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Date: Tue, 12 Feb 2013 10:15:04 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: Alexey Kardashevskiy <aik@...abs.ru>
Cc: Joerg Roedel <joerg.roedel@....com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
linux-kernel@...r.kernel.org,
David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH] iommu: making IOMMU sysfs nodes API public
On Wed, 2013-02-13 at 01:42 +1100, Alexey Kardashevskiy wrote:
> On 12/02/13 16:07, Alex Williamson wrote:
> > On Tue, 2013-02-12 at 15:06 +1100, Alexey Kardashevskiy wrote:
> >> Having this patch in a tree, adding new nodes in sysfs
> >> for IOMMU groups is going to be easier.
> >>
> >> The first candidate for this change is a "dma-window-size"
> >> property which tells a size of a DMA window of the specific
> >> IOMMU group which can be used later for locked pages accounting.
> >
> > I'm still churning on this one; I'm nervous this would basically creat
> > a /proc free-for-all under /sys/kernel/iommu_group/$GROUP/ where any
> > iommu driver can add random attributes. That can get ugly for
> > userspace.
>
> Is not it exactly what sysfs is for (unlike /proc)? :)
Um, I hope it's a little more thought out than /proc.
> > On the other hand, for the application of userspace knowing how much
> > memory to lock for vfio use of a group, it's an appealing location to
> > get that information. Something like libvirt would already be poking
> > around here to figure out which devices to bind. Page limits need to be
> > setup prior to use through vfio, so sysfs is more convenient than
> > through vfio ioctls.
>
> True. DMA window properties do not change since boot so sysfs is the right
> place to expose them.
>
> > But then is dma-window-size just a vfio requirement leaking over into
> > iommu groups? Can we allow iommu driver based attributes without giving
> > up control of the namespace? Thanks,
>
> Who are you asking these questions? :)
Anyone, including you. Rather than dropping misc files in sysfs to
describe things about the group, I think the better solution in your
case might be a link from the group to an existing sysfs directory
describing the PE. I believe your PE is rooted in a PCI bridge, so that
presumably already has a representation in sysfs. Can the aperture size
be determined from something in sysfs for that bridge already? I'm just
not ready to create a grab bag of sysfs entries for a group yet.
Thanks,
Alex
> >> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
> >> ---
> >> drivers/iommu/iommu.c | 19 ++-----------------
> >> include/linux/iommu.h | 20 ++++++++++++++++++++
> >> 2 files changed, 22 insertions(+), 17 deletions(-)
> >>
> >> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> >> index b0afd3d..58cc298 100644
> >> --- a/drivers/iommu/iommu.c
> >> +++ b/drivers/iommu/iommu.c
> >> @@ -52,22 +52,6 @@ struct iommu_device {
> >> char *name;
> >> };
> >>
> >> -struct iommu_group_attribute {
> >> - struct attribute attr;
> >> - ssize_t (*show)(struct iommu_group *group, char *buf);
> >> - ssize_t (*store)(struct iommu_group *group,
> >> - const char *buf, size_t count);
> >> -};
> >> -
> >> -#define IOMMU_GROUP_ATTR(_name, _mode, _show, _store) \
> >> -struct iommu_group_attribute iommu_group_attr_##_name = \
> >> - __ATTR(_name, _mode, _show, _store)
> >> -
> >> -#define to_iommu_group_attr(_attr) \
> >> - container_of(_attr, struct iommu_group_attribute, attr)
> >> -#define to_iommu_group(_kobj) \
> >> - container_of(_kobj, struct iommu_group, kobj)
> >> -
> >> static ssize_t iommu_group_attr_show(struct kobject *kobj,
> >> struct attribute *__attr, char *buf)
> >> {
> >> @@ -98,11 +82,12 @@ static const struct sysfs_ops iommu_group_sysfs_ops = {
> >> .store = iommu_group_attr_store,
> >> };
> >>
> >> -static int iommu_group_create_file(struct iommu_group *group,
> >> +int iommu_group_create_file(struct iommu_group *group,
> >> struct iommu_group_attribute *attr)
> >> {
> >> return sysfs_create_file(&group->kobj, &attr->attr);
> >> }
> >> +EXPORT_SYMBOL_GPL(iommu_group_create_file);
> >>
> >> static void iommu_group_remove_file(struct iommu_group *group,
> >> struct iommu_group_attribute *attr)
> >> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> >> index f3b99e1..6d24ba7 100644
> >> --- a/include/linux/iommu.h
> >> +++ b/include/linux/iommu.h
> >> @@ -21,6 +21,7 @@
> >>
> >> #include <linux/errno.h>
> >> #include <linux/types.h>
> >> +#include <linux/stat.h>
> >>
> >> #define IOMMU_READ (1)
> >> #define IOMMU_WRITE (2)
> >> @@ -197,6 +198,25 @@ static inline int report_iommu_fault(struct iommu_domain *domain,
> >> return ret;
> >> }
> >>
> >> +struct iommu_group_attribute {
> >> + struct attribute attr;
> >> + ssize_t (*show)(struct iommu_group *group, char *buf);
> >> + ssize_t (*store)(struct iommu_group *group,
> >> + const char *buf, size_t count);
> >> +};
> >> +
> >> +#define IOMMU_GROUP_ATTR(_name, _mode, _show, _store) \
> >> +struct iommu_group_attribute iommu_group_attr_##_name = \
> >> + __ATTR(_name, _mode, _show, _store)
> >> +
> >> +#define to_iommu_group_attr(_attr) \
> >> + container_of(_attr, struct iommu_group_attribute, attr)
> >> +#define to_iommu_group(_kobj) \
> >> + container_of(_kobj, struct iommu_group, kobj)
> >> +
> >> +extern int iommu_group_create_file(struct iommu_group *group,
> >> + struct iommu_group_attribute *attr);
> >> +
> >> #else /* CONFIG_IOMMU_API */
> >>
> >> struct iommu_ops {};
> >
> >
> >
>
>
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