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 <20200626200414.14382-2-jcrouse@codeaurora.org> <9943752c-9e0b-3d11-cba9-ee579d449e30@arm.com>
In-Reply-To: <9943752c-9e0b-3d11-cba9-ee579d449e30@arm.com>
From:   Rob Clark <robdclark@gmail.com>
Date:   Tue, 7 Jul 2020 08:09:41 -0700
Message-ID: <CAF6AEGvZ+HSwvf+N=fYjkB6FKfFSVPM5G6QqkFh8NOT6d2urgw@mail.gmail.com>
Subject: Re: [Freedreno] [PATCH v2 1/6] iommu/arm-smmu: Add auxiliary domain
 support for arm-smmuv2
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     Jordan Crouse <jcrouse@codeaurora.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Will Deacon <will@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>, Joerg
        Roedel <joro@8bytes.org>," <iommu@lists.linux-foundation.org>,
        John Stultz <john.stultz@linaro.org>,
        freedreno <freedreno@lists.freedesktop.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Jul 7, 2020 at 5:34 AM Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 2020-06-26 21:04, Jordan Crouse wrote:
> > Support auxiliary domains for arm-smmu-v2 to initialize and support
> > multiple pagetables for a single SMMU context bank. Since the smmu-v2
> > hardware doesn't have any built in support for switching the pagetable
> > base it is left as an exercise to the caller to actually use the pagetable.
>
> Hmm, I've still been thinking that we could model this as supporting
> exactly 1 aux domain iff the device is currently attached to a primary
> domain with TTBR1 enabled. Then supporting multiple aux domains with
> magic TTBR0 switching is the Adreno-specific extension on top of that.
>
> And if we don't want to go to that length, then - as I think Will was
> getting at - I'm not sure it's worth bothering at all. There doesn't
> seem to be any point in half-implementing a pretend aux domain interface
> while still driving a bus through the rest of the abstractions - it's
> really the worst of both worlds. If we're going to hand over the guts of
> io-pgtable to the GPU driver then couldn't it just use
> DOMAIN_ATTR_PGTABLE_CFG bidirectionally to inject a TTBR0 table straight
> into the TTBR1-ified domain?

So, something along the lines of:

1) qcom_adreno_smmu_impl somehow tells core arms-smmu that we want
   to use TTBR1 instead of TTBR0

2) gpu driver uses iommu_domain_get_attr(PGTABLE_CFG) to snapshot
   the initial pgtable cfg.  (Btw, I kinda feel like we should add
   io_pgtable_fmt to io_pgtable_cfg to make it self contained.)

3) gpu driver constructs pgtable_ops for TTBR0, and then kicks
   arm-smmu to do the initial setup to enable TTBR0 with
   iommu_domain_set_attr(PGTABLE_CFG, &ttbr0_pgtable_cfg)

if I understood you properly, that sounds simpler.

> Much as I like the idea of the aux domain abstraction and making this
> fit semi-transparently into the IOMMU API, if an almost entirely private
> interface will be the simplest and cleanest way to get it done then at
> this point also I'm starting to lean towards just getting it done. But
> if some other mediated-device type case then turns up that doesn't quite
> fit that private interface, we revisit the proper abstraction again and
> I reserve the right to say "I told you so" ;)

I'm on board with not trying to design this too generically until
there is a second user

BR,
-R


>
> Robin.
>
> > Aux domains are supported if split pagetable (TTBR1) support has been
> > enabled on the master domain.  Each auxiliary domain will reuse the
> > configuration of the master domain. By default the a domain with TTBR1
> > support will have the TTBR0 region disabled so the first attached aux
> > domain will enable the TTBR0 region in the hardware and conversely the
> > last domain to be detached will disable TTBR0 translations.  All subsequent
> > auxiliary domains create a pagetable but not touch the hardware.
> >
> > The leaf driver will be able to query the physical address of the
> > pagetable with the DOMAIN_ATTR_PTBASE attribute so that it can use the
> > address with whatever means it has to switch the pagetable base.
> >
> > Following is a pseudo code example of how a domain can be created
> >
> >   /* Check to see if aux domains are supported */
> >   if (iommu_dev_has_feature(dev, IOMMU_DEV_FEAT_AUX)) {
> >        iommu = iommu_domain_alloc(...);
> >
> >        if (iommu_aux_attach_device(domain, dev))
> >                return FAIL;
> >
> >       /* Save the base address of the pagetable for use by the driver
> >       iommu_domain_get_attr(domain, DOMAIN_ATTR_PTBASE, &ptbase);
> >   }
> >
> > Then 'domain' can be used like any other iommu domain to map and
> > unmap iova addresses in the pagetable.
> >
> > Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
> > ---
> >
> >   drivers/iommu/arm-smmu.c | 219 ++++++++++++++++++++++++++++++++++++---
> >   drivers/iommu/arm-smmu.h |   1 +
> >   2 files changed, 204 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> > index 060139452c54..ce6d654301bf 100644
> > --- a/drivers/iommu/arm-smmu.c
> > +++ b/drivers/iommu/arm-smmu.c
> > @@ -91,6 +91,7 @@ struct arm_smmu_cb {
> >       u32                             tcr[2];
> >       u32                             mair[2];
> >       struct arm_smmu_cfg             *cfg;
> > +     atomic_t                        aux;
> >   };
> >
> >   struct arm_smmu_master_cfg {
> > @@ -667,6 +668,86 @@ static void arm_smmu_write_context_bank(struct arm_smmu_device *smmu, int idx)
> >       arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_SCTLR, reg);
> >   }
> >
> > +/*
> > + * Update the context context bank to enable TTBR0. Assumes AARCH64 S1
> > + * configuration.
> > + */
> > +static void arm_smmu_context_set_ttbr0(struct arm_smmu_cb *cb,
> > +             struct io_pgtable_cfg *pgtbl_cfg)
> > +{
> > +     u32 tcr = cb->tcr[0];
> > +
> > +     /* Add the TCR configuration from the new pagetable config */
> > +     tcr |= arm_smmu_lpae_tcr(pgtbl_cfg);
> > +
> > +     /* Make sure that both TTBR0 and TTBR1 are enabled */
> > +     tcr &= ~(ARM_SMMU_TCR_EPD0 | ARM_SMMU_TCR_EPD1);
> > +
> > +     /* Udate the TCR register */
> > +     cb->tcr[0] = tcr;
> > +
> > +     /* Program the new TTBR0 */
> > +     cb->ttbr[0] = pgtbl_cfg->arm_lpae_s1_cfg.ttbr;
> > +     cb->ttbr[0] |= FIELD_PREP(ARM_SMMU_TTBRn_ASID, cb->cfg->asid);
> > +}
> > +
> > +/*
> > + * Thus function assumes that the current model only allows aux domains for
> > + * AARCH64 S1 configurations
> > + */
> > +static int arm_smmu_aux_init_domain_context(struct iommu_domain *domain,
> > +             struct arm_smmu_device *smmu, struct arm_smmu_cfg *master)
> > +{
> > +     struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> > +     struct io_pgtable_ops *pgtbl_ops;
> > +     struct io_pgtable_cfg pgtbl_cfg;
> > +
> > +     mutex_lock(&smmu_domain->init_mutex);
> > +
> > +     /* Copy the configuration from the master */
> > +     memcpy(&smmu_domain->cfg, master, sizeof(smmu_domain->cfg));
> > +
> > +     smmu_domain->flush_ops = &arm_smmu_s1_tlb_ops;
> > +     smmu_domain->smmu = smmu;
> > +
> > +     pgtbl_cfg = (struct io_pgtable_cfg) {
> > +             .pgsize_bitmap = smmu->pgsize_bitmap,
> > +             .ias = smmu->va_size,
> > +             .oas = smmu->ipa_size,
> > +             .coherent_walk = smmu->features & ARM_SMMU_FEAT_COHERENT_WALK,
> > +             .tlb = smmu_domain->flush_ops,
> > +             .iommu_dev = smmu->dev,
> > +             .quirks = 0,
> > +     };
> > +
> > +     if (smmu_domain->non_strict)
> > +             pgtbl_cfg.quirks |= IO_PGTABLE_QUIRK_NON_STRICT;
> > +
> > +     pgtbl_ops = alloc_io_pgtable_ops(ARM_64_LPAE_S1, &pgtbl_cfg,
> > +             smmu_domain);
> > +     if (!pgtbl_ops) {
> > +             mutex_unlock(&smmu_domain->init_mutex);
> > +             return -ENOMEM;
> > +     }
> > +
> > +     domain->pgsize_bitmap = pgtbl_cfg.pgsize_bitmap;
> > +
> > +     domain->geometry.aperture_end = (1UL << smmu->va_size) - 1;
> > +     domain->geometry.force_aperture = true;
> > +
> > +     /* enable TTBR0 when the the first aux domain is attached */
> > +     if (atomic_inc_return(&smmu->cbs[master->cbndx].aux) == 1) {
> > +             arm_smmu_context_set_ttbr0(&smmu->cbs[master->cbndx],
> > +                     &pgtbl_cfg);
> > +             arm_smmu_write_context_bank(smmu, master->cbndx);
> > +     }
> > +
> > +     smmu_domain->pgtbl_ops = pgtbl_ops;
> > +     mutex_unlock(&smmu_domain->init_mutex);
> > +
> > +     return 0;
> > +}
> > +
> >   static int arm_smmu_init_domain_context(struct iommu_domain *domain,
> >                                       struct arm_smmu_device *smmu,
> >                                       struct device *dev)
> > @@ -871,36 +952,70 @@ static int arm_smmu_init_domain_context(struct iommu_domain *domain,
> >       return ret;
> >   }
> >
> > +static void
> > +arm_smmu_destroy_aux_domain_context(struct arm_smmu_domain *smmu_domain)
> > +{
> > +     struct arm_smmu_device *smmu = smmu_domain->smmu;
> > +     struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
> > +     int ret;
> > +
> > +     /*
> > +      * If this is the last aux domain to be freed, disable TTBR0 by turning
> > +      * off translations and clearing TTBR0
> > +      */
> > +     if (atomic_dec_return(&smmu->cbs[cfg->cbndx].aux) == 0) {
> > +             /* Clear out the T0 region */
> > +             smmu->cbs[cfg->cbndx].tcr[0] &= ~GENMASK(15, 0);
> > +             /* Disable TTBR0 translations */
> > +             smmu->cbs[cfg->cbndx].tcr[0] |= ARM_SMMU_TCR_EPD0;
> > +             /* Clear the TTBR0 pagetable address */
> > +             smmu->cbs[cfg->cbndx].ttbr[0] =
> > +                     FIELD_PREP(ARM_SMMU_TTBRn_ASID, cfg->asid);
> > +
> > +             ret = arm_smmu_rpm_get(smmu);
> > +             if (!ret) {
> > +                     arm_smmu_write_context_bank(smmu, cfg->cbndx);
> > +                     arm_smmu_rpm_put(smmu);
> > +             }
> > +     }
> > +
> > +}
> > +
> >   static void arm_smmu_destroy_domain_context(struct iommu_domain *domain)
> >   {
> >       struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> >       struct arm_smmu_device *smmu = smmu_domain->smmu;
> >       struct arm_smmu_cfg *cfg = &smmu_domain->cfg;
> > -     int ret, irq;
> >
> >       if (!smmu || domain->type == IOMMU_DOMAIN_IDENTITY)
> >               return;
> >
> > -     ret = arm_smmu_rpm_get(smmu);
> > -     if (ret < 0)
> > -             return;
> > +     if (smmu_domain->aux)
> > +             arm_smmu_destroy_aux_domain_context(smmu_domain);
> >
> > -     /*
> > -      * Disable the context bank and free the page tables before freeing
> > -      * it.
> > -      */
> > -     smmu->cbs[cfg->cbndx].cfg = NULL;
> > -     arm_smmu_write_context_bank(smmu, cfg->cbndx);
> > +     /* Check if the last user is done with the context bank */
> > +     if (atomic_read(&smmu->cbs[cfg->cbndx].aux) == 0) {
> > +             int ret = arm_smmu_rpm_get(smmu);
> > +             int irq;
> >
> > -     if (cfg->irptndx != ARM_SMMU_INVALID_IRPTNDX) {
> > -             irq = smmu->irqs[smmu->num_global_irqs + cfg->irptndx];
> > -             devm_free_irq(smmu->dev, irq, domain);
> > +             if (ret < 0)
> > +                     return;
> > +
> > +             /* Disable the context bank */
> > +             smmu->cbs[cfg->cbndx].cfg = NULL;
> > +             arm_smmu_write_context_bank(smmu, cfg->cbndx);
> > +
> > +             if (cfg->irptndx != ARM_SMMU_INVALID_IRPTNDX) {
> > +                     irq = smmu->irqs[smmu->num_global_irqs + cfg->irptndx];
> > +                     devm_free_irq(smmu->dev, irq, domain);
> > +             }
> > +
> > +             __arm_smmu_free_bitmap(smmu->context_map, cfg->cbndx);
> > +             arm_smmu_rpm_put(smmu);
> >       }
> >
> > +     /* Destroy the pagetable */
> >       free_io_pgtable_ops(smmu_domain->pgtbl_ops);
> > -     __arm_smmu_free_bitmap(smmu->context_map, cfg->cbndx);
> > -
> > -     arm_smmu_rpm_put(smmu);
> >   }
> >
> >   static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
> > @@ -1161,6 +1276,74 @@ static int arm_smmu_domain_add_master(struct arm_smmu_domain *smmu_domain,
> >       return 0;
> >   }
> >
> > +static bool arm_smmu_dev_has_feat(struct device *dev,
> > +             enum iommu_dev_features feat)
> > +{
> > +     if (feat != IOMMU_DEV_FEAT_AUX)
> > +             return false;
> > +
> > +     return true;
> > +}
> > +
> > +static int arm_smmu_dev_enable_feat(struct device *dev,
> > +             enum iommu_dev_features feat)
> > +{
> > +     /* aux domain support is always available */
> > +     if (feat == IOMMU_DEV_FEAT_AUX)
> > +             return 0;
> > +
> > +     return -ENODEV;
> > +}
> > +
> > +static int arm_smmu_dev_disable_feat(struct device *dev,
> > +             enum iommu_dev_features feat)
> > +{
> > +     return -EBUSY;
> > +}
> > +
> > +static int arm_smmu_aux_attach_dev(struct iommu_domain *domain,
> > +             struct device *dev)
> > +{
> > +     struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> > +     struct arm_smmu_master_cfg *cfg = dev_iommu_priv_get(dev);
> > +     struct arm_smmu_device *smmu = cfg->smmu;
> > +     struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> > +     struct arm_smmu_cb *cb;
> > +     int idx, i, ret, cbndx = -1;
> > +
> > +     /* Try to find the context bank configured for this device */
> > +     for_each_cfg_sme(cfg, fwspec, i, idx) {
> > +             if (idx != INVALID_SMENDX) {
> > +                     cbndx = smmu->s2crs[idx].cbndx;
> > +                     break;
> > +             }
> > +     }
> > +
> > +     if (cbndx == -1)
> > +             return -ENODEV;
> > +
> > +     cb = &smmu->cbs[cbndx];
> > +
> > +     /* Aux domains are only supported for AARCH64 configurations */
> > +     if (cb->cfg->fmt != ARM_SMMU_CTX_FMT_AARCH64)
> > +             return -EINVAL;
> > +
> > +     /* Make sure that TTBR1 is enabled in the hardware */
> > +     if ((cb->tcr[0] & ARM_SMMU_TCR_EPD1))
> > +             return -EINVAL;
> > +
> > +     smmu_domain->aux = true;
> > +
> > +     ret = arm_smmu_rpm_get(smmu);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = arm_smmu_aux_init_domain_context(domain, smmu, cb->cfg);
> > +
> > +     arm_smmu_rpm_put(smmu);
> > +     return ret;
> > +}
> > +
> >   static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
> >   {
> >       struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> > @@ -1653,6 +1836,10 @@ static struct iommu_ops arm_smmu_ops = {
> >       .get_resv_regions       = arm_smmu_get_resv_regions,
> >       .put_resv_regions       = generic_iommu_put_resv_regions,
> >       .def_domain_type        = arm_smmu_def_domain_type,
> > +     .dev_has_feat           = arm_smmu_dev_has_feat,
> > +     .dev_enable_feat        = arm_smmu_dev_enable_feat,
> > +     .dev_disable_feat       = arm_smmu_dev_disable_feat,
> > +     .aux_attach_dev         = arm_smmu_aux_attach_dev,
> >       .pgsize_bitmap          = -1UL, /* Restricted during device attach */
> >   };
> >
> > diff --git a/drivers/iommu/arm-smmu.h b/drivers/iommu/arm-smmu.h
> > index c417814f1d98..79d441024043 100644
> > --- a/drivers/iommu/arm-smmu.h
> > +++ b/drivers/iommu/arm-smmu.h
> > @@ -346,6 +346,7 @@ struct arm_smmu_domain {
> >       spinlock_t                      cb_lock; /* Serialises ATS1* ops and TLB syncs */
> >       struct iommu_domain             domain;
> >       struct device                   *dev;   /* Device attached to this domain */
> > +     bool                            aux;
> >   };
> >
> >   static inline u32 arm_smmu_lpae_tcr(struct io_pgtable_cfg *cfg)
> >
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