Re: [PATCH] iommu: Improve the performance for direct_mapping
On Thu, 2020-11-26 at 15:19 +, Robin Murphy wrote:
> On 2020-11-20 09:06, Yong Wu wrote:
> > Currently direct_mapping always use the smallest pgsize which is SZ_4K
> > normally to mapping. This is unnecessary. we could gather the size, and
> > call iommu_map then, iommu_map could decide how to map better with the
> > just right pgsize.
> >
> > From the original comment, we should take care overlap, otherwise,
> > iommu_map may return -EEXIST. In this overlap case, we should map the
> > previous region before overlap firstly. then map the left part.
> >
> > Each a iommu device will call this direct_mapping when its iommu
> > initialize, This patch is effective to improve the boot/initialization
> > time especially while it only needs level 1 mapping.
> >
> > Signed-off-by: Anan Sun
> > Signed-off-by: Yong Wu
> > ---
> > drivers/iommu/iommu.c | 20 ++--
> > 1 file changed, 18 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index df87c8e825f7..854a8fcb928d 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -737,6 +737,7 @@ static int iommu_create_device_direct_mappings(struct
> > iommu_group *group,
> > /* We need to consider overlapping regions for different devices */
> > list_for_each_entry(entry, , list) {
> > dma_addr_t start, end, addr;
> > + size_t unmapped_sz = 0;
> >
> > if (domain->ops->apply_resv_region)
> > domain->ops->apply_resv_region(dev, domain, entry);
> > @@ -752,10 +753,25 @@ static int iommu_create_device_direct_mappings(struct
> > iommu_group *group,
> > phys_addr_t phys_addr;
> >
> > phys_addr = iommu_iova_to_phys(domain, addr);
> > - if (phys_addr)
> > + if (phys_addr == 0) {
> > + unmapped_sz += pg_size; /* Gather the size. */
> > continue;
> > + }
>
> I guess the reason we need to validate every page is because they may
> already have been legitimately mapped if someone else's reserved region
> overlaps - is it worth explicitly validating that, i.e. bail out if
> something's gone wrong enough that phys_addr != addr?
I'm not sure the history about why to validate every page. this
direct_mapping is called very early, normally after alloc_default_domain
and _attach_device. the "phys_addr != addr" looks impossible.
If there is a normal flow that may cause "phys_addr != addr", then
something go wrong, Could we give a warning like adding a
WARN_ON_ONCE(phys_addr != addr)? and it should be in a another patch.
>
> Other than the naming issue (I agree that map_size is a far, far better
> choice), I don't have any strong opinions about the rest of the
> implementation - I've written enough variations of this pattern to know
> that there's just no "nice" way to do it in C; all you can do is shuffle
> the clunkiness around :)
:). I will send a v2.
Thanks.
>
> Robin.
>
> >
> > - ret = iommu_map(domain, addr, addr, pg_size,
> > entry->prot);
> > + if (unmapped_sz) {
> > + /* Map the region before the overlap. */
> > + ret = iommu_map(domain, start, start,
> > + unmapped_sz, entry->prot);
> > + if (ret)
> > + goto out;
> > + start += unmapped_sz;
> > + unmapped_sz = 0;
> > + }
> > + start += pg_size;
> > + }
> > + if (unmapped_sz) {
> > + ret = iommu_map(domain, start, start, unmapped_sz,
> > + entry->prot);
> > if (ret)
> > goto out;
> > }
> >
>
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> http://lists.infradead.org/mailman/listinfo/linux-mediatek
Re: [PATCH] iommu: Improve the performance for direct_mapping
On 2020-11-20 09:06, Yong Wu wrote:
Currently direct_mapping always use the smallest pgsize which is SZ_4K
normally to mapping. This is unnecessary. we could gather the size, and
call iommu_map then, iommu_map could decide how to map better with the
just right pgsize.
From the original comment, we should take care overlap, otherwise,
iommu_map may return -EEXIST. In this overlap case, we should map the
previous region before overlap firstly. then map the left part.
Each a iommu device will call this direct_mapping when its iommu
initialize, This patch is effective to improve the boot/initialization
time especially while it only needs level 1 mapping.
Signed-off-by: Anan Sun
Signed-off-by: Yong Wu
---
drivers/iommu/iommu.c | 20 ++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index df87c8e825f7..854a8fcb928d 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -737,6 +737,7 @@ static int iommu_create_device_direct_mappings(struct
iommu_group *group,
/* We need to consider overlapping regions for different devices */
list_for_each_entry(entry, , list) {
dma_addr_t start, end, addr;
+ size_t unmapped_sz = 0;
if (domain->ops->apply_resv_region)
domain->ops->apply_resv_region(dev, domain, entry);
@@ -752,10 +753,25 @@ static int iommu_create_device_direct_mappings(struct
iommu_group *group,
phys_addr_t phys_addr;
phys_addr = iommu_iova_to_phys(domain, addr);
- if (phys_addr)
+ if (phys_addr == 0) {
+ unmapped_sz += pg_size; /* Gather the size. */
continue;
+ }
I guess the reason we need to validate every page is because they may
already have been legitimately mapped if someone else's reserved region
overlaps - is it worth explicitly validating that, i.e. bail out if
something's gone wrong enough that phys_addr != addr?
Other than the naming issue (I agree that map_size is a far, far better
choice), I don't have any strong opinions about the rest of the
implementation - I've written enough variations of this pattern to know
that there's just no "nice" way to do it in C; all you can do is shuffle
the clunkiness around :)
Robin.
- ret = iommu_map(domain, addr, addr, pg_size, entry->prot);
+ if (unmapped_sz) {
+ /* Map the region before the overlap. */
+ ret = iommu_map(domain, start, start,
+ unmapped_sz, entry->prot);
+ if (ret)
+ goto out;
+ start += unmapped_sz;
+ unmapped_sz = 0;
+ }
+ start += pg_size;
+ }
+ if (unmapped_sz) {
+ ret = iommu_map(domain, start, start, unmapped_sz,
+ entry->prot);
if (ret)
goto out;
}
Re: [PATCH] iommu: Improve the performance for direct_mapping
On Wed, Nov 25, 2020 at 07:03:34PM +0800, Yong Wu wrote:
> On Tue, 2020-11-24 at 11:05 +, Will Deacon wrote:
> > On Tue, Nov 24, 2020 at 05:24:44PM +0800, Yong Wu wrote:
> > > On Mon, 2020-11-23 at 12:32 +, Will Deacon wrote:
> > That said, maybe we could simplify this further by changing the loop bounds
> > to be:
> >
> > for (addr = start; addr <= end; addr += pg_size)
> >
> > and checking:
> >
> > if (!phys_addr && addr != end) {
> > map_size += pg_size;
> > continue;
> > }
> >
> > does that work?
>
> It works but I think we can not check iommu_iova_to_phys(domain, end).
> We should add a "if", like:
>
> for (addr = start; addr <= end; addr += pg_size) {
> ...
> if (addr < end) {
> phys_addr = iommu_iova_to_phys(domain, addr);
> if (!phys_addr) {
> map_size += pg_size;
> continue;
> }
> }
> ...
>
Oh yes, you're right.
> If you don't like this "if (addr < end)", then we have to add a "goto".
> like this:
>
>
> for (addr = start; addr <= end; addr += pg_size) {
> phys_addr_t phys_addr;
>
> if (addr == end)
> goto map_last;
>
> phys_addr = iommu_iova_to_phys(domain, addr);
> if (!phys_addr) {
> map_size += pg_size;
> continue;
> }
>
> map_last:
> if (!map_size)
> continue;
> ret = iommu_map(domain, addr - map_size,
> addr - map_size, map_size, entry->prot);
I think it's cleared to invert this as you had before:
if (map_size)
ret = iommu_map(...);
> Which one is better?
The second one is easier to read. I'll stop making suggestions now, thanks.
Will
Re: [PATCH] iommu: Improve the performance for direct_mapping
On Tue, 2020-11-24 at 11:05 +, Will Deacon wrote:
> On Tue, Nov 24, 2020 at 05:24:44PM +0800, Yong Wu wrote:
> > On Mon, 2020-11-23 at 12:32 +, Will Deacon wrote:
> > > On Fri, Nov 20, 2020 at 05:06:28PM +0800, Yong Wu wrote:
> > > > + unmapped_sz = 0;
> > > > + }
> > > > + start += pg_size;
> > > > + }
> > > > + if (unmapped_sz) {
> > > > + ret = iommu_map(domain, start, start,
> > > > unmapped_sz,
> > > > + entry->prot);
> > >
> > > Can you avoid this hunk by changing your loop check to something like:
> > >
> > > if (!phys_addr) {
> > > map_size += pg_size;
> > > if (addr + pg_size < end)
> > > continue;
> > > }
> >
> > Thanks for your quick review. I have fixed and tested it. the patch is
> > simple. I copy it here. Is this readable for you now?
> >
> >
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -737,6 +737,7 @@ static int
> > iommu_create_device_direct_mappings(struct iommu_group *group,
> > /* We need to consider overlapping regions for different devices */
> > list_for_each_entry(entry, , list) {
> > dma_addr_t start, end, addr;
> > + size_t map_size = 0;
> >
> > if (domain->ops->apply_resv_region)
> > domain->ops->apply_resv_region(dev, domain, entry);
> > @@ -752,12 +753,21 @@ static int
> > iommu_create_device_direct_mappings(struct iommu_group *group,
> > phys_addr_t phys_addr;
> >
> > phys_addr = iommu_iova_to_phys(domain, addr);
> > - if (phys_addr)
> > - continue;
> > + if (!phys_addr) {
> > + map_size += pg_size;
> > + if (addr + pg_size < end)
> > + continue;
> > + else
>
> You don't need the 'else' here ^^^
>
> > + addr += pg_size; /*Point to End */
>
> addr = end ?
>
> That said, maybe we could simplify this further by changing the loop bounds
> to be:
>
> for (addr = start; addr <= end; addr += pg_size)
>
> and checking:
>
> if (!phys_addr && addr != end) {
> map_size += pg_size;
> continue;
> }
>
> does that work?
It works but I think we can not check iommu_iova_to_phys(domain, end).
We should add a "if", like:
for (addr = start; addr <= end; addr += pg_size) {
...
if (addr < end) {
phys_addr = iommu_iova_to_phys(domain, addr);
if (!phys_addr) {
map_size += pg_size;
continue;
}
}
...
If you don't like this "if (addr < end)", then we have to add a "goto".
like this:
for (addr = start; addr <= end; addr += pg_size) {
phys_addr_t phys_addr;
if (addr == end)
goto map_last;
phys_addr = iommu_iova_to_phys(domain, addr);
if (!phys_addr) {
map_size += pg_size;
continue;
}
map_last:
if (!map_size)
continue;
ret = iommu_map(domain, addr - map_size,
addr - map_size, map_size, entry->prot);
if (ret)
goto out;
}
Which one is better?
>
> Will
>
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> Linux-mediatek mailing list
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Re: [PATCH] iommu: Improve the performance for direct_mapping
On Tue, Nov 24, 2020 at 05:24:44PM +0800, Yong Wu wrote:
> On Mon, 2020-11-23 at 12:32 +, Will Deacon wrote:
> > On Fri, Nov 20, 2020 at 05:06:28PM +0800, Yong Wu wrote:
> > > + unmapped_sz = 0;
> > > + }
> > > + start += pg_size;
> > > + }
> > > + if (unmapped_sz) {
> > > + ret = iommu_map(domain, start, start, unmapped_sz,
> > > + entry->prot);
> >
> > Can you avoid this hunk by changing your loop check to something like:
> >
> > if (!phys_addr) {
> > map_size += pg_size;
> > if (addr + pg_size < end)
> > continue;
> > }
>
> Thanks for your quick review. I have fixed and tested it. the patch is
> simple. I copy it here. Is this readable for you now?
>
>
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -737,6 +737,7 @@ static int
> iommu_create_device_direct_mappings(struct iommu_group *group,
> /* We need to consider overlapping regions for different devices */
> list_for_each_entry(entry, , list) {
> dma_addr_t start, end, addr;
> + size_t map_size = 0;
>
> if (domain->ops->apply_resv_region)
> domain->ops->apply_resv_region(dev, domain, entry);
> @@ -752,12 +753,21 @@ static int
> iommu_create_device_direct_mappings(struct iommu_group *group,
> phys_addr_t phys_addr;
>
> phys_addr = iommu_iova_to_phys(domain, addr);
> - if (phys_addr)
> - continue;
> + if (!phys_addr) {
> + map_size += pg_size;
> + if (addr + pg_size < end)
> + continue;
> + else
You don't need the 'else' here ^^^
> + addr += pg_size; /*Point to End */
addr = end ?
That said, maybe we could simplify this further by changing the loop bounds
to be:
for (addr = start; addr <= end; addr += pg_size)
and checking:
if (!phys_addr && addr != end) {
map_size += pg_size;
continue;
}
does that work?
Will
Re: [PATCH] iommu: Improve the performance for direct_mapping
On Mon, 2020-11-23 at 12:32 +, Will Deacon wrote:
> On Fri, Nov 20, 2020 at 05:06:28PM +0800, Yong Wu wrote:
> > Currently direct_mapping always use the smallest pgsize which is SZ_4K
> > normally to mapping. This is unnecessary. we could gather the size, and
> > call iommu_map then, iommu_map could decide how to map better with the
> > just right pgsize.
> >
> > From the original comment, we should take care overlap, otherwise,
> > iommu_map may return -EEXIST. In this overlap case, we should map the
> > previous region before overlap firstly. then map the left part.
> >
> > Each a iommu device will call this direct_mapping when its iommu
> > initialize, This patch is effective to improve the boot/initialization
> > time especially while it only needs level 1 mapping.
> >
> > Signed-off-by: Anan Sun
> > Signed-off-by: Yong Wu
> > ---
> > drivers/iommu/iommu.c | 20 ++--
> > 1 file changed, 18 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index df87c8e825f7..854a8fcb928d 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -737,6 +737,7 @@ static int iommu_create_device_direct_mappings(struct
> > iommu_group *group,
> > /* We need to consider overlapping regions for different devices */
> > list_for_each_entry(entry, , list) {
> > dma_addr_t start, end, addr;
> > + size_t unmapped_sz = 0;
>
> I think "unmapped" is the wrong word here, as this variable actually
> represents the amount we want to map! I suggest "map_size" instead.
>
> > if (domain->ops->apply_resv_region)
> > domain->ops->apply_resv_region(dev, domain, entry);
> > @@ -752,10 +753,25 @@ static int iommu_create_device_direct_mappings(struct
> > iommu_group *group,
> > phys_addr_t phys_addr;
> >
> > phys_addr = iommu_iova_to_phys(domain, addr);
> > - if (phys_addr)
> > + if (phys_addr == 0) {
> > + unmapped_sz += pg_size; /* Gather the size. */
> > continue;
> > + }
> >
> > - ret = iommu_map(domain, addr, addr, pg_size,
> > entry->prot);
> > + if (unmapped_sz) {
> > + /* Map the region before the overlap. */
> > + ret = iommu_map(domain, start, start,
> > + unmapped_sz, entry->prot);
> > + if (ret)
> > + goto out;
> > + start += unmapped_sz;
>
> I think it's a bit confusing to update start like this. Can we call
> iommu_map(domain, addr - map_size, addr - map_size, map_size, entry->prot)
> instead?
>
> > + unmapped_sz = 0;
> > + }
> > + start += pg_size;
> > + }
> > + if (unmapped_sz) {
> > + ret = iommu_map(domain, start, start, unmapped_sz,
> > + entry->prot);
>
> Can you avoid this hunk by changing your loop check to something like:
>
> if (!phys_addr) {
> map_size += pg_size;
> if (addr + pg_size < end)
> continue;
> }
Thanks for your quick review. I have fixed and tested it. the patch is
simple. I copy it here. Is this readable for you now?
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -737,6 +737,7 @@ static int
iommu_create_device_direct_mappings(struct iommu_group *group,
/* We need to consider overlapping regions for different devices */
list_for_each_entry(entry, , list) {
dma_addr_t start, end, addr;
+ size_t map_size = 0;
if (domain->ops->apply_resv_region)
domain->ops->apply_resv_region(dev, domain, entry);
@@ -752,12 +753,21 @@ static int
iommu_create_device_direct_mappings(struct iommu_group *group,
phys_addr_t phys_addr;
phys_addr = iommu_iova_to_phys(domain, addr);
- if (phys_addr)
- continue;
+ if (!phys_addr) {
+ map_size += pg_size;
+ if (addr + pg_size < end)
+ continue;
+ else
+ addr += pg_size; /*Point to End */
+ }
- ret = iommu_map(domain, addr, addr, pg_size,
entry->prot);
- if (ret)
- goto out;
+ if (map_size) {
+ ret = iommu_map(domain, addr - map_size, addr -
map_size,
+ map_size, entry->prot);
+
Re: [PATCH] iommu: Improve the performance for direct_mapping
On Fri, Nov 20, 2020 at 05:06:28PM +0800, Yong Wu wrote:
> Currently direct_mapping always use the smallest pgsize which is SZ_4K
> normally to mapping. This is unnecessary. we could gather the size, and
> call iommu_map then, iommu_map could decide how to map better with the
> just right pgsize.
>
> From the original comment, we should take care overlap, otherwise,
> iommu_map may return -EEXIST. In this overlap case, we should map the
> previous region before overlap firstly. then map the left part.
>
> Each a iommu device will call this direct_mapping when its iommu
> initialize, This patch is effective to improve the boot/initialization
> time especially while it only needs level 1 mapping.
>
> Signed-off-by: Anan Sun
> Signed-off-by: Yong Wu
> ---
> drivers/iommu/iommu.c | 20 ++--
> 1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index df87c8e825f7..854a8fcb928d 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -737,6 +737,7 @@ static int iommu_create_device_direct_mappings(struct
> iommu_group *group,
> /* We need to consider overlapping regions for different devices */
> list_for_each_entry(entry, , list) {
> dma_addr_t start, end, addr;
> + size_t unmapped_sz = 0;
I think "unmapped" is the wrong word here, as this variable actually
represents the amount we want to map! I suggest "map_size" instead.
> if (domain->ops->apply_resv_region)
> domain->ops->apply_resv_region(dev, domain, entry);
> @@ -752,10 +753,25 @@ static int iommu_create_device_direct_mappings(struct
> iommu_group *group,
> phys_addr_t phys_addr;
>
> phys_addr = iommu_iova_to_phys(domain, addr);
> - if (phys_addr)
> + if (phys_addr == 0) {
> + unmapped_sz += pg_size; /* Gather the size. */
> continue;
> + }
>
> - ret = iommu_map(domain, addr, addr, pg_size,
> entry->prot);
> + if (unmapped_sz) {
> + /* Map the region before the overlap. */
> + ret = iommu_map(domain, start, start,
> + unmapped_sz, entry->prot);
> + if (ret)
> + goto out;
> + start += unmapped_sz;
I think it's a bit confusing to update start like this. Can we call
iommu_map(domain, addr - map_size, addr - map_size, map_size, entry->prot)
instead?
> + unmapped_sz = 0;
> + }
> + start += pg_size;
> + }
> + if (unmapped_sz) {
> + ret = iommu_map(domain, start, start, unmapped_sz,
> + entry->prot);
Can you avoid this hunk by changing your loop check to something like:
if (!phys_addr) {
map_size += pg_size;
if (addr + pg_size < end)
continue;
}
Will
[PATCH] iommu: Improve the performance for direct_mapping
Currently direct_mapping always use the smallest pgsize which is SZ_4K
normally to mapping. This is unnecessary. we could gather the size, and
call iommu_map then, iommu_map could decide how to map better with the
just right pgsize.
>From the original comment, we should take care overlap, otherwise,
iommu_map may return -EEXIST. In this overlap case, we should map the
previous region before overlap firstly. then map the left part.
Each a iommu device will call this direct_mapping when its iommu
initialize, This patch is effective to improve the boot/initialization
time especially while it only needs level 1 mapping.
Signed-off-by: Anan Sun
Signed-off-by: Yong Wu
---
drivers/iommu/iommu.c | 20 ++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index df87c8e825f7..854a8fcb928d 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -737,6 +737,7 @@ static int iommu_create_device_direct_mappings(struct
iommu_group *group,
/* We need to consider overlapping regions for different devices */
list_for_each_entry(entry, , list) {
dma_addr_t start, end, addr;
+ size_t unmapped_sz = 0;
if (domain->ops->apply_resv_region)
domain->ops->apply_resv_region(dev, domain, entry);
@@ -752,10 +753,25 @@ static int iommu_create_device_direct_mappings(struct
iommu_group *group,
phys_addr_t phys_addr;
phys_addr = iommu_iova_to_phys(domain, addr);
- if (phys_addr)
+ if (phys_addr == 0) {
+ unmapped_sz += pg_size; /* Gather the size. */
continue;
+ }
- ret = iommu_map(domain, addr, addr, pg_size,
entry->prot);
+ if (unmapped_sz) {
+ /* Map the region before the overlap. */
+ ret = iommu_map(domain, start, start,
+ unmapped_sz, entry->prot);
+ if (ret)
+ goto out;
+ start += unmapped_sz;
+ unmapped_sz = 0;
+ }
+ start += pg_size;
+ }
+ if (unmapped_sz) {
+ ret = iommu_map(domain, start, start, unmapped_sz,
+ entry->prot);
if (ret)
goto out;
}
--
2.18.0
