[PATCH v5 7/8] iommu/arm-smmu: Get associated RMR info and install bypass SMR
Jon Nettleton
jon at solid-run.com
Sun Jun 13 00:40:50 PDT 2021
On Thu, Jun 3, 2021 at 1:51 PM Jon Nettleton <jon at solid-run.com> wrote:
>
> On Thu, Jun 3, 2021 at 1:27 PM Steven Price <steven.price at arm.com> wrote:
> >
> > On 03/06/2021 09:52, Jon Nettleton wrote:
> > > On Mon, May 24, 2021 at 1:04 PM Shameer Kolothum
> > > <shameerali.kolothum.thodi at huawei.com> wrote:
> > >>
> > >> From: Jon Nettleton <jon at solid-run.com>
> > >>
> > >> Check if there is any RMR info associated with the devices behind
> > >> the SMMU and if any, install bypass SMRs for them. This is to
> > >> keep any ongoing traffic associated with these devices alive
> > >> when we enable/reset SMMU during probe().
> > >>
> > >> Signed-off-by: Jon Nettleton <jon at solid-run.com>
> > >> Signed-off-by: Steven Price <steven.price at arm.com>
> > >> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi at huawei.com>
> > >> ---
> > >> drivers/iommu/arm/arm-smmu/arm-smmu.c | 65 +++++++++++++++++++++++++++
> > >> 1 file changed, 65 insertions(+)
> > >>
> > >> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > >> index 6f72c4d208ca..56db3d3238fc 100644
> > >> --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > >> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > >> @@ -2042,6 +2042,67 @@ err_reset_platform_ops: __maybe_unused;
> > >> return err;
> > >> }
> > >>
> > >> +static void arm_smmu_rmr_install_bypass_smr(struct arm_smmu_device *smmu)
> > >> +{
> > >> + struct list_head rmr_list;
> > >> + struct iommu_resv_region *e;
> > >> + int i, cnt = 0;
> > >> + u32 smr;
> > >> + u32 reg;
> > >> +
> > >> + INIT_LIST_HEAD(&rmr_list);
> > >> + if (iommu_dma_get_rmrs(dev_fwnode(smmu->dev), &rmr_list))
> > >> + return;
> > >> +
> > >> + reg = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_sCR0);
> > >> +
> > >> + if ((reg & ARM_SMMU_sCR0_USFCFG) && !(reg & ARM_SMMU_sCR0_CLIENTPD)) {
> > >> + /*
> > >> + * SMMU is already enabled and disallowing bypass, so preserve
> > >> + * the existing SMRs
> > >> + */
> > >> + for (i = 0; i < smmu->num_mapping_groups; i++) {
> > >> + smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
> > >> + if (!FIELD_GET(ARM_SMMU_SMR_VALID, smr))
> > >> + continue;
> > >> + smmu->smrs[i].id = FIELD_GET(ARM_SMMU_SMR_ID, smr);
> > >> + smmu->smrs[i].mask = FIELD_GET(ARM_SMMU_SMR_MASK, smr);
> > >> + smmu->smrs[i].valid = true;
> > >> + }
> > >> + }
> > >> +
> > >> + list_for_each_entry(e, &rmr_list, list) {
> > >> + u32 sid = e->fw_data.rmr.sid;
> > >> +
> > >> + i = arm_smmu_find_sme(smmu, sid, ~0);
> > >> + if (i < 0)
> > >> + continue;
> > >> + if (smmu->s2crs[i].count == 0) {
> > >> + smmu->smrs[i].id = sid;
> > >> + smmu->smrs[i].mask = ~0;
> >
> > Looking at this code again, that mask looks wrong! According to the SMMU
> > spec MASK[i]==1 means ID[i] is ignored. I.e. this means completely
> > ignore the ID...
> >
> > I'm not at all sure why they designed the hardware that way round.
> >
> > >> + smmu->smrs[i].valid = true;
> > >> + }
> > >> + smmu->s2crs[i].count++;
> > >> + smmu->s2crs[i].type = S2CR_TYPE_BYPASS;
> > >> + smmu->s2crs[i].privcfg = S2CR_PRIVCFG_DEFAULT;
> > >> + smmu->s2crs[i].cbndx = 0xff;
> > >> +
> > >> + cnt++;
> > >> + }
> > >> +
> > >> + if ((reg & ARM_SMMU_sCR0_USFCFG) && !(reg & ARM_SMMU_sCR0_CLIENTPD)) {
> > >> + /* Remove the valid bit for unused SMRs */
> > >> + for (i = 0; i < smmu->num_mapping_groups; i++) {
> > >> + if (smmu->s2crs[i].count == 0)
> > >> + smmu->smrs[i].valid = false;
> > >> + }
> > >> + }
> > >> +
> > >> + dev_notice(smmu->dev, "\tpreserved %d boot mapping%s\n", cnt,
> > >> + cnt == 1 ? "" : "s");
> > >> + iommu_dma_put_rmrs(dev_fwnode(smmu->dev), &rmr_list);
> > >> +}
> > >> +
> > >> static int arm_smmu_device_probe(struct platform_device *pdev)
> > >> {
> > >> struct resource *res;
> > >> @@ -2168,6 +2229,10 @@ static int arm_smmu_device_probe(struct platform_device *pdev)
> > >> }
> > >>
> > >> platform_set_drvdata(pdev, smmu);
> > >> +
> > >> + /* Check for RMRs and install bypass SMRs if any */
> > >> + arm_smmu_rmr_install_bypass_smr(smmu);
> > >> +
> > >> arm_smmu_device_reset(smmu);
> > >> arm_smmu_test_smr_masks(smmu);
> > >>
> > >> --
> > >> 2.17.1
> > >>
> > >
> > > Shameer and Robin
> > >
> > > I finally got around to updating edk2 and the HoneyComb IORT tables to
> > > reflect the new standards.
> > > Out of the box the new patchset was generating errors immediatly after
> > > the smmu bringup.
> > >
> > > arm-smmu arm-smmu.0.auto: Unhandled context fault: fsr=0x402, iova=0x2080000140,
> > > fsynr=0x1d0040, cbfrsynra=0x4000, cb=0
> > >
> > > These errors were generated even with disable_bypass=0
> > >
> > > I tracked down the issue to
> > >
> > > This code is skipped as Robin said would be correct
> >
> > If you're skipping the first bit of code, then that (hopefully) means
> > that the SMMU is disabled...
> >
> > >> + if ((reg & ARM_SMMU_sCR0_USFCFG) && !(reg & ARM_SMMU_sCR0_CLIENTPD)) {
> > >> + /*
> > >> + * SMMU is already enabled and disallowing bypass, so preserve
> > >> + * the existing SMRs
> > >> + */
> > >> + for (i = 0; i < smmu->num_mapping_groups; i++) {
> > >> + smr = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_SMR(i));
> > >> + if (!FIELD_GET(ARM_SMMU_SMR_VALID, smr))
> > >> + continue;
> > >> + smmu->smrs[i].id = FIELD_GET(ARM_SMMU_SMR_ID, smr);
> > >> + smmu->smrs[i].mask = FIELD_GET(ARM_SMMU_SMR_MASK, smr);
> > >> + smmu->smrs[i].valid = true;
> > >> + }[ 2.707729] arm-smmu: setting up rmr list on 0x4000
> > > [ 2.712598] arm-smmu: s2crs count is 0 smrs index 0x0
> > > [ 2.717638] arm-smmu: s2crs count is 0 smrs id is 0x4000
> > > [ 2.722939] arm-smmu: s2crs count is 0 smrs mask is 0x8000
> > > [ 2.728417] arm-smmu arm-smmu.0.auto: preserved 1 boot mapping
> > >
> > >> + }
> > >
> > > Then this code block was hit which is correct
> > >
> > >> + if (smmu->s2crs[i].count == 0) {
> > >> + smmu->smrs[i].id = sid;
> > >> + smmu->smrs[i].mask = ~0;
> > >> + smmu->smrs[i].valid = true;
> > >> + }
> > >
> > > The mask was causing the issue. If I think ammended that segment to read
> > > the mask as setup by the hardware everything was back to functioning both
> > > with and without disable_bypass set.
> >
> > ...so reading a mask from it doesn't sounds quite right.
> >
> > Can you have a go with a corrected mask of '0' rather than all-1s and
> > see if that helps? My guess is that the mask of ~0 was causing multiple
> > matches in the SMRs which is 'UNPREDICTABLE'.
> >
> > Sadly in my test setup there's only the one device behind the SMMU so
> > I didn't spot this (below patch works for me, but that's not saying
> > much).
> >
> > Steve
> >
> > --->8---
> > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > index 56db3d3238fc..44831d0c78e4 100644
> > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > @@ -2079,7 +2079,7 @@ static void arm_smmu_rmr_install_bypass_smr(struct arm_smmu_device *smmu)
> > continue;
> > if (smmu->s2crs[i].count == 0) {
> > smmu->smrs[i].id = sid;
> > - smmu->smrs[i].mask = ~0;
> > + smmu->smrs[i].mask = 0;
> > smmu->smrs[i].valid = true;
> > }
> > smmu->s2crs[i].count++;
>
> Yes this works fine. Thanks
Shameer,
Can you pick up this change into your next patch set? Also are there
any objections to adding this to the SMMUv2 code from the maintainers?
-Jon
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