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

Anup Patel
2023-05-10T15:12:47Z

On Wed, May 10, 2023 at 4:18 PM Robin Murphy <robin.murphy@arm.com> 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@sifive.com>
> > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > ---
> > 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)
> > {
> > }