* [PATCH 0/2] use vfio_iova_rw() to read/write IOVAs from CPU side
@ 2020-01-03 1:00 Yan Zhao
2020-01-03 1:02 ` [PATCH 1/2] vfio: introduce vfio_iova_rw to read/write a range of IOVAs Yan Zhao
2020-01-03 1:03 ` [PATCH 2/2] drm/i915/gvt: subsitute kvm_read/write_guest with vfio_iova_rw Yan Zhao
0 siblings, 2 replies; 6+ messages in thread
From: Yan Zhao @ 2020-01-03 1:00 UTC (permalink / raw)
To: alex.williamson, zhenyuw
Cc: kvm, linux-kernel, intel-gvt, pbonzini, kevin.tian, Yan Zhao
When device models read/write memory pointed by a range of IOVAs, it is
better to use vfio interfaces. And because this read/write is from CPUs,
there's no need to call vfio_pin_pages() to pin those memory.
patch 1 introduces interface vfio_iova_rw() in vfio to read/write
userspace IOVAs without pinning userspace pages.
patch 2 let gvt switch from kvm side rw interface to vfio_iova_rw().
Yan Zhao (2):
vfio: introduce vfio_iova_rw to read/write a range of IOVAs
drm/i915/gvt: subsitute kvm_read/write_guest with vfio_iova_rw
drivers/gpu/drm/i915/gvt/kvmgt.c | 26 +++-------
drivers/vfio/vfio.c | 45 ++++++++++++++++++
drivers/vfio/vfio_iommu_type1.c | 81 ++++++++++++++++++++++++++++++++
include/linux/vfio.h | 5 ++
4 files changed, 138 insertions(+), 19 deletions(-)
--
2.17.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 1/2] vfio: introduce vfio_iova_rw to read/write a range of IOVAs
2020-01-03 1:00 [PATCH 0/2] use vfio_iova_rw() to read/write IOVAs from CPU side Yan Zhao
@ 2020-01-03 1:02 ` Yan Zhao
2020-01-09 18:16 ` Alex Williamson
2020-01-03 1:03 ` [PATCH 2/2] drm/i915/gvt: subsitute kvm_read/write_guest with vfio_iova_rw Yan Zhao
1 sibling, 1 reply; 6+ messages in thread
From: Yan Zhao @ 2020-01-03 1:02 UTC (permalink / raw)
To: alex.williamson
Cc: zhenyuw, kvm, linux-kernel, intel-gvt, pbonzini, kevin.tian, Yan Zhao
vfio_iova_rw will read/write a range of userspace memory (starting form
device iova to iova + len -1) into a kenrel buffer without pinning the
userspace memory.
TODO: vfio needs to mark the iova dirty if vfio_iova_rw(write) is
called.
Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
---
drivers/vfio/vfio.c | 45 ++++++++++++++++++
drivers/vfio/vfio_iommu_type1.c | 81 +++++++++++++++++++++++++++++++++
include/linux/vfio.h | 5 ++
3 files changed, 131 insertions(+)
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index c8482624ca34..36e91e647ed5 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1961,6 +1961,51 @@ int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, int npage)
}
EXPORT_SYMBOL(vfio_unpin_pages);
+/*
+ * Read/Write a range of userspace IOVAs for a device into/from a kernel
+ * buffer without pinning the userspace memory
+ * @dev [in] : device
+ * @iova [in] : base IOVA of a userspace buffer
+ * @data [in] : pointer to kernel buffer
+ * @len [in] : kernel buffer length
+ * @write : indicate read or write
+ * Return error on failure or 0 on success.
+ */
+int vfio_iova_rw(struct device *dev, unsigned long iova, void *data,
+ unsigned long len, bool write)
+{
+ struct vfio_container *container;
+ struct vfio_group *group;
+ struct vfio_iommu_driver *driver;
+ int ret = 0;
+
+ if (!dev || !data || len <= 0)
+ return -EINVAL;
+
+ group = vfio_group_get_from_dev(dev);
+ if (!group)
+ return -ENODEV;
+
+ ret = vfio_group_add_container_user(group);
+ if (ret)
+ goto out;
+
+ container = group->container;
+ driver = container->iommu_driver;
+
+ if (likely(driver && driver->ops->iova_rw))
+ ret = driver->ops->iova_rw(container->iommu_data,
+ iova, data, len, write);
+ else
+ ret = -ENOTTY;
+
+ vfio_group_try_dissolve_container(group);
+out:
+ vfio_group_put(group);
+ return ret;
+}
+EXPORT_SYMBOL(vfio_iova_rw);
+
static int vfio_register_iommu_notifier(struct vfio_group *group,
unsigned long *events,
struct notifier_block *nb)
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 2ada8e6cdb88..aee191077235 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -27,6 +27,7 @@
#include <linux/iommu.h>
#include <linux/module.h>
#include <linux/mm.h>
+#include <linux/mmu_context.h>
#include <linux/rbtree.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
@@ -2326,6 +2327,85 @@ static int vfio_iommu_type1_unregister_notifier(void *iommu_data,
return blocking_notifier_chain_unregister(&iommu->notifier, nb);
}
+static int next_segment(unsigned long len, int offset)
+{
+ if (len > PAGE_SIZE - offset)
+ return PAGE_SIZE - offset;
+ else
+ return len;
+}
+
+static int vfio_iommu_type1_rw_iova_seg(struct vfio_iommu *iommu,
+ unsigned long iova, void *data,
+ unsigned long seg_len,
+ unsigned long offset,
+ bool write)
+{
+ struct mm_struct *mm;
+ unsigned long vaddr;
+ struct vfio_dma *dma;
+ bool kthread = current->mm == NULL;
+ int ret = 0;
+
+ dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
+ if (!dma)
+ return -EINVAL;
+
+ mm = get_task_mm(dma->task);
+
+ if (!mm)
+ return -ENODEV;
+
+ if (kthread)
+ use_mm(mm);
+ else if (current->mm != mm) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ vaddr = dma->vaddr + iova - dma->iova + offset;
+
+ ret = write ? __copy_to_user((void __user *)vaddr,
+ data, seg_len) :
+ __copy_from_user(data, (void __user *)vaddr,
+ seg_len);
+ if (ret)
+ ret = -EFAULT;
+
+ if (kthread)
+ unuse_mm(mm);
+out:
+ mmput(mm);
+ return ret;
+}
+
+static int vfio_iommu_type1_iova_rw(void *iommu_data, unsigned long iova,
+ void *data, unsigned long len, bool write)
+{
+ struct vfio_iommu *iommu = iommu_data;
+ int offset = iova & ~PAGE_MASK;
+ int seg_len;
+ int ret = 0;
+
+ iova = iova & PAGE_MASK;
+
+ mutex_lock(&iommu->lock);
+ while ((seg_len = next_segment(len, offset)) > 0) {
+ ret = vfio_iommu_type1_rw_iova_seg(iommu, iova, data,
+ seg_len, offset, write);
+ if (ret)
+ break;
+
+ offset = 0;
+ len -= seg_len;
+ data += seg_len;
+ iova += PAGE_SIZE;
+ }
+
+ mutex_unlock(&iommu->lock);
+ return ret;
+}
+
static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
.name = "vfio-iommu-type1",
.owner = THIS_MODULE,
@@ -2338,6 +2418,7 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
.unpin_pages = vfio_iommu_type1_unpin_pages,
.register_notifier = vfio_iommu_type1_register_notifier,
.unregister_notifier = vfio_iommu_type1_unregister_notifier,
+ .iova_rw = vfio_iommu_type1_iova_rw,
};
static int __init vfio_iommu_type1_init(void)
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index e42a711a2800..7bf18a31bbcf 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -82,6 +82,8 @@ struct vfio_iommu_driver_ops {
struct notifier_block *nb);
int (*unregister_notifier)(void *iommu_data,
struct notifier_block *nb);
+ int (*iova_rw)(void *iommu_data, unsigned long iova,
+ void *data, unsigned long len, bool write);
};
extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
@@ -107,6 +109,9 @@ extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn,
extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
int npage);
+extern int vfio_iova_rw(struct device *dev, unsigned long iova, void *data,
+ unsigned long len, bool write);
+
/* each type has independent events */
enum vfio_notify_type {
VFIO_IOMMU_NOTIFY = 0,
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/2] drm/i915/gvt: subsitute kvm_read/write_guest with vfio_iova_rw
2020-01-03 1:00 [PATCH 0/2] use vfio_iova_rw() to read/write IOVAs from CPU side Yan Zhao
2020-01-03 1:02 ` [PATCH 1/2] vfio: introduce vfio_iova_rw to read/write a range of IOVAs Yan Zhao
@ 2020-01-03 1:03 ` Yan Zhao
2020-01-07 10:21 ` Paolo Bonzini
1 sibling, 1 reply; 6+ messages in thread
From: Yan Zhao @ 2020-01-03 1:03 UTC (permalink / raw)
To: zhenyuw
Cc: alex.williamson, kvm, linux-kernel, intel-gvt, pbonzini,
kevin.tian, Yan Zhao
As a device model, it is better to read/write guest memory using vfio
interface, so that vfio is able to maintain dirty info of device IOVAs.
Compared to CPU side interfaces kvm_read/write_guest(), vfio_iova_rw()
has ~600 cycles more overhead on average.
-------------------------------------
| interface | avg cpu cycles |
|-----------------------------------|
| kvm_write_guest | 1546 |
| ----------------------------------|
| kvm_read_guest | 686 |
|-----------------------------------|
| vfio_iova_rw(w) | 2233 |
|-----------------------------------|
| vfio_iova_rw(r) | 1262 |
-------------------------------------
Comparison of benchmarks scores are as blow:
---------------------------------------------------------
| avg score | kvm_read/write_guest | vfio_iova_rw |
---------------------------------------------------------
| Glmark2 | 1132 | 1138.2 |
---------------------------------------------------------
| Lightsmark | 61.558 | 61.538 |
|--------------------------------------------------------
| OpenArena | 142.77 | 136.6 |
---------------------------------------------------------
| Heaven | 698 | 686.8 |
--------------------------------------------------------
No obvious performance downgrade found.
Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
---
drivers/gpu/drm/i915/gvt/kvmgt.c | 26 +++++++-------------------
1 file changed, 7 insertions(+), 19 deletions(-)
diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c
index bd79a9718cc7..576b05db3998 100644
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1966,31 +1966,19 @@ static int kvmgt_rw_gpa(unsigned long handle, unsigned long gpa,
void *buf, unsigned long len, bool write)
{
struct kvmgt_guest_info *info;
- struct kvm *kvm;
- int idx, ret;
- bool kthread = current->mm == NULL;
+ int ret;
+ struct intel_vgpu *vgpu;
+ struct device *dev;
if (!handle_valid(handle))
return -ESRCH;
info = (struct kvmgt_guest_info *)handle;
- kvm = info->kvm;
-
- if (kthread) {
- if (!mmget_not_zero(kvm->mm))
- return -EFAULT;
- use_mm(kvm->mm);
- }
-
- idx = srcu_read_lock(&kvm->srcu);
- ret = write ? kvm_write_guest(kvm, gpa, buf, len) :
- kvm_read_guest(kvm, gpa, buf, len);
- srcu_read_unlock(&kvm->srcu, idx);
+ vgpu = info->vgpu;
+ dev = mdev_dev(vgpu->vdev.mdev);
- if (kthread) {
- unuse_mm(kvm->mm);
- mmput(kvm->mm);
- }
+ ret = write ? vfio_iova_rw(dev, gpa, buf, len, true) :
+ vfio_iova_rw(dev, gpa, buf, len, false);
return ret;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 2/2] drm/i915/gvt: subsitute kvm_read/write_guest with vfio_iova_rw
2020-01-03 1:03 ` [PATCH 2/2] drm/i915/gvt: subsitute kvm_read/write_guest with vfio_iova_rw Yan Zhao
@ 2020-01-07 10:21 ` Paolo Bonzini
0 siblings, 0 replies; 6+ messages in thread
From: Paolo Bonzini @ 2020-01-07 10:21 UTC (permalink / raw)
To: Yan Zhao, zhenyuw
Cc: alex.williamson, kvm, linux-kernel, intel-gvt, kevin.tian
On 03/01/20 02:03, Yan Zhao wrote:
> + ret = write ? vfio_iova_rw(dev, gpa, buf, len, true) :
> + vfio_iova_rw(dev, gpa, buf, len, false);
>
> return ret;
"Write" can be just the final argument to vfio_iova_rw, that is
return vfio_iova_rw(dev, gpa, buf, len, write):
Thanks,
Paolo
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] vfio: introduce vfio_iova_rw to read/write a range of IOVAs
2020-01-03 1:02 ` [PATCH 1/2] vfio: introduce vfio_iova_rw to read/write a range of IOVAs Yan Zhao
@ 2020-01-09 18:16 ` Alex Williamson
2020-01-10 3:24 ` Yan Zhao
0 siblings, 1 reply; 6+ messages in thread
From: Alex Williamson @ 2020-01-09 18:16 UTC (permalink / raw)
To: Yan Zhao; +Cc: zhenyuw, kvm, linux-kernel, pbonzini, kevin.tian
On Thu, 2 Jan 2020 20:02:17 -0500
Yan Zhao <yan.y.zhao@intel.com> wrote:
> vfio_iova_rw will read/write a range of userspace memory (starting form
> device iova to iova + len -1) into a kenrel buffer without pinning the
> userspace memory.
>
> TODO: vfio needs to mark the iova dirty if vfio_iova_rw(write) is
> called.
>
> Cc: Kevin Tian <kevin.tian@intel.com>
> Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
> ---
> drivers/vfio/vfio.c | 45 ++++++++++++++++++
> drivers/vfio/vfio_iommu_type1.c | 81 +++++++++++++++++++++++++++++++++
> include/linux/vfio.h | 5 ++
> 3 files changed, 131 insertions(+)
>
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index c8482624ca34..36e91e647ed5 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -1961,6 +1961,51 @@ int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, int npage)
> }
> EXPORT_SYMBOL(vfio_unpin_pages);
>
> +/*
> + * Read/Write a range of userspace IOVAs for a device into/from a kernel
> + * buffer without pinning the userspace memory
> + * @dev [in] : device
> + * @iova [in] : base IOVA of a userspace buffer
> + * @data [in] : pointer to kernel buffer
> + * @len [in] : kernel buffer length
> + * @write : indicate read or write
> + * Return error on failure or 0 on success.
> + */
> +int vfio_iova_rw(struct device *dev, unsigned long iova, void *data,
> + unsigned long len, bool write)
Shouldn't iova be a dma_addr_t and len be a size_t? AIUI this function
performs the equivalent behavior of the device itself performing a DMA.
Hmm, should the interface be named vfio_dma_rw()?
> +{
> + struct vfio_container *container;
> + struct vfio_group *group;
> + struct vfio_iommu_driver *driver;
> + int ret = 0;
> +
> + if (!dev || !data || len <= 0)
> + return -EINVAL;
> +
> + group = vfio_group_get_from_dev(dev);
> + if (!group)
> + return -ENODEV;
> +
> + ret = vfio_group_add_container_user(group);
> + if (ret)
> + goto out;
> +
> + container = group->container;
> + driver = container->iommu_driver;
> +
> + if (likely(driver && driver->ops->iova_rw))
> + ret = driver->ops->iova_rw(container->iommu_data,
> + iova, data, len, write);
> + else
> + ret = -ENOTTY;
> +
> + vfio_group_try_dissolve_container(group);
> +out:
> + vfio_group_put(group);
> + return ret;
> +}
> +EXPORT_SYMBOL(vfio_iova_rw);
> +
> static int vfio_register_iommu_notifier(struct vfio_group *group,
> unsigned long *events,
> struct notifier_block *nb)
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 2ada8e6cdb88..aee191077235 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -27,6 +27,7 @@
> #include <linux/iommu.h>
> #include <linux/module.h>
> #include <linux/mm.h>
> +#include <linux/mmu_context.h>
> #include <linux/rbtree.h>
> #include <linux/sched/signal.h>
> #include <linux/sched/mm.h>
> @@ -2326,6 +2327,85 @@ static int vfio_iommu_type1_unregister_notifier(void *iommu_data,
> return blocking_notifier_chain_unregister(&iommu->notifier, nb);
> }
>
> +static int next_segment(unsigned long len, int offset)
> +{
> + if (len > PAGE_SIZE - offset)
> + return PAGE_SIZE - offset;
> + else
> + return len;
> +}
> +
> +static int vfio_iommu_type1_rw_iova_seg(struct vfio_iommu *iommu,
> + unsigned long iova, void *data,
> + unsigned long seg_len,
> + unsigned long offset,
> + bool write)
> +{
> + struct mm_struct *mm;
> + unsigned long vaddr;
> + struct vfio_dma *dma;
> + bool kthread = current->mm == NULL;
> + int ret = 0;
> +
> + dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
> + if (!dma)
> + return -EINVAL;
> +
> + mm = get_task_mm(dma->task);
> +
> + if (!mm)
> + return -ENODEV;
> +
> + if (kthread)
> + use_mm(mm);
> + else if (current->mm != mm) {
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + vaddr = dma->vaddr + iova - dma->iova + offset;
Parenthesis here would be useful and might prevent overflow, ie:
dma->vaddr + (iova - dma->iova) + offset
> +
> + ret = write ? __copy_to_user((void __user *)vaddr,
> + data, seg_len) :
> + __copy_from_user(data, (void __user *)vaddr,
> + seg_len);
> + if (ret)
> + ret = -EFAULT;
> +
> + if (kthread)
> + unuse_mm(mm);
> +out:
> + mmput(mm);
> + return ret;
> +}
> +
> +static int vfio_iommu_type1_iova_rw(void *iommu_data, unsigned long iova,
> + void *data, unsigned long len, bool write)
> +{
> + struct vfio_iommu *iommu = iommu_data;
> + int offset = iova & ~PAGE_MASK;
> + int seg_len;
> + int ret = 0;
> +
> + iova = iova & PAGE_MASK;
> +
> + mutex_lock(&iommu->lock);
> + while ((seg_len = next_segment(len, offset)) > 0) {
> + ret = vfio_iommu_type1_rw_iova_seg(iommu, iova, data,
> + seg_len, offset, write);
Why do we need to split operations at page boundaries? It seems really
inefficient that at each page crossing we need to lookup the vfio_dma
again (probably the same one), switch to the mm (probably the same one),
and perform another copy_{to,from}_user() when potentially have
everything we need to perform a larger copy. Thanks,
Alex
> + if (ret)
> + break;
> +
> + offset = 0;
> + len -= seg_len;
> + data += seg_len;
> + iova += PAGE_SIZE;
> + }
> +
> + mutex_unlock(&iommu->lock);
> + return ret;
> +}
> +
> static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
> .name = "vfio-iommu-type1",
> .owner = THIS_MODULE,
> @@ -2338,6 +2418,7 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
> .unpin_pages = vfio_iommu_type1_unpin_pages,
> .register_notifier = vfio_iommu_type1_register_notifier,
> .unregister_notifier = vfio_iommu_type1_unregister_notifier,
> + .iova_rw = vfio_iommu_type1_iova_rw,
> };
>
> static int __init vfio_iommu_type1_init(void)
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index e42a711a2800..7bf18a31bbcf 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -82,6 +82,8 @@ struct vfio_iommu_driver_ops {
> struct notifier_block *nb);
> int (*unregister_notifier)(void *iommu_data,
> struct notifier_block *nb);
> + int (*iova_rw)(void *iommu_data, unsigned long iova,
> + void *data, unsigned long len, bool write);
> };
>
> extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
> @@ -107,6 +109,9 @@ extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn,
> extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
> int npage);
>
> +extern int vfio_iova_rw(struct device *dev, unsigned long iova, void *data,
> + unsigned long len, bool write);
> +
> /* each type has independent events */
> enum vfio_notify_type {
> VFIO_IOMMU_NOTIFY = 0,
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] vfio: introduce vfio_iova_rw to read/write a range of IOVAs
2020-01-09 18:16 ` Alex Williamson
@ 2020-01-10 3:24 ` Yan Zhao
0 siblings, 0 replies; 6+ messages in thread
From: Yan Zhao @ 2020-01-10 3:24 UTC (permalink / raw)
To: Alex Williamson; +Cc: zhenyuw, kvm, linux-kernel, pbonzini, Tian, Kevin
On Fri, Jan 10, 2020 at 02:16:36AM +0800, Alex Williamson wrote:
> On Thu, 2 Jan 2020 20:02:17 -0500
> Yan Zhao <yan.y.zhao@intel.com> wrote:
>
> > vfio_iova_rw will read/write a range of userspace memory (starting form
> > device iova to iova + len -1) into a kenrel buffer without pinning the
> > userspace memory.
> >
> > TODO: vfio needs to mark the iova dirty if vfio_iova_rw(write) is
> > called.
> >
> > Cc: Kevin Tian <kevin.tian@intel.com>
> > Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
> > ---
> > drivers/vfio/vfio.c | 45 ++++++++++++++++++
> > drivers/vfio/vfio_iommu_type1.c | 81 +++++++++++++++++++++++++++++++++
> > include/linux/vfio.h | 5 ++
> > 3 files changed, 131 insertions(+)
> >
> > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> > index c8482624ca34..36e91e647ed5 100644
> > --- a/drivers/vfio/vfio.c
> > +++ b/drivers/vfio/vfio.c
> > @@ -1961,6 +1961,51 @@ int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, int npage)
> > }
> > EXPORT_SYMBOL(vfio_unpin_pages);
> >
> > +/*
> > + * Read/Write a range of userspace IOVAs for a device into/from a kernel
> > + * buffer without pinning the userspace memory
> > + * @dev [in] : device
> > + * @iova [in] : base IOVA of a userspace buffer
> > + * @data [in] : pointer to kernel buffer
> > + * @len [in] : kernel buffer length
> > + * @write : indicate read or write
> > + * Return error on failure or 0 on success.
> > + */
> > +int vfio_iova_rw(struct device *dev, unsigned long iova, void *data,
> > + unsigned long len, bool write)
>
> Shouldn't iova be a dma_addr_t and len be a size_t? AIUI this function
> performs the equivalent behavior of the device itself performing a DMA.
> Hmm, should the interface be named vfio_dma_rw()?
>
ok. will rename the interface to vfio_dma_rw(). thanks :)
> > +{
> > + struct vfio_container *container;
> > + struct vfio_group *group;
> > + struct vfio_iommu_driver *driver;
> > + int ret = 0;
> > +
> > + if (!dev || !data || len <= 0)
> > + return -EINVAL;
> > +
> > + group = vfio_group_get_from_dev(dev);
> > + if (!group)
> > + return -ENODEV;
> > +
> > + ret = vfio_group_add_container_user(group);
> > + if (ret)
> > + goto out;
> > +
> > + container = group->container;
> > + driver = container->iommu_driver;
> > +
> > + if (likely(driver && driver->ops->iova_rw))
> > + ret = driver->ops->iova_rw(container->iommu_data,
> > + iova, data, len, write);
> > + else
> > + ret = -ENOTTY;
> > +
> > + vfio_group_try_dissolve_container(group);
> > +out:
> > + vfio_group_put(group);
> > + return ret;
> > +}
> > +EXPORT_SYMBOL(vfio_iova_rw);
> > +
> > static int vfio_register_iommu_notifier(struct vfio_group *group,
> > unsigned long *events,
> > struct notifier_block *nb)
> > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> > index 2ada8e6cdb88..aee191077235 100644
> > --- a/drivers/vfio/vfio_iommu_type1.c
> > +++ b/drivers/vfio/vfio_iommu_type1.c
> > @@ -27,6 +27,7 @@
> > #include <linux/iommu.h>
> > #include <linux/module.h>
> > #include <linux/mm.h>
> > +#include <linux/mmu_context.h>
> > #include <linux/rbtree.h>
> > #include <linux/sched/signal.h>
> > #include <linux/sched/mm.h>
> > @@ -2326,6 +2327,85 @@ static int vfio_iommu_type1_unregister_notifier(void *iommu_data,
> > return blocking_notifier_chain_unregister(&iommu->notifier, nb);
> > }
> >
> > +static int next_segment(unsigned long len, int offset)
> > +{
> > + if (len > PAGE_SIZE - offset)
> > + return PAGE_SIZE - offset;
> > + else
> > + return len;
> > +}
> > +
> > +static int vfio_iommu_type1_rw_iova_seg(struct vfio_iommu *iommu,
> > + unsigned long iova, void *data,
> > + unsigned long seg_len,
> > + unsigned long offset,
> > + bool write)
> > +{
> > + struct mm_struct *mm;
> > + unsigned long vaddr;
> > + struct vfio_dma *dma;
> > + bool kthread = current->mm == NULL;
> > + int ret = 0;
> > +
> > + dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
> > + if (!dma)
> > + return -EINVAL;
> > +
> > + mm = get_task_mm(dma->task);
> > +
> > + if (!mm)
> > + return -ENODEV;
> > +
> > + if (kthread)
> > + use_mm(mm);
> > + else if (current->mm != mm) {
> > + ret = -EINVAL;
> > + goto out;
> > + }
> > +
> > + vaddr = dma->vaddr + iova - dma->iova + offset;
>
> Parenthesis here would be useful and might prevent overflow, ie:
>
> dma->vaddr + (iova - dma->iova) + offset
>
Yes, thanks for pointing it out!
> > +
> > + ret = write ? __copy_to_user((void __user *)vaddr,
> > + data, seg_len) :
> > + __copy_from_user(data, (void __user *)vaddr,
> > + seg_len);
> > + if (ret)
> > + ret = -EFAULT;
> > +
> > + if (kthread)
> > + unuse_mm(mm);
> > +out:
> > + mmput(mm);
> > + return ret;
> > +}
> > +
> > +static int vfio_iommu_type1_iova_rw(void *iommu_data, unsigned long iova,
> > + void *data, unsigned long len, bool write)
> > +{
> > + struct vfio_iommu *iommu = iommu_data;
> > + int offset = iova & ~PAGE_MASK;
> > + int seg_len;
> > + int ret = 0;
> > +
> > + iova = iova & PAGE_MASK;
> > +
> > + mutex_lock(&iommu->lock);
> > + while ((seg_len = next_segment(len, offset)) > 0) {
> > + ret = vfio_iommu_type1_rw_iova_seg(iommu, iova, data,
> > + seg_len, offset, write);
>
> Why do we need to split operations at page boundaries? It seems really
> inefficient that at each page crossing we need to lookup the vfio_dma
> again (probably the same one), switch to the mm (probably the same one),
> and perform another copy_{to,from}_user() when potentially have
> everything we need to perform a larger copy. Thanks,
>
you are right. Maybe I can first search dma with size of 1 and then
check the size of the found dma to perform a larger copy.
Thanks
Yan
>
> > + if (ret)
> > + break;
> > +
> > + offset = 0;
> > + len -= seg_len;
> > + data += seg_len;
> > + iova += PAGE_SIZE;
> > + }
> > +
> > + mutex_unlock(&iommu->lock);
> > + return ret;
> > +}
> > +
> > static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
> > .name = "vfio-iommu-type1",
> > .owner = THIS_MODULE,
> > @@ -2338,6 +2418,7 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
> > .unpin_pages = vfio_iommu_type1_unpin_pages,
> > .register_notifier = vfio_iommu_type1_register_notifier,
> > .unregister_notifier = vfio_iommu_type1_unregister_notifier,
> > + .iova_rw = vfio_iommu_type1_iova_rw,
> > };
> >
> > static int __init vfio_iommu_type1_init(void)
> > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> > index e42a711a2800..7bf18a31bbcf 100644
> > --- a/include/linux/vfio.h
> > +++ b/include/linux/vfio.h
> > @@ -82,6 +82,8 @@ struct vfio_iommu_driver_ops {
> > struct notifier_block *nb);
> > int (*unregister_notifier)(void *iommu_data,
> > struct notifier_block *nb);
> > + int (*iova_rw)(void *iommu_data, unsigned long iova,
> > + void *data, unsigned long len, bool write);
> > };
> >
> > extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
> > @@ -107,6 +109,9 @@ extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn,
> > extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
> > int npage);
> >
> > +extern int vfio_iova_rw(struct device *dev, unsigned long iova, void *data,
> > + unsigned long len, bool write);
> > +
> > /* each type has independent events */
> > enum vfio_notify_type {
> > VFIO_IOMMU_NOTIFY = 0,
>
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-01-10 3:33 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-01-03 1:00 [PATCH 0/2] use vfio_iova_rw() to read/write IOVAs from CPU side Yan Zhao
2020-01-03 1:02 ` [PATCH 1/2] vfio: introduce vfio_iova_rw to read/write a range of IOVAs Yan Zhao
2020-01-09 18:16 ` Alex Williamson
2020-01-10 3:24 ` Yan Zhao
2020-01-03 1:03 ` [PATCH 2/2] drm/i915/gvt: subsitute kvm_read/write_guest with vfio_iova_rw Yan Zhao
2020-01-07 10:21 ` Paolo Bonzini
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