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iommu/dma: Relax locking in iommu_dma_prepare_msi() 

[ Upstream commit c18647900e ]

Since commit ece6e6f021 ("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: Qian Cai <cai@lca.pw>
Tested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
5.4-rM2-2.2.x-imx-squashed
Robin Murphy 2019-12-09 19:47:25 +00:00 committed by Greg Kroah-Hartman
parent 88184162e9
commit 2d26e06cb1
1 changed files with 8 additions and 9 deletions
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17
drivers/iommu/dma-iommu.c
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@ -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>
@ -43,7 +44,6 @@ 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;
@ -62,7 +62,6 @@ 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;
}
@ -1150,7 +1149,7 @@ 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;
@ -1180,7 +1179,7 @@ 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;
@ -1190,13 +1189,13 @@ 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);