Messages in this thread | | | Subject | Re: [PATCH 2/7] iommu/dma-iommu: Split iommu_dma_map_msi_msg in two parts | From | Julien Grall <> | Date | Mon, 29 Apr 2019 14:14:18 +0100 |
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Hi Marc,
On 23/04/2019 11:54, Marc Zyngier wrote: > On 18/04/2019 18:26, Julien Grall wrote: >> On RT, the function iommu_dma_map_msi_msg may be called from >> non-preemptible context. This will lead to a splat with >> CONFIG_DEBUG_ATOMIC_SLEEP as the function is using spin_lock >> (they can sleep on RT). >> >> The function iommu_dma_map_msi_msg is used to map the MSI page in the >> IOMMU PT and update the MSI message with the IOVA. >> >> Only the part to lookup for the MSI page requires to be called in >> preemptible context. As the MSI page cannot change over the lifecycle >> of the MSI interrupt, the lookup can be cached and re-used later on. >> >> This patch split the function iommu_dma_map_msi_msg in two new >> functions: >> - iommu_dma_prepare_msi: This function will prepare the mapping in >> the IOMMU and store the cookie in the structure msi_desc. This >> function should be called in preemptible context. >> - iommu_dma_compose_msi_msg: This function will update the MSI >> message with the IOVA when the device is behind an IOMMU. >> >> Signed-off-by: Julien Grall <julien.grall@arm.com> >> --- >> drivers/iommu/dma-iommu.c | 43 ++++++++++++++++++++++++++++++++----------- >> include/linux/dma-iommu.h | 21 +++++++++++++++++++++ >> 2 files changed, 53 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >> index 77aabe637a60..f5c1f1685095 100644 >> --- a/drivers/iommu/dma-iommu.c >> +++ b/drivers/iommu/dma-iommu.c >> @@ -888,17 +888,17 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev, >> return NULL; >> } >> >> -void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg) >> +int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr) > > I quite like the idea of moving from having an irq to having an msi_desc > passed to the IOMMU layer... > >> { >> - struct device *dev = msi_desc_to_dev(irq_get_msi_desc(irq)); >> + struct device *dev = msi_desc_to_dev(desc); >> struct iommu_domain *domain = iommu_get_domain_for_dev(dev); >> struct iommu_dma_cookie *cookie; >> - struct iommu_dma_msi_page *msi_page; >> - phys_addr_t msi_addr = (u64)msg->address_hi << 32 | msg->address_lo; >> unsigned long flags; >> >> - if (!domain || !domain->iova_cookie) >> - return; >> + if (!domain || !domain->iova_cookie) { >> + desc->iommu_cookie = NULL; >> + return 0; >> + } >> >> cookie = domain->iova_cookie; >> >> @@ -908,10 +908,33 @@ void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg) >> * of an MSI from within an IPI handler. >> */ >> spin_lock_irqsave(&cookie->msi_lock, flags); >> - msi_page = iommu_dma_get_msi_page(dev, msi_addr, domain); >> + desc->iommu_cookie = iommu_dma_get_msi_page(dev, msi_addr, domain); >> spin_unlock_irqrestore(&cookie->msi_lock, flags); >> >> - if (WARN_ON(!msi_page)) { >> + return (desc->iommu_cookie) ? 0 : -ENOMEM; >> +} >> + >> +void iommu_dma_compose_msi_msg(int irq, struct msi_msg *msg) > > ... but I'd like it even better if it was uniform. Can you please move > the irq_get_msi_desc() to the callers of iommu_dma_compose_msi_msg(), > and make both functions take a msi_desc?
Make sense. I will modify iommu_dma_compose_msi_msg to take a msi_desc in parameter.
Cheers,
-- Julien Grall
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