[PATCH v5 7/8] iommu/arm-smmu: Get associated RMR info and install bypass SMR
Jon Nettleton
jon at solid-run.com
Tue Jun 29 09:25:51 PDT 2021
On Tue, Jun 29, 2021 at 3:23 PM Robin Murphy <robin.murphy at arm.com> wrote:
>
> On 2021-06-29 08:03, Jon Nettleton wrote:
> > On Mon, Jun 14, 2021 at 12:06 PM Robin Murphy <robin.murphy at arm.com> wrote:
> >>
> >> On 2021-05-24 12:02, Shameer Kolothum 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));
> >>
> >> To reiterate, just because a bootloader/crashed kernel/whatever may have
> >> left some configuration behind doesn't mean that it matters (e.g. what
> >> if these SMRs are pointing at translation contexts?). All we should be
> >> doing here is setting the relevant RMR accommodations in our "clean
> >> slate" software state before the reset routine applies it to the
> >> hardware, just like patch #5 does for SMMUv3.
> >>
> >> Trying to safely reset an SMMU when we discover it with CLIENTPD=0 is
> >> really another issue entirely, and I'd say is beyond the scope of this
> >> series
> >>
> >>> + if (!FIELD_GET(ARM_SMMU_SMR_VALID, smr))
> >>> + continue;
> >>
> >> Note that that's not even necessarily correct (thanks to EXIDS).
> >>
> >>> + 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;
> >>
> >> This is very wrong (as has now already been pointed out).
> >>
> >>> + 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;
> >>
> >> Nit: cbndx is left uninitialised for bypass/fault entries elsewhere, so
> >> there's little point touching it here.
> >>
> >>> +
> >>> + 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;
> >>> + }
> >>
> >> If this dance is only about avoiding stream match conflicts when trying
> >> to reprogram live SMRs, simply turning the SMMU off beforehand would be
> >> a lot simpler.
> >
> > Robin,
> >
> > I am not sure what you mean here, and maybe Steve wants to jump in and
> > help clarify.
> >
> > My understanding is that "dance" is required for regions that need to
> > continue to work
> > throughout the boot process. I think the example I have seen the most
> > is for GOP drivers that
> > use system memory rather than dedicated VRAM.
>
> All that is required is to install bypass SMEs for the relevant streams
> before enabling the SMMU. That much is achieved by the
> list_for_each_entry(e, &rmr_list, list) loop setting up initial state
> followed by arm_smmu_device_reset(). The "dance" I'm referring to is the
> additional reading out of (possibly nonsense) SMR state beforehand to
> pre-bias the SMR allocator, then trying to clean up the remnants afterwards.
>
> If we're going to pretend to be robust against finding the SMMU already
> enabled *with* live traffic ongoing, there's frankly an awful lot more
> care we'd need to take beyond here (and for some aspects there's still
> no right answer). If on the other hand we're implicitly assuming that
> any boot-time enabled SMRs exactly match the RMR configuration anyway,
> then simply disabling the SMMU until we enable it again in the reset
> routine still preserves the necessary bypass behaviour for RMR streams
> while sidestepping any issues related to reprogramming live SMMU state.
>
> Robin.
>
> >>> + }
> >>> +
> >>> + 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);
> >>>
> >>>
Shameer,
Sorry for the delays. Here is a diff of the changes that should
address the issues pointed out by Robin,
I have tested that this works as expected on my HoneyComb LX2160A.
diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c
b/drivers/iommu/arm/arm-smmu/arm-smmu.c
index ab7b9db77625..a358bd326d0b 100644
--- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
+++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
@@ -2068,29 +2068,21 @@ 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);
+ /* Rather than trying to look at existing mappings that
+ * are setup by the firmware and then invalidate the ones
+ * that do no have matching RMR entries, just disable the
+ * SMMU until it gets enabled again in the reset routine.
+ */
- 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;
- }
- }
+ reg = arm_smmu_gr0_read(smmu, ARM_SMMU_GR0_sCR0);
+ reg &= ~ARM_SMMU_sCR0_CLIENTPD;
+ arm_smmu_gr0_write(smmu, ARM_SMMU_GR0_sCR0, reg);
list_for_each_entry(e, &rmr_list, list) {
u32 sid = e->fw_data.rmr.sid;
@@ -2100,25 +2092,16 @@ 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++;
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);
Please include that in your next patch series. Let me know if you
want me to send you the patch direct
off the list.
Thanks,
Jon
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