linux-kernel - [PATCH 11/13] vfio: powerpc/spapr: Move locked

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Message-Id: <1409299156-618-12-git-send-email-aik@ozlabs.ru>
Date:	Fri, 29 Aug 2014 17:59:14 +1000
From:	Alexey Kardashevskiy <aik@...abs.ru>
To:	linuxppc-dev@...ts.ozlabs.org
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Alex Williamson <alex.williamson@...hat.com>,
	Gavin Shan <gwshan@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, cbe-oss-dev@...ts.ozlabs.org,
	kvm@...r.kernel.org, linux-api@...r.kernel.org
Subject: [PATCH 11/13] vfio: powerpc/spapr: Move locked_vm accounting to helpers

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@...abs.ru>
---
 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

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