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

Robin Murphy
2023-05-10T10:48:53Z

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.

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)
> {
> }