) return; } - if (pci_claim_resource(dev, idx)) { + if (dev->resource[idx].parent != NULL) { + dev_info(&dev->dev, "BAR %d: resource already claimed\n", idx); + while (1) { asm ("hlt"); } + } else if (pci_claim_resource(dev, idx)) { pci_dev_disabled = true; dev_err(&dev->dev, "BAR %d: failed to claim resource for efifb!\n", idx); and got the following output in the kernel log related to BDF 0/2/0 and efifb pci 0000:00:02.0: [1234:1111] type 00 class 0x030000 pci 0000:00:02.0: reg 0x10: [mem 0x80000000-0x80ffffff pref] pci 0000:00:02.0: reg 0x18: [mem 0x81020000-0x81020fff] pci 0000:00:02.0: reg 0x30: [mem 0xffff0000-0xffffffff pref] pci 0000:00:02.0: BAR 0: assigned to efifb pci 0000:00:02.0: can't claim BAR 6 [mem 0xffff0000-0xffffffff pref]: no compatible bridge window pci 0000:00:02.0: BAR 6: assigned [mem 0x08040000-0x0804ffff pref] pci 0000:00:02.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff] efifb: probing for efifb efifb: framebuffer at 0x80000000, using 1876k, total 1875k efifb: mode is 800x600x32, linelength=3200, pages=1 efifb: scrolling: redraw efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0 whereas a kernel without this patch gives me pci 0000:00:02.0: [1234:1111] type 00 class 0x030000 pci 0000:00:02.0: reg 0x10: [mem 0x80000000-0x80ffffff pref] pci 0000:00:02.0: reg 0x18: [mem 0x81020000-0x81020fff] pci 0000:00:02.0: reg 0x30: [mem 0xffff0000-0xffffffff pref] pci 0000:00:02.0: can't claim BAR 6 [mem 0xffff0000-0xffffffff pref]: no compatible bridge window pci 0000:00:02.0: BAR 6: assigned [mem 0x08040000-0x0804ffff pref] pci 0000:00:02.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff] efifb: probing for efifb efifb: framebuffer at 0x80000000, using 1876k, total 1875k efifb: mode is 800x600x32, linelength=3200, pages=1 efifb: scrolling: redraw efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0 /proc/iomem looks exactly the same. So in summary, x86 does not seem to care. Furthermore, I tested with this change, as suggested by Lukas diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c index 88f653864a01..c72d84590343 100644 --- a/drivers/video/fbdev/efifb.c +++ b/drivers/video/fbdev/efifb.c @@ -417,4 +417,5 @@ static void efifb_fixup_resources(struct pci_dev *dev) } } } -DECLARE_PCI_FIXUP_HEADER(PCI_ANY_ID, PCI_ANY_ID, efifb_fixup_resources); +DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY, + 16, efifb_fixup_resources);