lkml.org 
[lkml]   [2019]   [Apr]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 6/9] iommu/amd: Implement map_atomic
Date
Instead of using a spin lock I removed the mutex lock from both the
amd_iommu_map and amd_iommu_unmap path as well. iommu_map doesn’t lock
while mapping and so if iommu_map is called by two different threads on
the same iova region it results in a race condition even with the locks.
So the locking in amd_iommu_map and amd_iommu_unmap doesn't add any real
protection. The solution to this is for whatever manages the allocated
iova’s externally to make sure iommu_map isn’t called twice on the same
region at the same time.

Signed-off-by: Tom Murphy <tmurphy@arista.com>
---
drivers/iommu/amd_iommu.c | 25 ++++++++++++++++++-------
1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 2d4ee10626b4..b45e0e033adc 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -3089,12 +3089,12 @@ static int amd_iommu_attach_device(struct iommu_domain *dom,
return ret;
}

-static int amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
- phys_addr_t paddr, size_t page_size, int iommu_prot)
+static int __amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
+ phys_addr_t paddr, size_t page_size, int iommu_prot,
+ gfp_t gfp)
{
struct protection_domain *domain = to_pdomain(dom);
int prot = 0;
- int ret;

if (domain->mode == PAGE_MODE_NONE)
return -EINVAL;
@@ -3104,11 +3104,21 @@ static int amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
if (iommu_prot & IOMMU_WRITE)
prot |= IOMMU_PROT_IW;

- mutex_lock(&domain->api_lock);
- ret = iommu_map_page(domain, iova, paddr, page_size, prot, GFP_KERNEL);
- mutex_unlock(&domain->api_lock);
+ return iommu_map_page(domain, iova, paddr, page_size, prot, gfp);
+}

- return ret;
+static int amd_iommu_map(struct iommu_domain *dom, unsigned long iova,
+ phys_addr_t paddr, size_t page_size, int iommu_prot)
+{
+ return __amd_iommu_map(dom, iova, paddr, page_size, iommu_prot,
+ GFP_KERNEL);
+}
+
+static int amd_iommu_map_atomic(struct iommu_domain *dom, unsigned long iova,
+ phys_addr_t paddr, size_t page_size, int iommu_prot)
+{
+ return __amd_iommu_map(dom, iova, paddr, page_size, iommu_prot,
+ GFP_ATOMIC);
}

static size_t amd_iommu_unmap(struct iommu_domain *dom, unsigned long iova,
@@ -3262,6 +3272,7 @@ const struct iommu_ops amd_iommu_ops = {
.attach_dev = amd_iommu_attach_device,
.detach_dev = amd_iommu_detach_device,
.map = amd_iommu_map,
+ .map_atomic = amd_iommu_map_atomic,
.unmap = amd_iommu_unmap,
.iova_to_phys = amd_iommu_iova_to_phys,
.add_device = amd_iommu_add_device,
--
2.17.1
\
 
 \ /
  Last update: 2019-04-11 20:50    [W:0.213 / U:8.892 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site