From: Robin Murphy <robin.murphy@arm.com>
To: Lu Baolu <baolu.lu@linux.intel.com>, iommu@lists.linux.dev
Cc: Joerg Roedel <joro@8bytes.org>, Jason Gunthorpe <jgg@nvidia.com>,
Christoph Hellwig <hch@infradead.org>,
Kevin Tian <kevin.tian@intel.com>, Will Deacon <will@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/6] ARM/dma-mapping: Add arm_iommu_release_device()
Date: Fri, 10 Mar 2023 22:04:18 +0000 [thread overview]
Message-ID: <7b248ba1-3967-5cd8-82e9-0268c706d320@arm.com> (raw)
In-Reply-To: <20230306025804.13912-2-baolu.lu@linux.intel.com>
On 2023-03-06 02:57, Lu Baolu wrote:
> It is like arm_iommu_detach_device() except it handles the special case
> of being called under an iommu driver's release operation. In this case
> the driver must have already detached the device from any attached
> domain before calling this function.
>
> Replace arm_iommu_detach_device() with arm_iommu_release_device() in the
> release path of the ipmmu-vmsa driver.
>
> The bonus is that it also removes a obstacle of arm_iommu_detach_device()
> re-entering the iommu core during release_device. With this removed, the
> iommu core code could be simplified a lot.
>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> arch/arm/include/asm/dma-iommu.h | 1 +
> arch/arm/mm/dma-mapping.c | 25 +++++++++++++++++++++++++
> drivers/iommu/ipmmu-vmsa.c | 15 +++++++++++++--
> 3 files changed, 39 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/include/asm/dma-iommu.h b/arch/arm/include/asm/dma-iommu.h
> index fe9ef6f79e9c..ea7198a17861 100644
> --- a/arch/arm/include/asm/dma-iommu.h
> +++ b/arch/arm/include/asm/dma-iommu.h
> @@ -31,6 +31,7 @@ void arm_iommu_release_mapping(struct dma_iommu_mapping *mapping);
> int arm_iommu_attach_device(struct device *dev,
> struct dma_iommu_mapping *mapping);
> void arm_iommu_detach_device(struct device *dev);
> +void arm_iommu_release_device(struct device *dev);
>
> #endif /* __KERNEL__ */
> #endif
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 8bc01071474a..96fa27f4a164 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1682,6 +1682,31 @@ int arm_iommu_attach_device(struct device *dev,
> }
> EXPORT_SYMBOL_GPL(arm_iommu_attach_device);
>
> +/**
> + * arm_iommu_release_device
> + * @dev: valid struct device pointer
> + *
> + * This is like arm_iommu_detach_device() except it handles the special
> + * case of being called under an iommu driver's release operation. In this
> + * case the driver must have already detached the device from any attached
> + * domain before calling this function.
> + */
> +void arm_iommu_release_device(struct device *dev)
> +{
> + struct dma_iommu_mapping *mapping;
> +
> + mapping = to_dma_iommu_mapping(dev);
> + if (!mapping) {
> + dev_warn(dev, "Not attached\n");
> + return;
> + }
> +
> + kref_put(&mapping->kref, release_iommu_mapping);
> + to_dma_iommu_mapping(dev) = NULL;
> + set_dma_ops(dev, NULL);
> +}
> +EXPORT_SYMBOL_GPL(arm_iommu_release_device);
> +
> /**
> * arm_iommu_detach_device
> * @dev: valid struct device pointer
> diff --git a/drivers/iommu/ipmmu-vmsa.c b/drivers/iommu/ipmmu-vmsa.c
> index bdf1a4e5eae0..de9c74cf61a4 100644
> --- a/drivers/iommu/ipmmu-vmsa.c
> +++ b/drivers/iommu/ipmmu-vmsa.c
> @@ -30,7 +30,7 @@
> #define arm_iommu_create_mapping(...) NULL
> #define arm_iommu_attach_device(...) -ENODEV
> #define arm_iommu_release_mapping(...) do {} while (0)
> -#define arm_iommu_detach_device(...) do {} while (0)
> +#define arm_iommu_release_device(...) do {} while (0)
> #endif
>
> #define IPMMU_CTX_MAX 16U
> @@ -820,7 +820,18 @@ static void ipmmu_probe_finalize(struct device *dev)
>
> static void ipmmu_release_device(struct device *dev)
> {
> - arm_iommu_detach_device(dev);
> + struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
> + struct ipmmu_vmsa_device *mmu = to_ipmmu(dev);
> + unsigned int i;
> +
> + for (i = 0; i < fwspec->num_ids; ++i) {
> + unsigned int utlb = fwspec->ids[i];
> +
> + ipmmu_imuctr_write(mmu, utlb, 0);
> + mmu->utlb_ctx[utlb] = IPMMU_CTX_INVALID;
> + }
> +
> + arm_iommu_release_device(dev);
Just call the existing arm_iommu_release_mapping(). Look at where the
BUS_NOTIFY_REMOVED_DEVICE point is in device_del(); this device is not
coming back. Zeroing out pointers and testing for a condition which
cannot be true by construction is simply a waste of time and code.
Thanks,
Robin.
> }
>
> static struct iommu_group *ipmmu_find_group(struct device *dev)
next prev parent reply other threads:[~2023-03-10 22:04 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-06 2:57 [PATCH v3 0/6] iommu: Extend changing default domain to normal group Lu Baolu
2023-03-06 2:57 ` [PATCH v3 1/6] ARM/dma-mapping: Add arm_iommu_release_device() Lu Baolu
2023-03-10 1:00 ` Jason Gunthorpe
2023-03-10 22:04 ` Robin Murphy [this message]
2023-03-12 3:53 ` Baolu Lu
2023-03-06 2:58 ` [PATCH v3 2/6] iommu: Split iommu_group_remove_device() into helpers Lu Baolu
2023-03-10 1:01 ` Jason Gunthorpe
2023-03-06 2:58 ` [PATCH v3 3/6] iommu: Same critical region for device release and removal Lu Baolu
2023-03-10 1:08 ` Jason Gunthorpe
2023-03-06 2:58 ` [PATCH v3 4/6] iommu: Move lock from iommu_change_dev_def_domain() to its caller Lu Baolu
2023-03-10 1:16 ` Jason Gunthorpe
2023-03-06 2:58 ` [PATCH v3 5/6] iommu: Replace device_lock() with group->mutex Lu Baolu
2023-03-10 1:30 ` Jason Gunthorpe
2023-03-06 2:58 ` [PATCH v3 6/6] iommu: Cleanup iommu_change_dev_def_domain() Lu Baolu
2023-03-10 1:30 ` Jason Gunthorpe
2023-03-10 1:32 ` [PATCH v3 0/6] iommu: Extend changing default domain to normal group Jason Gunthorpe
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