Re: [PATCH v3 07/11] irqchip/riscv-imsic: Improve IOMMU DMA support

[Anup Patel]

On Wed, May 10, 2023 at 4:18 PM Robin Murphy <robin.murphy@xxxxxxx> wrote:
>
> On 2023-05-08 15:28, Anup Patel wrote:
> > We have a separate RISC-V IMSIC MSI address for each CPU so changing
> > MSI (or IRQ) affinity results in re-programming of MSI address in
> > the PCIe (or platform) device.
> >
> > Currently, the iommu_dma_prepare_msi() is called only once at the
> > time of IRQ allocation so IOMMU DMA domain will only have mapping
> > for one MSI page. This means iommu_dma_compose_msi_msg() called
> > by imsic_irq_compose_msi_msg() will always use the same MSI page
> > irrespective to target CPU MSI address. In other words, changing
> > MSI (or IRQ) affinity for device using IOMMU DMA domain will not
> > work.
> >
> > To address above issue, we do the following:
> > 1) Map MSI pages for all CPUs in imsic_irq_domain_alloc()
> >     using iommu_dma_prepare_msi().
> > 2) Add a new iommu_dma_select_msi() API to select a specific
> >     MSI page from a set of already mapped MSI pages.
> > 3) Use iommu_dma_select_msi() to select a specific MSI page
> >     before calling iommu_dma_compose_msi_msg() in
> >     imsic_irq_compose_msi_msg().
>
> The high-level design is that prepare ensures any necessary page
> mappings exist, then compose retrieves the appropriate page for the
> given message. I think it generalises well enough without needing a new
> op, it just means that caching a single page in the msi_desc up-front no
> longer fits, so that wants tweaking to allow compose to do a more
> general lookup.

Yes, usage of msi_desc_get/set_iommu_cookie() is the only problem.

To have minimal impact on other irqchip drivers, I added a separate
iommu_dma_select_msi() API but in the next patch revision I will
tweak iommu_dma_compose_msi_msg() to lookup msi_page based
on the existing MSI address in "struct msi_msg".

Regards,
Anup

>
> Thanks,
> Robin.
>
> > Reported-by: Vincent Chen <vincent.chen@xxxxxxxxxx>
> > Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/iommu/dma-iommu.c         | 38 +++++++++++++++++++++++++++++++
> >   drivers/irqchip/irq-riscv-imsic.c | 27 ++++++++++++----------
> >   include/linux/iommu.h             |  6 +++++
> >   3 files changed, 59 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> > index 7a9f0b0bddbd..07782c77a6eb 100644
> > --- a/drivers/iommu/dma-iommu.c
> > +++ b/drivers/iommu/dma-iommu.c
> > @@ -1677,6 +1677,44 @@ int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr)
> >       return 0;
> >   }
> >
> > +/**
> > + * iommu_dma_select_msi() - Select a MSI page from a set of
> > + * already mapped MSI pages in the IOMMU domain.
> > + *
> > + * @desc: MSI descriptor prepared by iommu_dma_prepare_msi()
> > + * @msi_addr: physical address of the MSI page to be selected
> > + *
> > + * Return: 0 on success or negative error code if the select failed.
> > + */
> > +int iommu_dma_select_msi(struct msi_desc *desc, phys_addr_t msi_addr)
> > +{
> > +     struct device *dev = msi_desc_to_dev(desc);
> > +     struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> > +     const struct iommu_dma_msi_page *msi_page;
> > +     struct iommu_dma_cookie *cookie;
> > +
> > +     if (!domain || !domain->iova_cookie) {
> > +             desc->iommu_cookie = NULL;
> > +             return 0;
> > +     }
> > +
> > +     cookie = domain->iova_cookie;
> > +     msi_addr &= ~(phys_addr_t)(cookie_msi_granule(cookie) - 1);
> > +
> > +     msi_page = msi_desc_get_iommu_cookie(desc);
> > +     if (msi_page && msi_page->phys == msi_addr)
> > +             return 0;
> > +
> > +     list_for_each_entry(msi_page, &cookie->msi_page_list, list) {
> > +             if (msi_page->phys == msi_addr) {
> > +                     msi_desc_set_iommu_cookie(desc, msi_page);
> > +                     return 0;
> > +             }
> > +     }
> > +
> > +     return -ENOENT;
> > +}
> > +
> >   /**
> >    * iommu_dma_compose_msi_msg() - Apply translation to an MSI message
> >    * @desc: MSI descriptor prepared by iommu_dma_prepare_msi()
> > diff --git a/drivers/irqchip/irq-riscv-imsic.c b/drivers/irqchip/irq-riscv-imsic.c
> > index 30247c84a6b0..ec61c599e0c5 100644
> > --- a/drivers/irqchip/irq-riscv-imsic.c
> > +++ b/drivers/irqchip/irq-riscv-imsic.c
> > @@ -446,6 +446,10 @@ static void imsic_irq_compose_msi_msg(struct irq_data *d,
> >       if (WARN_ON(err))
> >               return;
> >
> > +     err = iommu_dma_select_msi(desc, msi_addr);
> > +     if (WARN_ON(err))
> > +             return;
> > +
> >       msg->address_hi = upper_32_bits(msi_addr);
> >       msg->address_lo = lower_32_bits(msi_addr);
> >       msg->data = d->hwirq;
> > @@ -493,11 +497,18 @@ static int imsic_irq_domain_alloc(struct irq_domain *domain,
> >       int i, hwirq, err = 0;
> >       unsigned int cpu;
> >
> > -     err = imsic_get_cpu(&imsic->lmask, false, &cpu);
> > -     if (err)
> > -             return err;
> > +     /* Map MSI address of all CPUs */
> > +     for_each_cpu(cpu, &imsic->lmask) {
> > +             err = imsic_cpu_page_phys(cpu, 0, &msi_addr);
> > +             if (err)
> > +                     return err;
> >
> > -     err = imsic_cpu_page_phys(cpu, 0, &msi_addr);
> > +             err = iommu_dma_prepare_msi(info->desc, msi_addr);
> > +             if (err)
> > +                     return err;
> > +     }
> > +
> > +     err = imsic_get_cpu(&imsic->lmask, false, &cpu);
> >       if (err)
> >               return err;
> >
> > @@ -505,10 +516,6 @@ static int imsic_irq_domain_alloc(struct irq_domain *domain,
> >       if (hwirq < 0)
> >               return hwirq;
> >
> > -     err = iommu_dma_prepare_msi(info->desc, msi_addr);
> > -     if (err)
> > -             goto fail;
> > -
> >       for (i = 0; i < nr_irqs; i++) {
> >               imsic_id_set_target(hwirq + i, cpu);
> >               irq_domain_set_info(domain, virq + i, hwirq + i,
> > @@ -528,10 +535,6 @@ static int imsic_irq_domain_alloc(struct irq_domain *domain,
> >       }
> >
> >       return 0;
> > -
> > -fail:
> > -     imsic_ids_free(hwirq, get_count_order(nr_irqs));
> > -     return err;
> >   }
> >
> >   static void imsic_irq_domain_free(struct irq_domain *domain,
> > diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> > index e8c9a7da1060..41e8613832ab 100644
> > --- a/include/linux/iommu.h
> > +++ b/include/linux/iommu.h
> > @@ -1117,6 +1117,7 @@ void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 dma_limit);
> >   int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base);
> >
> >   int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr);
> > +int iommu_dma_select_msi(struct msi_desc *desc, phys_addr_t msi_addr);
> >   void iommu_dma_compose_msi_msg(struct msi_desc *desc, struct msi_msg *msg);
> >
> >   #else /* CONFIG_IOMMU_DMA */
> > @@ -1138,6 +1139,11 @@ static inline int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_a
> >       return 0;
> >   }
> >
> > +static inline int iommu_dma_select_msi(struct msi_desc *desc, phys_addr_t msi_addr)
> > +{
> > +     return 0;
> > +}
> > +
> >   static inline void iommu_dma_compose_msi_msg(struct msi_desc *desc, struct msi_msg *msg)
> >   {
> >   }