[PATCH v3 05/24] vfio: powerpc/spapr: Move locked_vm accounting to helpers

[Alexey Kardashevskiy]

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. This also prints
pid of the current process in pr_warn/pr_debug.

Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
---
 drivers/vfio/vfio_iommu_spapr_tce.c | 72 +++++++++++++++++++++++++++----------
 1 file changed, 53 insertions(+), 19 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c 
b/drivers/vfio/vfio_iommu_spapr_tce.c
index c596053..29d5708 100644
--- a/drivers/vfio/vfio_iommu_spapr_tce.c
+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
@@ -29,6 +29,47 @@
 static void tce_iommu_detach_group(void *iommu_data,
                struct iommu_group *iommu_group);
 
+#define IOMMU_TABLE_PAGES(tbl) \
+               (((tbl)->it_size << (tbl)->it_page_shift) >> PAGE_SHIFT)
+
+static long try_increment_locked_vm(long npages)
+{
+       long ret = 0, locked, lock_limit;
+
+       if (!current || !current->mm)
+               return -ESRCH; /* process exited */
+
+       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("[%d] RLIMIT_MEMLOCK (%ld) exceeded\n",
+                               current->pid, rlimit(RLIMIT_MEMLOCK));
+               ret = -ENOMEM;
+       } else {
+               current->mm->locked_vm += npages;
+       }
+       pr_debug("[%d] RLIMIT_MEMLOCK+ %ld pages\n", current->pid,
+                       current->mm->locked_vm);
+       up_write(&current->mm->mmap_sem);
+
+       return ret;
+}
+
+static void decrement_locked_vm(long npages)
+{
+       if (!current || !current->mm)
+               return; /* process exited */
+
+       down_write(&current->mm->mmap_sem);
+       if (npages > current->mm->locked_vm)
+               npages = current->mm->locked_vm;
+       current->mm->locked_vm -= npages;
+       pr_debug("[%d] RLIMIT_MEMLOCK- %ld pages\n", current->pid,
+                       current->mm->locked_vm);
+       up_write(&current->mm->mmap_sem);
+}
+
 /*
  * VFIO IOMMU fd for SPAPR_TCE IOMMU implementation
  *
@@ -66,8 +107,6 @@ static bool tce_check_page_size(struct page *page, unsigned 
page_shift)
 static int tce_iommu_enable(struct tce_container *container)
 {
        int ret = 0;
-       unsigned long locked, lock_limit, npages;
-       struct iommu_table *tbl = container->tbl;
 
        if (!container->tbl)
                return -ENXIO;
@@ -95,21 +134,19 @@ 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.
         */
-       down_write(&current->mm->mmap_sem);
-       npages = (tbl->it_size << tbl->it_page_shift) >> 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 {
+       ret = try_increment_locked_vm(IOMMU_TABLE_PAGES(container->tbl));
+       if (ret)
+               return ret;
 
-               current->mm->locked_vm += npages;
-               container->enabled = true;
-       }
-       up_write(&current->mm->mmap_sem);
+       container->enabled = true;
 
        return ret;
 }
@@ -124,10 +161,7 @@ static void tce_iommu_disable(struct tce_container 
*container)
        if (!container->tbl || !current->mm)
                return;
 
-       down_write(&current->mm->mmap_sem);
-       current->mm->locked_vm -= (container->tbl->it_size <<
-                       container->tbl->it_page_shift) >> PAGE_SHIFT;
-       up_write(&current->mm->mmap_sem);
+       decrement_locked_vm(IOMMU_TABLE_PAGES(container->tbl));
 }
 
 static void *tce_iommu_open(unsigned long arg)
-- 
2.0.0

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