[PATCH 11/13] vfio: powerpc/spapr: Move locked_vm accounting to helpers

From: Alexey Kardashevskiy
Date: Fri Aug 29 2014 - 03:59:41 EST


There moves locked pages accounting to helpers.
Later they will be reused for Dynamic DMA windows (DDW).

While we are here, update the comment explaining why RLIMIT_MEMLOCK
might be required to be bigger than the guest RAM.

Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
---
drivers/vfio/vfio_iommu_spapr_tce.c | 71 +++++++++++++++++++++++++++----------
1 file changed, 53 insertions(+), 18 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
index 1c1a9c4..c9fac97 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -29,6 +29,46 @@
static void tce_iommu_detach_group(void *iommu_data,
struct iommu_group *iommu_group);

+static long try_increment_locked_vm(struct iommu_table *tbl)
+{
+ long ret = 0, locked, lock_limit, npages;
+
+ if (!current || !current->mm)
+ return -ESRCH; /* process exited */
+
+ npages = (tbl->it_size << IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
+
+ down_write(&current->mm->mmap_sem);
+ locked = current->mm->locked_vm + npages;
+ lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+ if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
+ pr_warn("RLIMIT_MEMLOCK (%ld) exceeded\n",
+ rlimit(RLIMIT_MEMLOCK));
+ ret = -ENOMEM;
+ } else {
+ current->mm->locked_vm += npages;
+ }
+ up_write(&current->mm->mmap_sem);
+
+ return ret;
+}
+
+static void decrement_locked_vm(struct iommu_table *tbl)
+{
+ long npages;
+
+ if (!current || !current->mm)
+ return; /* process exited */
+
+ npages = (tbl->it_size << IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
+
+ down_write(&current->mm->mmap_sem);
+ if (npages > current->mm->locked_vm)
+ npages = current->mm->locked_vm;
+ current->mm->locked_vm -= npages;
+ up_write(&current->mm->mmap_sem);
+}
+
/*
* VFIO IOMMU fd for SPAPR_TCE IOMMU implementation
*
@@ -86,7 +126,6 @@ static void tce_iommu_take_ownership_notify(struct spapr_tce_iommu_group *data,
static int tce_iommu_enable(struct tce_container *container)
{
int ret = 0;
- unsigned long locked, lock_limit, npages;
struct iommu_table *tbl;
struct spapr_tce_iommu_group *data;

@@ -120,24 +159,23 @@ static int tce_iommu_enable(struct tce_container *container)
* Also we don't have a nice way to fail on H_PUT_TCE due to ulimits,
* that would effectively kill the guest at random points, much better
* enforcing the limit based on the max that the guest can map.
+ *
+ * Unfortunately at the moment it counts whole tables, no matter how
+ * much memory the guest has. I.e. for 4GB guest and 4 IOMMU groups
+ * each with 2GB DMA window, 8GB will be counted here. The reason for
+ * this is that we cannot tell here the amount of RAM used by the guest
+ * as this information is only available from KVM and VFIO is
+ * KVM agnostic.
*/
tbl = data->ops->get_table(data, 0);
if (!tbl)
return -ENXIO;

- down_write(&current->mm->mmap_sem);
- npages = (tbl->it_size << IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
- locked = current->mm->locked_vm + npages;
- lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
- if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
- pr_warn("RLIMIT_MEMLOCK (%ld) exceeded\n",
- rlimit(RLIMIT_MEMLOCK));
- ret = -ENOMEM;
- } else {
- current->mm->locked_vm += npages;
- container->enabled = true;
- }
- up_write(&current->mm->mmap_sem);
+ ret = try_increment_locked_vm(tbl);
+ if (ret)
+ return ret;
+
+ container->enabled = true;

return ret;
}
@@ -163,10 +201,7 @@ static void tce_iommu_disable(struct tce_container *container)
if (!tbl)
return;

- down_write(&current->mm->mmap_sem);
- current->mm->locked_vm -= (tbl->it_size <<
- IOMMU_PAGE_SHIFT_4K) >> PAGE_SHIFT;
- up_write(&current->mm->mmap_sem);
+ decrement_locked_vm(tbl);
}

static void *tce_iommu_open(unsigned long arg)
--
2.0.0

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/