blob: fef4c2f5da42fd7bb315c84374f326df07875c2b [file] [log] [blame]
From 984c5785df3af8bfe7c9ebb730202c86cccf38d2 Mon Sep 17 00:00:00 2001
From: Robin Murphy <robin.murphy@arm.com>
Date: Mon, 9 Dec 2019 19:47:25 +0000
Subject: [PATCH] iommu/dma: Relax locking in iommu_dma_prepare_msi()
commit c18647900ec864d401ba09b3bbd5b34f331f8d26 upstream.
Since commit ece6e6f0218b ("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: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 8c02d2283d64..f77f201b7a8b 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -17,6 +17,7 @@
#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>
@@ -41,7 +42,6 @@ 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;
@@ -60,7 +60,6 @@ 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;
}
@@ -877,7 +876,7 @@ 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;
@@ -902,7 +901,7 @@ 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;
@@ -912,13 +911,13 @@ 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);
--
2.7.4