diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2017-06-27 18:16:47 +0200 |
|---|---|---|
| committer | Joerg Roedel <jroedel@suse.de> | 2017-06-28 12:23:01 +0200 |
| commit | aaffaa8a3b5950c47e5f7573c34bc47de8894a18 (patch) | |
| tree | efe486589baa4710920092a76c01c97f31ed247b /drivers/iommu | |
| parent | c0bc126f97fb929b3ae02c1c62322645d70eb408 (diff) | |
iommu/iova: Don't disable preempt around this_cpu_ptr()
Commit 583248e6620a ("iommu/iova: Disable preemption around use of
this_cpu_ptr()") disables preemption while accessing a per-CPU variable.
This does keep lockdep quiet. However I don't see the point why it is
bad if we get migrated after its access to another CPU.
__iova_rcache_insert() and __iova_rcache_get() immediately locks the
variable after obtaining it - before accessing its members.
_If_ we get migrated away after retrieving the address of cpu_rcache
before taking the lock then the *other* task on the same CPU will
retrieve the same address of cpu_rcache and will spin on the lock.
alloc_iova_fast() disables preemption while invoking
free_cpu_cached_iovas() on each CPU. The function itself uses
per_cpu_ptr() which does not trigger a warning (like this_cpu_ptr()
does). It _could_ make sense to use get_online_cpus() instead but the we
have a hotplug notifier for CPU down (and none for up) so we are good.
Cc: Joerg Roedel <joro@8bytes.org>
Cc: iommu@lists.linux-foundation.org
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Diffstat (limited to 'drivers/iommu')
| -rw-r--r-- | drivers/iommu/iova.c | 9 |
1 files changed, 3 insertions, 6 deletions
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index 5c88ba70e4e0..f0ff0aa04081 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -22,6 +22,7 @@ #include <linux/slab.h> #include <linux/smp.h> #include <linux/bitops.h> +#include <linux/cpu.h> static bool iova_rcache_insert(struct iova_domain *iovad, unsigned long pfn, @@ -398,10 +399,8 @@ retry: /* Try replenishing IOVAs by flushing rcache. */ flushed_rcache = true; - preempt_disable(); for_each_online_cpu(cpu) free_cpu_cached_iovas(cpu, iovad); - preempt_enable(); goto retry; } @@ -729,7 +728,7 @@ static bool __iova_rcache_insert(struct iova_domain *iovad, bool can_insert = false; unsigned long flags; - cpu_rcache = get_cpu_ptr(rcache->cpu_rcaches); + cpu_rcache = raw_cpu_ptr(rcache->cpu_rcaches); spin_lock_irqsave(&cpu_rcache->lock, flags); if (!iova_magazine_full(cpu_rcache->loaded)) { @@ -759,7 +758,6 @@ static bool __iova_rcache_insert(struct iova_domain *iovad, iova_magazine_push(cpu_rcache->loaded, iova_pfn); spin_unlock_irqrestore(&cpu_rcache->lock, flags); - put_cpu_ptr(rcache->cpu_rcaches); if (mag_to_free) { iova_magazine_free_pfns(mag_to_free, iovad); @@ -793,7 +791,7 @@ static unsigned long __iova_rcache_get(struct iova_rcache *rcache, bool has_pfn = false; unsigned long flags; - cpu_rcache = get_cpu_ptr(rcache->cpu_rcaches); + cpu_rcache = raw_cpu_ptr(rcache->cpu_rcaches); spin_lock_irqsave(&cpu_rcache->lock, flags); if (!iova_magazine_empty(cpu_rcache->loaded)) { @@ -815,7 +813,6 @@ static unsigned long __iova_rcache_get(struct iova_rcache *rcache, iova_pfn = iova_magazine_pop(cpu_rcache->loaded, limit_pfn); spin_unlock_irqrestore(&cpu_rcache->lock, flags); - put_cpu_ptr(rcache->cpu_rcaches); return iova_pfn; } |