| Message ID | 2762ffd4c196dc91d62e10eb8b753f256ea9b629.1568375317.git.robin.murphy@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iommu/arm-smmu: Report USF more clearly | expand |
On 13/09/2019 12:48, Robin Murphy wrote: > Although CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT is a welcome tool > for smoking out inadequate firmware, the failure mode is non-obvious > and can be confusing for end users. Add some special-case reporting of > Unidentified Stream Faults to help clarify this particular symptom. > > CC: Douglas Anderson <dianders@chromium.org> > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > drivers/iommu/arm-smmu.c | 5 +++++ > drivers/iommu/arm-smmu.h | 2 ++ > 2 files changed, 7 insertions(+) > > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > index b7cf24402a94..76ac8c180695 100644 > --- a/drivers/iommu/arm-smmu.c > +++ b/drivers/iommu/arm-smmu.c > @@ -499,6 +499,11 @@ static irqreturn_t arm_smmu_global_fault(int irq, void *dev) > dev_err_ratelimited(smmu->dev, > "\tGFSR 0x%08x, GFSYNR0 0x%08x, GFSYNR1 0x%08x, GFSYNR2 0x%08x\n", > gfsr, gfsynr0, gfsynr1, gfsynr2); > + if (IS_ENABLED(CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT) && > + (gfsr & sGFSR_USF)) > + dev_err_ratelimited(smmu->dev, > + "Stream ID %hu may not be described by firmware, try booting with \"arm-smmu.disable_bypass=0\"\n", > + (u16)gfsynr1); > > arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_sGFSR, gfsr); > return IRQ_HANDLED; > diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h > index c9c13b5785f2..46f7e161e83e 100644 > --- a/drivers/iommu/arm-smmu.h > +++ b/drivers/iommu/arm-smmu.h > @@ -79,6 +79,8 @@ > #define ID7_MINOR GENMASK(3, 0) > > #define ARM_SMMU_GR0_sGFSR 0x48 > +#define sGFSR_USF BIT(2) Sigh... and of course what I actually meant here was that this is the 2nd bit, which is bit 1, which is also 2. I blame Friday :( Robin. > + > #define ARM_SMMU_GR0_sGFSYNR0 0x50 > #define ARM_SMMU_GR0_sGFSYNR1 0x54 > #define ARM_SMMU_GR0_sGFSYNR2 0x58 >
On Fri, 2019-09-13 at 12:48 +0100, Robin Murphy wrote: > Although CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT is a welcome tool > for smoking out inadequate firmware, the failure mode is non-obvious > and can be confusing for end users. Add some special-case reporting of > Unidentified Stream Faults to help clarify this particular symptom. > > CC: Douglas Anderson <dianders@chromium.org> > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > drivers/iommu/arm-smmu.c | 5 +++++ > drivers/iommu/arm-smmu.h | 2 ++ > 2 files changed, 7 insertions(+) > > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > index b7cf24402a94..76ac8c180695 100644 > --- a/drivers/iommu/arm-smmu.c > +++ b/drivers/iommu/arm-smmu.c > @@ -499,6 +499,11 @@ static irqreturn_t arm_smmu_global_fault(int irq, void *dev) > dev_err_ratelimited(smmu->dev, > "\tGFSR 0x%08x, GFSYNR0 0x%08x, GFSYNR1 0x%08x, GFSYNR2 0x%08x\n", > gfsr, gfsynr0, gfsynr1, gfsynr2); > + if (IS_ENABLED(CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT) && > + (gfsr & sGFSR_USF)) > + dev_err_ratelimited(smmu->dev, > + "Stream ID %hu may not be described by firmware, try booting with \"arm-smmu.disable_bypass=0\"\n", > + (u16)gfsynr1); dev_err_once(), i.e., don't need to remind people to set "arm- smmu.disable_bypass=0" multiple times. > > arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_sGFSR, gfsr); > return IRQ_HANDLED; > diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h > index c9c13b5785f2..46f7e161e83e 100644 > --- a/drivers/iommu/arm-smmu.h > +++ b/drivers/iommu/arm-smmu.h > @@ -79,6 +79,8 @@ > #define ID7_MINOR GENMASK(3, 0) > > #define ARM_SMMU_GR0_sGFSR 0x48 > +#define sGFSR_USF BIT(2) > + > #define ARM_SMMU_GR0_sGFSYNR0 0x50 > #define ARM_SMMU_GR0_sGFSYNR1 0x54 > #define ARM_SMMU_GR0_sGFSYNR2 0x58
On 13/09/2019 15:35, Qian Cai wrote: > On Fri, 2019-09-13 at 12:48 +0100, Robin Murphy wrote: >> Although CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT is a welcome tool >> for smoking out inadequate firmware, the failure mode is non-obvious >> and can be confusing for end users. Add some special-case reporting of >> Unidentified Stream Faults to help clarify this particular symptom. >> >> CC: Douglas Anderson <dianders@chromium.org> >> Signed-off-by: Robin Murphy <robin.murphy@arm.com> >> --- >> drivers/iommu/arm-smmu.c | 5 +++++ >> drivers/iommu/arm-smmu.h | 2 ++ >> 2 files changed, 7 insertions(+) >> >> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c >> index b7cf24402a94..76ac8c180695 100644 >> --- a/drivers/iommu/arm-smmu.c >> +++ b/drivers/iommu/arm-smmu.c >> @@ -499,6 +499,11 @@ static irqreturn_t arm_smmu_global_fault(int irq, void *dev) >> dev_err_ratelimited(smmu->dev, >> "\tGFSR 0x%08x, GFSYNR0 0x%08x, GFSYNR1 0x%08x, GFSYNR2 0x%08x\n", >> gfsr, gfsynr0, gfsynr1, gfsynr2); >> + if (IS_ENABLED(CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT) && >> + (gfsr & sGFSR_USF)) >> + dev_err_ratelimited(smmu->dev, >> + "Stream ID %hu may not be described by firmware, try booting with \"arm-smmu.disable_bypass=0\"\n", >> + (u16)gfsynr1); > > dev_err_once(), i.e., don't need to remind people to set "arm- > smmu.disable_bypass=0" multiple times. Indeed, but in many cases it then quickly gets buried by an unending storm of repeated faults (not every console has capture and scrollback...) Given that it's a "this is why your machine is on fire" kind of message, I figured that it's probably best to err on the side of visibility. Robin. >> >> arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_sGFSR, gfsr); >> return IRQ_HANDLED; >> diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h >> index c9c13b5785f2..46f7e161e83e 100644 >> --- a/drivers/iommu/arm-smmu.h >> +++ b/drivers/iommu/arm-smmu.h >> @@ -79,6 +79,8 @@ >> #define ID7_MINOR GENMASK(3, 0) >> >> #define ARM_SMMU_GR0_sGFSR 0x48 >> +#define sGFSR_USF BIT(2) >> + >> #define ARM_SMMU_GR0_sGFSYNR0 0x50 >> #define ARM_SMMU_GR0_sGFSYNR1 0x54 >> #define ARM_SMMU_GR0_sGFSYNR2 0x58
Hi, On Fri, Sep 13, 2019 at 4:48 AM Robin Murphy <robin.murphy@arm.com> wrote: > > Although CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT is a welcome tool > for smoking out inadequate firmware, the failure mode is non-obvious > and can be confusing for end users. Add some special-case reporting of > Unidentified Stream Faults to help clarify this particular symptom. > > CC: Douglas Anderson <dianders@chromium.org> nit that I believe that "Cc" (lowercase 2nd c) is correct. > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > drivers/iommu/arm-smmu.c | 5 +++++ > drivers/iommu/arm-smmu.h | 2 ++ > 2 files changed, 7 insertions(+) > > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > index b7cf24402a94..76ac8c180695 100644 > --- a/drivers/iommu/arm-smmu.c > +++ b/drivers/iommu/arm-smmu.c > @@ -499,6 +499,11 @@ static irqreturn_t arm_smmu_global_fault(int irq, void *dev) > dev_err_ratelimited(smmu->dev, > "\tGFSR 0x%08x, GFSYNR0 0x%08x, GFSYNR1 0x%08x, GFSYNR2 0x%08x\n", > gfsr, gfsynr0, gfsynr1, gfsynr2); > + if (IS_ENABLED(CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT) && > + (gfsr & sGFSR_USF)) > + dev_err_ratelimited(smmu->dev, > + "Stream ID %hu may not be described by firmware, try booting with \"arm-smmu.disable_bypass=0\"\n", > + (u16)gfsynr1); In general it seems like a sane idea to surface an error like this. I guess a few nits: 1. "By firmware" might be a bit misleading. In most cases I'm aware of the problem is in the device tree that was bundled together with the kernel. If there are actually cases where firmware has baked in a device tree and it got this wrong then we might want to spend time figuring out what to do about it. 2. Presumably booting with "arm-smmu.disable_bypass=0" is in most cases the least desirable option available. I always consider kernel command line parameters as something of a last resort for configuration and would only be something that and end user might do if they were given a kernel compiled by someone else (like if someone where taking a prebuilt Linux distro and trying to install it onto a generic PC). Are you seeing cases where this is happening? If people are compiling their own kernel I'd argue that telling them to set "CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT" to "no" is much better than trying to jam a command line option on. Command line options don't scale well. 3. Any chance you could make it more obvious that this change is undesirable and a last resort? AKA: "Stream ID x blocked for security reasons; allow anyway by booting with arm-smmu.disable_bypass=0" -Doug
On Fri, Sep 13, 2019 at 12:48:37PM +0100, Robin Murphy wrote: > Although CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT is a welcome tool > for smoking out inadequate firmware, the failure mode is non-obvious > and can be confusing for end users. Add some special-case reporting of > Unidentified Stream Faults to help clarify this particular symptom. Having encountered this on a board that turned up this week, it may be better to use the hex representation of the stream ID, especially as it seems normal for the stream ID to be made up of implementation defined bitfields. If we want to stick with decimal, maybe masking the stream ID with the number of allowable bits would be a good idea, so that the decimal value remains meaningful should other bits be non-zero? > CC: Douglas Anderson <dianders@chromium.org> > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > --- > drivers/iommu/arm-smmu.c | 5 +++++ > drivers/iommu/arm-smmu.h | 2 ++ > 2 files changed, 7 insertions(+) > > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > index b7cf24402a94..76ac8c180695 100644 > --- a/drivers/iommu/arm-smmu.c > +++ b/drivers/iommu/arm-smmu.c > @@ -499,6 +499,11 @@ static irqreturn_t arm_smmu_global_fault(int irq, void *dev) > dev_err_ratelimited(smmu->dev, > "\tGFSR 0x%08x, GFSYNR0 0x%08x, GFSYNR1 0x%08x, GFSYNR2 0x%08x\n", > gfsr, gfsynr0, gfsynr1, gfsynr2); > + if (IS_ENABLED(CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT) && > + (gfsr & sGFSR_USF)) > + dev_err_ratelimited(smmu->dev, > + "Stream ID %hu may not be described by firmware, try booting with \"arm-smmu.disable_bypass=0\"\n", > + (u16)gfsynr1); > > arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_sGFSR, gfsr); > return IRQ_HANDLED; > diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h > index c9c13b5785f2..46f7e161e83e 100644 > --- a/drivers/iommu/arm-smmu.h > +++ b/drivers/iommu/arm-smmu.h > @@ -79,6 +79,8 @@ > #define ID7_MINOR GENMASK(3, 0) > > #define ARM_SMMU_GR0_sGFSR 0x48 > +#define sGFSR_USF BIT(2) I do wonder if this is another instance where writing "(1 << 1)" would have resulted in less chance of a mistake being made... wrapping stuff up into macros is not always better! 9.6.15 SMMU_sGFSR, Global Fault Status Register The SMMU_sGFSR bit assignments are: USF, bit[1] Unidentified stream fault. The possible values of this bit are: 0 No Unidentified stream fault. 1 Unidentified stream fault. So this wants to be: #define sGFSR_USF BIT(1)
On Fri, Sep 13, 2019 at 03:44:12PM -0700, Doug Anderson wrote: > On Fri, Sep 13, 2019 at 4:48 AM Robin Murphy <robin.murphy@arm.com> wrote: > > > > Although CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT is a welcome tool > > for smoking out inadequate firmware, the failure mode is non-obvious > > and can be confusing for end users. Add some special-case reporting of > > Unidentified Stream Faults to help clarify this particular symptom. > > > > CC: Douglas Anderson <dianders@chromium.org> > > nit that I believe that "Cc" (lowercase 2nd c) is correct. > > > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > > --- > > drivers/iommu/arm-smmu.c | 5 +++++ > > drivers/iommu/arm-smmu.h | 2 ++ > > 2 files changed, 7 insertions(+) > > > > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > > index b7cf24402a94..76ac8c180695 100644 > > --- a/drivers/iommu/arm-smmu.c > > +++ b/drivers/iommu/arm-smmu.c > > @@ -499,6 +499,11 @@ static irqreturn_t arm_smmu_global_fault(int irq, void *dev) > > dev_err_ratelimited(smmu->dev, > > "\tGFSR 0x%08x, GFSYNR0 0x%08x, GFSYNR1 0x%08x, GFSYNR2 0x%08x\n", > > gfsr, gfsynr0, gfsynr1, gfsynr2); > > + if (IS_ENABLED(CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT) && > > + (gfsr & sGFSR_USF)) > > + dev_err_ratelimited(smmu->dev, > > + "Stream ID %hu may not be described by firmware, try booting with \"arm-smmu.disable_bypass=0\"\n", > > + (u16)gfsynr1); > > In general it seems like a sane idea to surface an error like this. I > guess a few nits: > > 1. "By firmware" might be a bit misleading. In most cases I'm aware > of the problem is in the device tree that was bundled together with > the kernel. If there are actually cases where firmware has baked in a > device tree and it got this wrong then we might want to spend time > figuring out what to do about it. I thought that was usually the way UEFI systems worked, where the kernel is updated independently of the device-tree? Either way, that should be what we're aiming for, even if many platforms require the two to be tied together. > 2. Presumably booting with "arm-smmu.disable_bypass=0" is in most > cases the least desirable option available. I always consider kernel > command line parameters as something of a last resort for > configuration and would only be something that and end user might do > if they were given a kernel compiled by someone else (like if someone > where taking a prebuilt Linux distro and trying to install it onto a > generic PC). Are you seeing cases where this is happening? If people > are compiling their own kernel I'd argue that telling them to set > "CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT" to "no" is much better > than trying to jam a command line option on. Command line options > don't scale well. Hmm. Recompiling seems like even more of a last resort to me! > 3. Any chance you could make it more obvious that this change is > undesirable and a last resort? AKA: > > "Stream ID x blocked for security reasons; allow anyway by booting > with arm-smmu.disable_bypass=0" How about: "Blocked transaction from unknown Stream ID x; boot with \"arm-smmu.disable_bypass=0\" to allow these transactions, although this may have security implications." Will
Hi, On Mon, Sep 16, 2019 at 11:00 AM Will Deacon <will@kernel.org> wrote: > > On Fri, Sep 13, 2019 at 03:44:12PM -0700, Doug Anderson wrote: > > On Fri, Sep 13, 2019 at 4:48 AM Robin Murphy <robin.murphy@arm.com> wrote: > > > > > > Although CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT is a welcome tool > > > for smoking out inadequate firmware, the failure mode is non-obvious > > > and can be confusing for end users. Add some special-case reporting of > > > Unidentified Stream Faults to help clarify this particular symptom. > > > > > > CC: Douglas Anderson <dianders@chromium.org> > > > > nit that I believe that "Cc" (lowercase 2nd c) is correct. > > > > > Signed-off-by: Robin Murphy <robin.murphy@arm.com> > > > --- > > > drivers/iommu/arm-smmu.c | 5 +++++ > > > drivers/iommu/arm-smmu.h | 2 ++ > > > 2 files changed, 7 insertions(+) > > > > > > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c > > > index b7cf24402a94..76ac8c180695 100644 > > > --- a/drivers/iommu/arm-smmu.c > > > +++ b/drivers/iommu/arm-smmu.c > > > @@ -499,6 +499,11 @@ static irqreturn_t arm_smmu_global_fault(int irq, void *dev) > > > dev_err_ratelimited(smmu->dev, > > > "\tGFSR 0x%08x, GFSYNR0 0x%08x, GFSYNR1 0x%08x, GFSYNR2 0x%08x\n", > > > gfsr, gfsynr0, gfsynr1, gfsynr2); > > > + if (IS_ENABLED(CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT) && > > > + (gfsr & sGFSR_USF)) > > > + dev_err_ratelimited(smmu->dev, > > > + "Stream ID %hu may not be described by firmware, try booting with \"arm-smmu.disable_bypass=0\"\n", > > > + (u16)gfsynr1); > > > > In general it seems like a sane idea to surface an error like this. I > > guess a few nits: > > > > 1. "By firmware" might be a bit misleading. In most cases I'm aware > > of the problem is in the device tree that was bundled together with > > the kernel. If there are actually cases where firmware has baked in a > > device tree and it got this wrong then we might want to spend time > > figuring out what to do about it. > > I thought that was usually the way UEFI systems worked, where the kernel > is updated independently of the device-tree? Either way, that should be > what we're aiming for, even if many platforms require the two to be tied > together. It's my opinion that until there is a place in the kernel to "fixup" broken device trees that were baked in firmware that it's a bad idea to ship device trees separate from the kernel except if the device trees are exceedingly simple. We'll run into too many problems otherwise, either because the kernel the device tree was written for had downstream patches or someone just made a mistake in them and nobody noticed. I know device trees are supposed to be ABI, but people make mistakes and we need a way to fix them up. ...but that's getting pretty far afield from Robin's patch. > > 2. Presumably booting with "arm-smmu.disable_bypass=0" is in most > > cases the least desirable option available. I always consider kernel > > command line parameters as something of a last resort for > > configuration and would only be something that and end user might do > > if they were given a kernel compiled by someone else (like if someone > > where taking a prebuilt Linux distro and trying to install it onto a > > generic PC). Are you seeing cases where this is happening? If people > > are compiling their own kernel I'd argue that telling them to set > > "CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT" to "no" is much better > > than trying to jam a command line option on. Command line options > > don't scale well. > > Hmm. Recompiling seems like even more of a last resort to me! Depends on what you're doing. If you're not in the habit of compiling a kernel and you're just trying to make one work then the command line is great. If you're trying to manage configuration for a whole bunch of different hardware products then the command line is a terrible place to store config. ...but I guess the summary is that we wouldn't want someone to actually ship a kernel with this option on anyway. ;-) > > 3. Any chance you could make it more obvious that this change is > > undesirable and a last resort? AKA: > > > > "Stream ID x blocked for security reasons; allow anyway by booting > > with arm-smmu.disable_bypass=0" > > How about: > > "Blocked transaction from unknown Stream ID x; boot with > \"arm-smmu.disable_bypass=0\" to allow these transactions, although this > may have security implications." Fine with me if it's not too long for an error message. -Doug
On 2019-09-16 7:19 pm, Doug Anderson wrote: [...] >>> 1. "By firmware" might be a bit misleading. In most cases I'm aware >>> of the problem is in the device tree that was bundled together with >>> the kernel. If there are actually cases where firmware has baked in a >>> device tree and it got this wrong then we might want to spend time >>> figuring out what to do about it. >> >> I thought that was usually the way UEFI systems worked, where the kernel >> is updated independently of the device-tree? Either way, that should be >> what we're aiming for, even if many platforms require the two to be tied >> together. > > It's my opinion that until there is a place in the kernel to "fixup" > broken device trees that were baked in firmware that it's a bad idea > to ship device trees separate from the kernel except if the device > trees are exceedingly simple. We'll run into too many problems > otherwise, either because the kernel the device tree was written for > had downstream patches or someone just made a mistake in them and > nobody noticed. I know device trees are supposed to be ABI, but > people make mistakes and we need a way to fix them up. > > ...but that's getting pretty far afield from Robin's patch. Let's not get too hung up on devicetree - you can go out and buy certain ACPI-only platforms today that also fall foul of this, for which AFAIK the necessary firmware update is in the SoC vendor's hands. >>> 2. Presumably booting with "arm-smmu.disable_bypass=0" is in most >>> cases the least desirable option available. I always consider kernel >>> command line parameters as something of a last resort for >>> configuration and would only be something that and end user might do >>> if they were given a kernel compiled by someone else (like if someone >>> where taking a prebuilt Linux distro and trying to install it onto a >>> generic PC). Are you seeing cases where this is happening? If people >>> are compiling their own kernel I'd argue that telling them to set >>> "CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT" to "no" is much better >>> than trying to jam a command line option on. Command line options >>> don't scale well. >> >> Hmm. Recompiling seems like even more of a last resort to me! > > Depends on what you're doing. If you're not in the habit of compiling > a kernel and you're just trying to make one work then the command line > is great. If you're trying to manage configuration for a whole bunch > of different hardware products then the command line is a terrible > place to store config. > > ...but I guess the summary is that we wouldn't want someone to > actually ship a kernel with this option on anyway. ;-) FWIW the meta here is really "oops, you've just installed a new kernel and now your machine is unusable - you need to take it up with whoever supports your platform, but in the meantime this is the minimal thing you can do to get things back working as before." Personally I'm less concerned about folks maintaining "hardware products", as I'd like to assume they would hit this in QA and have a relatively short loop back to kernel people who know what's up (or at least know enough to join the dots to punt it to my inbox). My main concern is end users of SBSA-ish platforms who are free to pick and choose distros - and/or kernel packages within their distro - and thus may bugger up their machine inadvertently if the distro package happens to have picked this option up from defconfig (from a quick look at least my preferred one has). >>> 3. Any chance you could make it more obvious that this change is >>> undesirable and a last resort? AKA: >>> >>> "Stream ID x blocked for security reasons; allow anyway by booting >>> with arm-smmu.disable_bypass=0" >> >> How about: >> >> "Blocked transaction from unknown Stream ID x; boot with >> \"arm-smmu.disable_bypass=0\" to allow these transactions, although this >> may have security implications." > > Fine with me if it's not too long for an error message. Sounds good, I'll respin with a slight abbreviation of that (and minus the embarrassingly stupid thinko) tomorrow. Cheers, Robin.
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c index b7cf24402a94..76ac8c180695 100644 --- a/drivers/iommu/arm-smmu.c +++ b/drivers/iommu/arm-smmu.c @@ -499,6 +499,11 @@ static irqreturn_t arm_smmu_global_fault(int irq, void *dev) dev_err_ratelimited(smmu->dev, "\tGFSR 0x%08x, GFSYNR0 0x%08x, GFSYNR1 0x%08x, GFSYNR2 0x%08x\n", gfsr, gfsynr0, gfsynr1, gfsynr2); + if (IS_ENABLED(CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT) && + (gfsr & sGFSR_USF)) + dev_err_ratelimited(smmu->dev, + "Stream ID %hu may not be described by firmware, try booting with \"arm-smmu.disable_bypass=0\"\n", + (u16)gfsynr1); arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_sGFSR, gfsr); return IRQ_HANDLED; diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h index c9c13b5785f2..46f7e161e83e 100644 --- a/drivers/iommu/arm-smmu.h +++ b/drivers/iommu/arm-smmu.h @@ -79,6 +79,8 @@ #define ID7_MINOR GENMASK(3, 0) #define ARM_SMMU_GR0_sGFSR 0x48 +#define sGFSR_USF BIT(2) + #define ARM_SMMU_GR0_sGFSYNR0 0x50 #define ARM_SMMU_GR0_sGFSYNR1 0x54 #define ARM_SMMU_GR0_sGFSYNR2 0x58
Although CONFIG_ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT is a welcome tool for smoking out inadequate firmware, the failure mode is non-obvious and can be confusing for end users. Add some special-case reporting of Unidentified Stream Faults to help clarify this particular symptom. CC: Douglas Anderson <dianders@chromium.org> Signed-off-by: Robin Murphy <robin.murphy@arm.com> --- drivers/iommu/arm-smmu.c | 5 +++++ drivers/iommu/arm-smmu.h | 2 ++ 2 files changed, 7 insertions(+)