drivers/iommu/iova.c | 7 +++++++ 1 file changed, 7 insertions(+)
From: Yunfei Wang <yf.wang@mediatek.com>
In alloc_iova_fast function, if __alloc_and_insert_iova_range fail,
alloc_iova_fast will try flushing rcache and retry alloc iova, but
this has an issue:
Since __alloc_and_insert_iova_range fail will set the current alloc
iova size to max32_alloc_size (iovad->max32_alloc_size = size),
when the retry is executed into the __alloc_and_insert_iova_range
function, the retry action will be blocked by the check condition
(size >= iovad->max32_alloc_size) and goto iova32_full directly,
causes the action of retry regular alloc iova in
__alloc_and_insert_iova_range to not actually be executed.
Based on the above, so need reset max32_alloc_size before retry alloc
iova when alloc iova fail, that is set the initial dma_32bit_pfn value
of iovad to max32_alloc_size, so that the action of retry alloc iova
in __alloc_and_insert_iova_range can be executed.
Signed-off-by: Yunfei Wang <yf.wang@mediatek.com>
Cc: <stable@vger.kernel.org> # 5.10.*
---
v2: Cc stable@vger.kernel.org
1. This patch needs to be merged stable branch, add stable@vger.kernel.org
in mail list.
---
drivers/iommu/iova.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
index b28c9435b898..0c085ae8293f 100644
--- a/drivers/iommu/iova.c
+++ b/drivers/iommu/iova.c
@@ -453,6 +453,7 @@ alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
retry:
new_iova = alloc_iova(iovad, size, limit_pfn, true);
if (!new_iova) {
+ unsigned long flags;
unsigned int cpu;
if (!flush_rcache)
@@ -463,6 +464,12 @@ alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
for_each_online_cpu(cpu)
free_cpu_cached_iovas(cpu, iovad);
free_global_cached_iovas(iovad);
+
+ /* Reset max32_alloc_size after flushing rcache for retry */
+ spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
+ iovad->max32_alloc_size = iovad->dma_32bit_pfn;
+ spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
+
goto retry;
}
--
2.18.0On 2022-03-01 01:59, yf.wang--- via iommu wrote:
> From: Yunfei Wang <yf.wang@mediatek.com>
>
> In alloc_iova_fast function, if __alloc_and_insert_iova_range fail,
> alloc_iova_fast will try flushing rcache and retry alloc iova, but
> this has an issue:
>
> Since __alloc_and_insert_iova_range fail will set the current alloc
> iova size to max32_alloc_size (iovad->max32_alloc_size = size),
> when the retry is executed into the __alloc_and_insert_iova_range
> function, the retry action will be blocked by the check condition
> (size >= iovad->max32_alloc_size) and goto iova32_full directly,
> causes the action of retry regular alloc iova in
> __alloc_and_insert_iova_range to not actually be executed.
>
> Based on the above, so need reset max32_alloc_size before retry alloc
> iova when alloc iova fail, that is set the initial dma_32bit_pfn value
> of iovad to max32_alloc_size, so that the action of retry alloc iova
> in __alloc_and_insert_iova_range can be executed.
Have you observed this making any difference in practice?
Given that both free_cpu_cached_iovas() and free_global_cached_iovas()
call iova_magazine_free_pfns(), which calls remove_iova(), which calls
__cached_rbnode_delete_update(), I'm thinking no...
Robin.
> Signed-off-by: Yunfei Wang <yf.wang@mediatek.com>
> Cc: <stable@vger.kernel.org> # 5.10.*
> ---
> v2: Cc stable@vger.kernel.org
> 1. This patch needs to be merged stable branch, add stable@vger.kernel.org
> in mail list.
>
> ---
> drivers/iommu/iova.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index b28c9435b898..0c085ae8293f 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -453,6 +453,7 @@ alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
> retry:
> new_iova = alloc_iova(iovad, size, limit_pfn, true);
> if (!new_iova) {
> + unsigned long flags;
> unsigned int cpu;
>
> if (!flush_rcache)
> @@ -463,6 +464,12 @@ alloc_iova_fast(struct iova_domain *iovad, unsigned long size,
> for_each_online_cpu(cpu)
> free_cpu_cached_iovas(cpu, iovad);
> free_global_cached_iovas(iovad);
> +
> + /* Reset max32_alloc_size after flushing rcache for retry */
> + spin_lock_irqsave(&iovad->iova_rbtree_lock, flags);
> + iovad->max32_alloc_size = iovad->dma_32bit_pfn;
> + spin_unlock_irqrestore(&iovad->iova_rbtree_lock, flags);
> +
> goto retry;
> }
>
>
>
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu
Hi Yunfei,
>> Since __alloc_and_insert_iova_range fail will set the current alloc
>> iova size to max32_alloc_size (iovad->max32_alloc_size = size),
>> when the retry is executed into the __alloc_and_insert_iova_range
>> function, the retry action will be blocked by the check condition
>> (size >= iovad->max32_alloc_size) and goto iova32_full directly,
>> causes the action of retry regular alloc iova in
>> __alloc_and_insert_iova_range to not actually be executed.
>>
>> Based on the above, so need reset max32_alloc_size before retry alloc
>> iova when alloc iova fail, that is set the initial dma_32bit_pfn value
>> of iovad to max32_alloc_size, so that the action of retry alloc iova
>> in __alloc_and_insert_iova_range can be executed.
>
> Have you observed this making any difference in practice?
>
> Given that both free_cpu_cached_iovas() and free_global_cached_iovas()
> call iova_magazine_free_pfns(), which calls remove_iova(), which calls
> __cached_rbnode_delete_update(), I'm thinking no...
>
> Robin.
>
Like Robin pointed out, if some cached iovas are freed by
free_global_cached_iovas()/free_cpu_cached_iovas(),
the max32_alloc_size should be reset to iovad->dma_32bit_pfn.
If no cached iova is freed, resetting max32_alloc_size before
the retry allocation only give us a retry. Is it possible that
other users free their iovas during the additional retry?
alloc_iova_fast()
retry:
alloc_iova() // failed, iovad->max32_alloc_size = size
free_cpu_cached_iovas()
iova_magazine_free_pfns()
remove_iova()
__cached_rbnode_delete_update()
iovad->max32_alloc_size = iovad->dma_32bit_pfn // reset
free_global_cached_iovas()
iova_magazine_free_pfns()
remove_iova()
__cached_rbnode_delete_update()
iovad->max32_alloc_size = iovad->dma_32bit_pfn // reset
goto retry;
thanks,
Miles
On 2022-03-01 23:29, Miles Chen via iommu wrote: > Hi Yunfei, > >>> Since __alloc_and_insert_iova_range fail will set the current alloc >>> iova size to max32_alloc_size (iovad->max32_alloc_size = size), >>> when the retry is executed into the __alloc_and_insert_iova_range >>> function, the retry action will be blocked by the check condition >>> (size >= iovad->max32_alloc_size) and goto iova32_full directly, >>> causes the action of retry regular alloc iova in >>> __alloc_and_insert_iova_range to not actually be executed. >>> >>> Based on the above, so need reset max32_alloc_size before retry alloc >>> iova when alloc iova fail, that is set the initial dma_32bit_pfn value >>> of iovad to max32_alloc_size, so that the action of retry alloc iova >>> in __alloc_and_insert_iova_range can be executed. >> >> Have you observed this making any difference in practice? >> >> Given that both free_cpu_cached_iovas() and free_global_cached_iovas() >> call iova_magazine_free_pfns(), which calls remove_iova(), which calls >> __cached_rbnode_delete_update(), I'm thinking no... >> >> Robin. >> > > Like Robin pointed out, if some cached iovas are freed by > free_global_cached_iovas()/free_cpu_cached_iovas(), > the max32_alloc_size should be reset to iovad->dma_32bit_pfn. > > If no cached iova is freed, resetting max32_alloc_size before > the retry allocation only give us a retry. Is it possible that > other users free their iovas during the additional retry? No, it's not possible, since everyone's serialised by iova_rbtree_lock. If the caches were already empty and the retry gets the lock first, it will still fail again - forcing a reset of max32_alloc_size only means it has to take the slow path to that failure. If another caller *did* manage to get in and free something between free_global_cached_iovas() dropping the lock and alloc_iova() re-taking it, then that would have legitimately reset max32_alloc_size anyway. Thanks, Robin. > alloc_iova_fast() > retry: > alloc_iova() // failed, iovad->max32_alloc_size = size > free_cpu_cached_iovas() > iova_magazine_free_pfns() > remove_iova() > __cached_rbnode_delete_update() > iovad->max32_alloc_size = iovad->dma_32bit_pfn // reset > free_global_cached_iovas() > iova_magazine_free_pfns() > remove_iova() > __cached_rbnode_delete_update() > iovad->max32_alloc_size = iovad->dma_32bit_pfn // reset > goto retry; > > thanks, > Miles > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu
>> If no cached iova is freed, resetting max32_alloc_size before
>> the retry allocation only give us a retry. Is it possible that
>> other users free their iovas during the additional retry?
>
> No, it's not possible, since everyone's serialised by iova_rbtree_lock.
> If the caches were already empty and the retry gets the lock first, it
> will still fail again - forcing a reset of max32_alloc_size only means
> it has to take the slow path to that failure. If another caller *did*
> manage to get in and free something between free_global_cached_iovas()
> dropping the lock and alloc_iova() re-taking it, then that would have
> legitimately reset max32_alloc_size anyway.
Thanks for your explanation.
YF showed me some numbers yesterday and maybe we can have a further
discussion in that test case. (It looks like that some iovas are freed but
their pfn_lo(s) are less than cached_iova->pfn_lo, so max32_alloc_size is not
reset. So there are enought free iovas but the allocation still failed)
__cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free)
{
struct iova *cached_iova;
cached_iova = to_iova(iovad->cached32_node);
if (free == cached_iova ||
(free->pfn_hi < iovad->dma_32bit_pfn &&
free->pfn_lo >= cached_iova->pfn_lo)) {
iovad->cached32_node = rb_next(&free->node);
iovad->max32_alloc_size = iovad->dma_32bit_pfn;
}
...
}
Hi YF,
Could your share your observation of the iova allocation failure you hit?
Thanks,
Miles
From: yf.wang@mediatek.com <yf.wang@medaitek.com>
On Thu, 2022-03-03 at 07:52 +0800, Miles Chen wrote:
> Thanks for your explanation.
>
> YF showed me some numbers yesterday and maybe we can have a further
> discussion in that test case. (It looks like that some iovas are
> freed but
> their pfn_lo(s) are less than cached_iova->pfn_lo, so
> max32_alloc_size is not
> reset. So there are enought free iovas but the allocation still
> failed)
>
> __cached_rbnode_delete_update(struct iova_domain *iovad, struct iova
> *free)
> {
> struct iova *cached_iova;
>
> cached_iova = to_iova(iovad->cached32_node);
> if (free == cached_iova ||
> (free->pfn_hi < iovad->dma_32bit_pfn &&
> free->pfn_lo >= cached_iova->pfn_lo)) {
> iovad->cached32_node = rb_next(&free->node);
> iovad->max32_alloc_size = iovad->dma_32bit_pfn;
> }
> ...
> }
>
> Hi YF,
> Could your share your observation of the iova allocation failure you
> hit?
>
> Thanks,
> Miles
Hi Miles & Robin,
The scenario we encountered in our actual test:
An iova domain with a 3GB iova region (0x4000_0000~0x1_0000_0000),
only alloc iova total size 614788KB), then alloc iova size=0x731f000
fail, and then the retry mechanism is free 300 cache iova at first,
and then retry still fail, the reason for fail is blocked by the
check condition (size >= iovad->max32_alloc_size) and goto iova32_full
directly.
Why is no reset max32_alloc_size in __cached_rbnode_delete_update?
Because of the pfn_lo of the freed cache iova is smaller than the
current cached32_node's pfn_lo (free->pfn_lo < cached_iova->pfn_lo),
so will not execute (iovad->max32_alloc_size = iovad->dma_32bit_pfn),
is blocked by the check condition (free->pfn_lo >= cached_iova-
>pfn_lo).
The issue observed during stress testing, when alloc fail reset
max32_alloc_size to retry can help to allocate iova to those lower
addresses.
The following is the actual stress test log dump:
('pfn_lo', 'size' and 'pfn_hi' has iova_shift in dump log)
size: 0x731f000
max32_alloc_size: 0x731f000
cached_iova: 0xffffff814751a1c0
cached_iova->pfn_lo: 0xf3500000
cached_iova->pfn_hi: 0xf35ff000
1.__alloc_and_insert_iova_range_fail
[name:iova&]__alloc_and_insert_iova_range_fail:
iovad:0xffffff80d5be2808
{granule:0x1000, start_pfn:0x40000, dma_32bit_pfn:0x100000,
max32_alloc_size:0x731f},size:0x731f
2.dump all iova nodes of rbtree, contain cached iova:
[name:iova&]dump_iova_rbtree start, iovad:0xffffff80d5be2808
{rbroot:0xffffff814751a4c0, cached_node:0xffffff80d5be2860,
cached32_node:0xffffff814751a1c0, granule:0x1000, start_pfn:0x40000,
dma_32bit_pfn:0x100000, max32_alloc_size:0x731f}
('pfn_lo', 'size' and 'pfn_hi' has iova_shift in dump log)
[name:iova&]index iova_object pfn_lo size pfn_hi
[name:iova&] 1 0xffffff814751ae00 0x40800000 0x4c9000 0x40cc8000
[name:iova&] 2 0xffffff807c960880 0x40d00000 0xc4000 0x40dc3000
...322 lines of log are omitted here...
[name:iova&]325 0xffffff814751a1c0 0xf3500000 0x100000 0xf35ff000
[name:iova&]326 0xffffff8004552080 0xf3600000 0x100000 0xf36ff000
[name:iova&]327 0xffffff80045524c0 0xf3700000 0xbc000 0xf37bb000
[name:iova&]328 0xffffff814751a700 0xf3800000 0x265000 0xf3a64000
[name:iova&]329 0xffffff8004552180 0xf3c00000 0xa13000 0xf4612000
[name:iova&]330 0xffffff80c1b3eb40 0xf4800000 0xb400000 0xffbff000
[name:iova&]331 0xffffff80d6e0b580 0xffcff000 0x1000 0xffcff000
[name:iova&]332 0xffffff80c8395140 0xffd00000 0x80000 0xffd7f000
[name:iova&]333 0xffffff80c8395000 0xffde0000 0x20000 0xffdff000
[name:iova&]334 0xffffff80c8395380 0xffe00000 0x80000 0xffe7f000
[name:iova&]335 0xffffff80c8395880 0xffec0000 0x20000 0xffedf000
[name:iova&]336 0xffffff80c83957c0 0xffef9000 0x1000 0xffef9000
[name:iova&]337 0xffffff80c83956c0 0xffefa000 0x1000 0xffefa000
[name:iova&]338 0xffffff80c8395f40 0xffefb000 0x1000 0xffefb000
[name:iova&]339 0xffffff80c8395a80 0xffefc000 0x4000 0xffeff000
[name:iova&]340 0xffffff80c1b3e840 0xfff00000 0x100000 0xfffff000
[name:iova&]341 0xffffff80d5be2860 0xfffffffffffff000 0x1000
0xfffffffffffff000
[name:iova&]dump_iova_rbtree done, iovad:0xffffff80d5be2808,
count:341, total_size:625876KB
3.alloc fail, flushing rcache and retry.
[name:iova&]alloc_iova_fast, flushing rcache and retry,
iovad:0xffffff80d5be2808, size:0x731f, limit_pfn:0xfffff
4.retry is executed into the __alloc_and_insert_iova_range function:
[name:iova&]__alloc_and_insert_iova_range fail goto iova32_full,
iovad:0xffffff80d5be2808 {granule:0x1000, start_pfn:0x40000,
dma_32bit_pfn:0x100000, max32_alloc_size:0x731f},size:0x731f
5.dump all iova nodes of rbtree, current caches is already empty:
[name:iova&]dump_iova_rbtree start, iovad:0xffffff80d5be2808
{rbroot:0xffffff80fe76da80, cached_node:0xffffff80d5be2860,
cached32_node:0xffffff814751a1c0, granule:0x1000, start_pfn:0x40000,
dma_32bit_pfn:0x100000, max32_alloc_size:0x731f}
('pfn_lo', 'size' and 'pfn_hi' has iova_shift in dump log)
[name:iova&]index iova_object pfn_lo size pfn_hi
[name:iova&] 1 0xffffff814751ae00 0x40800000 0x4c9000 0x40cc8000
[name:iova&] 2 0xffffff807c960880 0x40d00000 0xc4000 0x40dc3000
[name:iova&] 3 0xffffff81487ce840 0x40e00000 0x37a000 0x41179000
[name:iova&] 4 0xffffff80fe76d600 0x41200000 0x2400000 0x435ff000
[name:iova&] 5 0xffffff8004552000 0x46800000 0x47e2000 0x4afe1000
[name:iova&] 6 0xffffff807c960a40 0x50200000 0x400000 0x505ff000
[name:iova&] 7 0xffffff818cdb5780 0x50600000 0x265000 0x50864000
[name:iova&] 8 0xffffff814751a440 0x50a00000 0x2ae000 0x50cad000
[name:iova&] 9 0xffffff818cdb5d40 0x50e00000 0x4c9000 0x512c8000
[name:iova&] 10 0xffffff81487cef40 0x51400000 0x1a25000 0x52e24000
[name:iova&] 11 0xffffff818cdb5140 0x53c00000 0x400000 0x53fff000
[name:iova&] 12 0xffffff814751a7c0 0x54000000 0x400000 0x543ff000
[name:iova&] 13 0xffffff80fe76d2c0 0x54500000 0xbc000 0x545bb000
[name:iova&] 14 0xffffff81487ce0c0 0x54600000 0x400000 0x549ff000
[name:iova&] 15 0xffffff80fe76d740 0x54a00000 0xbc000 0x54abb000
[name:iova&] 16 0xffffff8004552440 0x54b00000 0xbc000 0x54bbb000
[name:iova&] 17 0xffffff80fe76db80 0x54c00000 0x47e2000 0x593e1000
[name:iova&] 18 0xffffff818cdb5440 0x65000000 0x400000 0x653ff000
[name:iova&] 19 0xffffff8004552880 0x65400000 0x47e2000 0x69be1000
[name:iova&] 20 0xffffff814751acc0 0x6c7e0000 0x20000 0x6c7ff000
[name:iova&] 21 0xffffff80fe76d700 0x6c800000 0x47e2000 0x70fe1000
//0x70fe1000 - 0xebc00000 = 0x7ac1f000:This free range is large enough
[name:iova&] 22 0xffffff80fe76da80 0xebc00000 0x400000 0xebfff000
[name:iova&] 23 0xffffff80045523c0 0xec000000 0x400000 0xec3ff000
[name:iova&] 24 0xffffff8004552780 0xec400000 0x400000 0xec7ff000
[name:iova&] 25 0xffffff814751a1c0 0xf3500000 0x100000 0xf35ff000
[name:iova&] 26 0xffffff8004552080 0xf3600000 0x100000 0xf36ff000
[name:iova&] 27 0xffffff80045524c0 0xf3700000 0xbc000 0xf37bb000
[name:iova&] 28 0xffffff814751a700 0xf3800000 0x265000 0xf3a64000
[name:iova&] 29 0xffffff8004552180 0xf3c00000 0xa13000 0xf4612000
[name:iova&] 30 0xffffff80c1b3eb40 0xf4800000 0xb400000 0xffbff000
[name:iova&] 31 0xffffff80d6e0b580 0xffcff000 0x1000 0xffcff000
[name:iova&] 32 0xffffff80c8395140 0xffd00000 0x80000 0xffd7f000
[name:iova&] 33 0xffffff80c8395000 0xffde0000 0x20000 0xffdff000
[name:iova&] 34 0xffffff80c8395380 0xffe00000 0x80000 0xffe7f000
[name:iova&] 35 0xffffff80c8395880 0xffec0000 0x20000 0xffedf000
[name:iova&] 36 0xffffff80c83957c0 0xffef9000 0x1000 0xffef9000
[name:iova&] 37 0xffffff80c83956c0 0xffefa000 0x1000 0xffefa000
[name:iova&] 38 0xffffff80c8395f40 0xffefb000 0x1000 0xffefb000
[name:iova&] 39 0xffffff80c8395a80 0xffefc000 0x4000 0xffeff000
[name:iova&] 40 0xffffff80c1b3e840 0xfff00000 0x100000 0xfffff000
[name:iova&] 41 0xffffff80d5be2860 0xfffffffffffff000 0x1000
0xfffffffffffff000
[name:iova&]dump_iova_rbtree done, iovad:0xffffff80d5be2808,
count:41, total_size:614788KB
Thanks,
Yunfei.
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