Commit c1864790 authored by Robin Murphy's avatar Robin Murphy Committed by Joerg Roedel
Browse files

iommu/dma: Relax locking in iommu_dma_prepare_msi() 



Since commit ece6e6f0 ("iommu/dma-iommu: Split iommu_dma_map_msi_msg()
in two parts"), iommu_dma_prepare_msi() should no longer have to worry
about preempting itself, nor being called in atomic context at all. Thus
we can downgrade the IRQ-safe locking to a simple mutex to avoid angering
the new might_sleep() check in iommu_map().

Reported-by: default avatarQian Cai <cai@lca.pw>
Tested-by: default avatarJean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: default avatarRobin Murphy <robin.murphy@arm.com>
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
parent f81b846d

drivers/iommu/dma-iommu.c

+8 −9
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ 
#include <linux/iova.h>

#include <linux/irq.h>

#include <linux/mm.h>

#include <linux/mutex.h>

#include <linux/pci.h>

#include <linux/scatterlist.h>

#include <linux/vmalloc.h>
@@ -44,7 +45,6 @@ struct iommu_dma_cookie { 
		dma_addr_t		msi_iova;

	};

	struct list_head		msi_page_list;

	spinlock_t			msi_lock;



	/* Domain for flush queue callback; NULL if flush queue not in use */

	struct iommu_domain		*fq_domain;
@@ -63,7 +63,6 @@ static struct iommu_dma_cookie *cookie_alloc(enum iommu_dma_cookie_type type) 


	cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);

	if (cookie) {

		spin_lock_init(&cookie->msi_lock);

		INIT_LIST_HEAD(&cookie->msi_page_list);

		cookie->type = type;

	}
@@ -1176,7 +1175,7 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev, 
		if (msi_page->phys == msi_addr)

			return msi_page;



	msi_page = kzalloc(sizeof(*msi_page), GFP_ATOMIC);

	msi_page = kzalloc(sizeof(*msi_page), GFP_KERNEL);

	if (!msi_page)

		return NULL;
@@ -1206,7 +1205,7 @@ int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr) 
	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);

	struct iommu_dma_cookie *cookie;

	struct iommu_dma_msi_page *msi_page;

	unsigned long flags;

	static DEFINE_MUTEX(msi_prepare_lock); /* see below */



	if (!domain || !domain->iova_cookie) {

		desc->iommu_cookie = NULL;
@@ -1216,13 +1215,13 @@ int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr) 
	cookie = domain->iova_cookie;



	/*

	 * We disable IRQs to rule out a possible inversion against

	 * irq_desc_lock if, say, someone tries to retarget the affinity

	 * of an MSI from within an IPI handler.

	 * In fact the whole prepare operation should already be serialised by

	 * irq_domain_mutex further up the callchain, but that's pretty subtle

	 * on its own, so consider this locking as failsafe documentation...

	 */

	spin_lock_irqsave(&cookie->msi_lock, flags);

	mutex_lock(&msi_prepare_lock);

	msi_page = iommu_dma_get_msi_page(dev, msi_addr, domain);

	spin_unlock_irqrestore(&cookie->msi_lock, flags);

	mutex_unlock(&msi_prepare_lock);



	msi_desc_set_iommu_cookie(desc, msi_page);

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