[08/16] iommu/fsl: use page allocation function provided by iommu-pages.h

  Convert iommu/fsl_pamu.c to use the new page allocation functions
provided in iommu-pages.h.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 drivers/iommu/fsl_pamu.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
  

On 2023-11-28 8:49 pm, Pasha Tatashin wrote:
> Convert iommu/fsl_pamu.c to use the new page allocation functions
> provided in iommu-pages.h.

Again, this is not a pagetable. This thing doesn't even *have* pagetables.

Similar to patches #1 and #2 where you're lumping in configuration 
tables which belong to the IOMMU driver itself, as opposed to pagetables 
which effectively belong to an IOMMU domain's user. But then there are 
still drivers where you're *not* accounting similar configuration 
structures, so I really struggle to see how this metric is useful when 
it's so completely inconsistent in what it's counting :/

Thanks,
Robin.

> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> ---
>   drivers/iommu/fsl_pamu.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iommu/fsl_pamu.c b/drivers/iommu/fsl_pamu.c
> index f37d3b044131..7bfb49940f0c 100644
> --- a/drivers/iommu/fsl_pamu.c
> +++ b/drivers/iommu/fsl_pamu.c
> @@ -16,6 +16,7 @@
>   #include <linux/platform_device.h>
>   
>   #include <asm/mpc85xx.h>
> +#include "iommu-pages.h"
>   
>   /* define indexes for each operation mapping scenario */
>   #define OMI_QMAN        0x00
> @@ -828,7 +829,7 @@ static int fsl_pamu_probe(struct platform_device *pdev)
>   		(PAGE_SIZE << get_order(OMT_SIZE));
>   	order = get_order(mem_size);
>   
> -	p = alloc_pages(GFP_KERNEL | __GFP_ZERO, order);
> +	p = __iommu_alloc_pages(GFP_KERNEL, order);
>   	if (!p) {
>   		dev_err(dev, "unable to allocate PAACT/SPAACT/OMT block\n");
>   		ret = -ENOMEM;
> @@ -916,7 +917,7 @@ static int fsl_pamu_probe(struct platform_device *pdev)
>   		iounmap(guts_regs);
>   
>   	if (ppaact)
> -		free_pages((unsigned long)ppaact, order);
> +		iommu_free_pages(ppaact, order);
>   
>   	ppaact = NULL;
>
  

On Tue, Nov 28, 2023 at 5:53 PM Robin Murphy <robin.murphy@arm.com> wrote:
>
> On 2023-11-28 8:49 pm, Pasha Tatashin wrote:
> > Convert iommu/fsl_pamu.c to use the new page allocation functions
> > provided in iommu-pages.h.
>
> Again, this is not a pagetable. This thing doesn't even *have* pagetables.
>
> Similar to patches #1 and #2 where you're lumping in configuration
> tables which belong to the IOMMU driver itself, as opposed to pagetables
> which effectively belong to an IOMMU domain's user. But then there are
> still drivers where you're *not* accounting similar configuration
> structures, so I really struggle to see how this metric is useful when
> it's so completely inconsistent in what it's counting :/

The whole IOMMU subsystem allocates a significant amount of kernel
locked memory that we want to at least observe. The new field in
vmstat does just that: it reports ALL buddy allocator memory that
IOMMU allocates. However, for accounting purposes, I agree, we need to
do better, and separate at least iommu pagetables from the rest.

We can separate the metric into two:
iommu pagetable only
iommu everything

or into three:
iommu pagetable only
iommu dma
iommu everything

What do you think?

Pasha

>
> Thanks,
> Robin.
>
> > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> > ---
> >   drivers/iommu/fsl_pamu.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iommu/fsl_pamu.c b/drivers/iommu/fsl_pamu.c
> > index f37d3b044131..7bfb49940f0c 100644
> > --- a/drivers/iommu/fsl_pamu.c
> > +++ b/drivers/iommu/fsl_pamu.c
> > @@ -16,6 +16,7 @@
> >   #include <linux/platform_device.h>
> >
> >   #include <asm/mpc85xx.h>
> > +#include "iommu-pages.h"
> >
> >   /* define indexes for each operation mapping scenario */
> >   #define OMI_QMAN        0x00
> > @@ -828,7 +829,7 @@ static int fsl_pamu_probe(struct platform_device *pdev)
> >               (PAGE_SIZE << get_order(OMT_SIZE));
> >       order = get_order(mem_size);
> >
> > -     p = alloc_pages(GFP_KERNEL | __GFP_ZERO, order);
> > +     p = __iommu_alloc_pages(GFP_KERNEL, order);
> >       if (!p) {
> >               dev_err(dev, "unable to allocate PAACT/SPAACT/OMT block\n");
> >               ret = -ENOMEM;
> > @@ -916,7 +917,7 @@ static int fsl_pamu_probe(struct platform_device *pdev)
> >               iounmap(guts_regs);
> >
> >       if (ppaact)
> > -             free_pages((unsigned long)ppaact, order);
> > +             iommu_free_pages(ppaact, order);
> >
> >       ppaact = NULL;
> >
  

On Tue, Nov 28, 2023 at 06:00:13PM -0500, Pasha Tatashin wrote:
> On Tue, Nov 28, 2023 at 5:53 PM Robin Murphy <robin.murphy@arm.com> wrote:
> >
> > On 2023-11-28 8:49 pm, Pasha Tatashin wrote:
> > > Convert iommu/fsl_pamu.c to use the new page allocation functions
> > > provided in iommu-pages.h.
> >
> > Again, this is not a pagetable. This thing doesn't even *have* pagetables.
> >
> > Similar to patches #1 and #2 where you're lumping in configuration
> > tables which belong to the IOMMU driver itself, as opposed to pagetables
> > which effectively belong to an IOMMU domain's user. But then there are
> > still drivers where you're *not* accounting similar configuration
> > structures, so I really struggle to see how this metric is useful when
> > it's so completely inconsistent in what it's counting :/
> 
> The whole IOMMU subsystem allocates a significant amount of kernel
> locked memory that we want to at least observe. The new field in
> vmstat does just that: it reports ALL buddy allocator memory that
> IOMMU allocates. However, for accounting purposes, I agree, we need to
> do better, and separate at least iommu pagetables from the rest.
> 
> We can separate the metric into two:
> iommu pagetable only
> iommu everything
> 
> or into three:
> iommu pagetable only
> iommu dma
> iommu everything
> 
> What do you think?

I think I said this at LPC - if you want to have fine grained
accounting of memory by owner you need to go talk to the cgroup people
and come up with something generic. Adding ever open coded finer
category breakdowns just for iommu doesn't make alot of sense.

You can make some argument that the pagetable memory should be counted
because kvm counts it's shadow memory, but I wouldn't go into further
detail than that with hand coded counters..

Jason
  

On 28/11/2023 11:50 pm, Jason Gunthorpe wrote:
> On Tue, Nov 28, 2023 at 06:00:13PM -0500, Pasha Tatashin wrote:
>> On Tue, Nov 28, 2023 at 5:53 PM Robin Murphy <robin.murphy@arm.com> wrote:
>>>
>>> On 2023-11-28 8:49 pm, Pasha Tatashin wrote:
>>>> Convert iommu/fsl_pamu.c to use the new page allocation functions
>>>> provided in iommu-pages.h.
>>>
>>> Again, this is not a pagetable. This thing doesn't even *have* pagetables.
>>>
>>> Similar to patches #1 and #2 where you're lumping in configuration
>>> tables which belong to the IOMMU driver itself, as opposed to pagetables
>>> which effectively belong to an IOMMU domain's user. But then there are
>>> still drivers where you're *not* accounting similar configuration
>>> structures, so I really struggle to see how this metric is useful when
>>> it's so completely inconsistent in what it's counting :/
>>
>> The whole IOMMU subsystem allocates a significant amount of kernel
>> locked memory that we want to at least observe. The new field in
>> vmstat does just that: it reports ALL buddy allocator memory that
>> IOMMU allocates. However, for accounting purposes, I agree, we need to
>> do better, and separate at least iommu pagetables from the rest.
>>
>> We can separate the metric into two:
>> iommu pagetable only
>> iommu everything
>>
>> or into three:
>> iommu pagetable only
>> iommu dma
>> iommu everything
>>
>> What do you think?
> 
> I think I said this at LPC - if you want to have fine grained
> accounting of memory by owner you need to go talk to the cgroup people
> and come up with something generic. Adding ever open coded finer
> category breakdowns just for iommu doesn't make alot of sense.
> 
> You can make some argument that the pagetable memory should be counted
> because kvm counts it's shadow memory, but I wouldn't go into further
> detail than that with hand coded counters..

Right, pagetable memory is interesting since it's something that any 
random kernel user can indirectly allocate via iommu_domain_alloc() and 
iommu_map(), and some of those users may even be doing so on behalf of 
userspace. I have no objection to accounting and potentially applying 
limits to *that*.

Beyond that, though, there is nothing special about "the IOMMU 
subsystem". The amount of memory an IOMMU driver needs to allocate for 
itself in order to function is not of interest beyond curiosity, it just 
is what it is; limiting it would only break the IOMMU, and if a user 
thinks it's "too much", the only actionable thing that might help is to 
physically remove devices from the system. Similar for DMA buffers; it 
might be intriguing to account those, but it's not really an actionable 
metric - in the overwhelming majority of cases you can't simply tell a 
driver to allocate less than what it needs. And that is of course 
assuming if we were to account *all* DMA buffers, since whether they 
happen to have an IOMMU translation or not is irrelevant (we'd have 
already accounted the pagetables as pagetables if so).

I bet "the networking subsystem" also consumes significant memory on the 
same kind of big systems where IOMMU pagetables would be of any concern. 
I believe some of the some of the "serious" NICs can easily run up 
hundreds of megabytes if not gigabytes worth of queues, SKB pools, etc. 
- would you propose accounting those too?

Thanks,
Robin.
  

> >> We can separate the metric into two:
> >> iommu pagetable only
> >> iommu everything
> >>
> >> or into three:
> >> iommu pagetable only
> >> iommu dma
> >> iommu everything
> >>
> >> What do you think?
> >
> > I think I said this at LPC - if you want to have fine grained
> > accounting of memory by owner you need to go talk to the cgroup people
> > and come up with something generic. Adding ever open coded finer
> > category breakdowns just for iommu doesn't make alot of sense.
> >
> > You can make some argument that the pagetable memory should be counted
> > because kvm counts it's shadow memory, but I wouldn't go into further
> > detail than that with hand coded counters..
>
> Right, pagetable memory is interesting since it's something that any
> random kernel user can indirectly allocate via iommu_domain_alloc() and
> iommu_map(), and some of those users may even be doing so on behalf of
> userspace. I have no objection to accounting and potentially applying
> limits to *that*.

Yes, in the next version, I will separate pagetable only from the
rest, for the limits.

> Beyond that, though, there is nothing special about "the IOMMU
> subsystem". The amount of memory an IOMMU driver needs to allocate for
> itself in order to function is not of interest beyond curiosity, it just
> is what it is; limiting it would only break the IOMMU, and if a user

Agree about the amount of memory IOMMU allocates for itself, but that
should be small, if it is not, we have to at least show where the
memory is used.

> thinks it's "too much", the only actionable thing that might help is to
> physically remove devices from the system. Similar for DMA buffers; it
> might be intriguing to account those, but it's not really an actionable
> metric - in the overwhelming majority of cases you can't simply tell a
> driver to allocate less than what it needs. And that is of course
> assuming if we were to account *all* DMA buffers, since whether they
> happen to have an IOMMU translation or not is irrelevant (we'd have
> already accounted the pagetables as pagetables if so).

DMA mappings should be observable (do not have to be limited). At the
very least, it can help with explaining the kernel memory overhead
anomalies on production systems.

> I bet "the networking subsystem" also consumes significant memory on the

It does, and GPU drivers also may consume a significant amount of memory.

> same kind of big systems where IOMMU pagetables would be of any concern.
> I believe some of the some of the "serious" NICs can easily run up
> hundreds of megabytes if not gigabytes worth of queues, SKB pools, etc.
> - would you propose accounting those too?

Yes. Any kind of kernel memory that is proportional to the workload
should be accountable. Someone is using those resources compared to
the idling system, and that someone should be charged.

Pasha
  

On Wed, Nov 29, 2023 at 02:45:03PM -0500, Pasha Tatashin wrote:

> > same kind of big systems where IOMMU pagetables would be of any concern.
> > I believe some of the some of the "serious" NICs can easily run up
> > hundreds of megabytes if not gigabytes worth of queues, SKB pools, etc.
> > - would you propose accounting those too?
> 
> Yes. Any kind of kernel memory that is proportional to the workload
> should be accountable. Someone is using those resources compared to
> the idling system, and that someone should be charged.

There is a difference between charged and accounted

You should be running around adding GFP_KERNEL_ACCOUNT, yes. I already
did a bunch of that work. Split that out from this series and send it
to the right maintainers.

Adding a counter for allocations and showing in procfs is a very
different question. IMHO that should not be done in micro, the
threshold to add a new counter should be high.

There is definately room for a generic debugging feature to break down
GFP_KERNEL_ACCOUNT by owernship somehow. Maybe it can already be done
with BPF. IDK

Jason
  

On Wed, Nov 29, 2023 at 3:03 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Wed, Nov 29, 2023 at 02:45:03PM -0500, Pasha Tatashin wrote:
>
> > > same kind of big systems where IOMMU pagetables would be of any concern.
> > > I believe some of the some of the "serious" NICs can easily run up
> > > hundreds of megabytes if not gigabytes worth of queues, SKB pools, etc.
> > > - would you propose accounting those too?
> >
> > Yes. Any kind of kernel memory that is proportional to the workload
> > should be accountable. Someone is using those resources compared to
> > the idling system, and that someone should be charged.
>
> There is a difference between charged and accounted
>
> You should be running around adding GFP_KERNEL_ACCOUNT, yes. I already
> did a bunch of that work. Split that out from this series and send it
> to the right maintainers.

I will do that.

>
> Adding a counter for allocations and showing in procfs is a very
> different question. IMHO that should not be done in micro, the
> threshold to add a new counter should be high.

I agree, /proc/meminfo, should not include everything, however overall
network consumption that includes memory allocated by network driver
would be useful to have, may be it should be exported by device
drivers and added to the protocol memory. We already have network
protocol memory consumption in procfs:

# awk '{printf "%-10s %s\n", $1, $4}' /proc/net/protocols | grep  -v '\-1'
protocol   memory
UDPv6      22673
TCPv6      16961

> There is definately room for a generic debugging feature to break down
> GFP_KERNEL_ACCOUNT by owernship somehow. Maybe it can already be done
> with BPF. IDK