Re: [PATCH] iommu/iova: Free all CPU rcache for retry when iova alloc failure
From: yf.wang
Date: Fri Mar 04 2022 - 00:06:56 EST
On Fri, 2022-03-04 at 12:46 +0800, yf.wang@xxxxxxxxxxxx wrote:
> From: Yunfei Wang <yf.wang@xxxxxxxxxxxx>
>
> In alloc_iova_fast function, if an iova alloc request fail,
> it will free the iova ranges present in the percpu iova
> rcaches and free global iova rcache and then retry, but
> flushing CPU iova rcaches only for each online CPU, which
> will cause incomplete rcache cleaning, and iova rcaches of
> not online CPU cannot be flushed, because iova rcaches may
> also lead to fragmentation of iova space, so the next retry
> action may still be fail.
>
> Based on the above, so need to flushing all iova rcaches
> for each possible CPU, use for_each_possible_cpu instead of
> for_each_online_cpu like in free_iova_rcaches function,
> so that all rcaches can be completely released to try
> replenishing IOVAs.
>
> Signed-off-by: Yunfei Wang <yf.wang@xxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # 5.4.*
> ---
> drivers/iommu/iova.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c
> index b28c9435b898..5a0637cd7bc2 100644
> --- a/drivers/iommu/iova.c
> +++ b/drivers/iommu/iova.c
> @@ -460,7 +460,7 @@ alloc_iova_fast(struct iova_domain *iovad,
> unsigned long size,
>
> /* Try replenishing IOVAs by flushing rcache. */
> flush_rcache = false;
> - for_each_online_cpu(cpu)
> + for_each_possible_cpu(cpu)
> free_cpu_cached_iovas(cpu, iovad);
> free_global_cached_iovas(iovad);
> goto retry;
The following is the actual stress test log dump:
1. __alloc_and_insert_iova_range_fail
[name:iova&]__alloc_and_insert_iova_range_fail: iovad:0xffffff80dc9e6008 {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:
[name:iova&]index iova pfn_lo size pfn_hi
[name:iova&] 1 0xffffff80680f8f80 0x47000000 0x4c9000 0x474c8000
[name:iova&] 2 0xffffff813e69c140 0x47500000 0x100000 0x475ff000
...317 lines of log are omitted here...
[name:iova&] 319 0xffffff80c8cea540 0xffefc000 0x4000 0xffeff000
[name:iova&] 320 0xffffff80de3a14c0 0xfff00000 0x100000 0xfffff000
[name:iova&] 321 0xffffff80dc9e6060 0xfffffffffffff000 0x1000 0xfffffffffffff000
[name:iova&]dump_iova_rbtree done, iovad:0xffffff80dc9e6008, count:321, total_size:606964KB
3. for_each_possible_cpu dump all cached iovas by iova_magazine pfns:
cpu:*-1: online cpu, cpu:*-0: not online cpu
[name:iova&]dump_iova_list, for_each_possible_cpu iovad:0xffffff80dc9e6008
3.1 online cpu cached iovas:
[name:iova&]dump_cpu_cached_iovas, iovad:0xffffff80dc9e6008, cpu:0-1, cache:0, iova_size:0x1000
[name:iova&]mag iova pfn_lo size pfn_h
[name:iova&]0/2 0xffffff8089c93c40 0xb8aff000 0x1000 0xb8aff000
[name:iova&]1/2 0xffffff8072046c40 0x716cf000 0x1000 0x716cf000
... omit other online cpu cached iovas ...
3.2 not online cpu cached iovas
... omit other not online cpu cached iovas ...
[name:iova&]dump_cpu_cached_iovas, iovad:0xffffff80dc9e6008, cpu:7-0, cache:5, iova_size:0x20000
[name:iova&]mag iova pfn_lo size pfn_hi
[name:iova&]0/10 0xffffff82b728ea40 0xdfbe0000 0x20000 0xdfbff000
[name:iova&]1/10 0xffffff82b728e480 0xee1e0000 0x20000 0xee1ff000
[name:iova&]2/10 0xffffff81a9fc5440 0xf27c0000 0x20000 0xf27df000
[name:iova&]3/10 0xffffff816f213800 0xd7fe0000 0x20000 0xd7fff000
[name:iova&]4/10 0xffffff80aa3fbf00 0xdb0e0000 0x20000 0xdb0ff000
[name:iova&]5/10 0xffffff8109217b00 0x4a7e0000 0x20000 0x4a7ff000
[name:iova&]6/10 0xffffff8109217540 0xb55a0000 0x20000 0xb55bf000
[name:iova&]7/10 0xffffff82b728e580 0xf33c0000 0x20000 0xf33df000
[name:iova&]8/10 0xffffff8109217500 0x7b5e0000 0x20000 0x7b5ff000
[name:iova&]9/10 0xffffff81a9fc5a80 0xf2da0000 0x20000 0xf2dbf000
[name:iova&]dump_iova_list, done iovad:0xffffff80dc9e6008, cpu_mask:0xff(11111111), online_cpu_mask:(00111111)
4. alloc fail, flushing rcache and retry:
[name:iova&]alloc_iova_fast, flushing rcache and retry, iovad:0xffffff80dc9e6008, size:0x731f, limit_pfn:0xfffff
5. retry and alloc fail again.
[name:iova&]__alloc_and_insert_iova_range_fail, iovad:0xffffff80dc9e6008 {granule:0x1000, start_pfn:0x40000, dma_32bit_pfn:0x100000, max32_alloc_size:0x731f},size:0x731f
6. dump all iova nodes of rbtree, contain cached iova:
[name:iova&]dump_iova_rbtree start:
[name:iova&]index iova pfn_lo size pfn_hi
[name:iova&] 1 0xffffff80680f8f80 0x47000000 0x4c9000 0x474c8000
[name:iova&] 2 0xffffff813e69c140 0x47500000 0x100000 0x475ff000
... 215 lines of log are omitted here ...
[name:iova&] 217 0xffffff80c8cea540 0xffefc000 0x4000 0xffeff000
[name:iova&] 218 0xffffff80de3a14c0 0xfff00000 0x100000 0xfffff000
[name:iova&] 219 0xffffff80dc9e6060 0xfffffffffffff000 0x1000 0xfffffffffffff000
[name:iova&]dump_iova_rbtree done, iovad:0xffffff80dc9e6008, count:219, total_size:603640KB
7. for_each_possible_cpu dump all cached iovas by iova_magazine pfns:
cpu:*-1: online cpu, cpu:*-0: not online cpu
[name:iova&]dump_iova_list, for_each_possible_cpu iovad:0xffffff80dc9e6008
7.1 online cpu cached iovas empty
[name:iova&]dump_cpu_cached_iovas, iovad:0xffffff80dc9e6008, cpu:0-1, cache:0, iova_size:0x1000 empty
[name:iova&]dump_cpu_cached_iovas, iovad:0xffffff80dc9e6008, cpu:0-1, cache:1, iova_size:0x2000 empty
... omit other online cpus ...
[name:iova&]dump_cpu_cached_iovas, iovad:0xffffff80dc9e6008, cpu:5-1, cache:4, iova_size:0x10000 empty
[name:iova&]dump_cpu_cached_iovas, iovad:0xffffff80dc9e6008, cpu:5-1, cache:5, iova_size:0x20000 empty
7.1 not online cpu cached iovas still have cached iovas:
... omit other not online cpu cached iovas ...
[name:iova&]dump_cpu_cached_iovas, iovad:0xffffff80dc9e6008, cpu:7-0, cache:5, iova_size:0x20000
[name:iova&]mag iova pfn_lo size pfn_hi
[name:iova&]0/10 0xffffff82b728ea40 0xdfbe0000 0x20000 0xdfbff000
[name:iova&]1/10 0xffffff82b728e480 0xee1e0000 0x20000 0xee1ff000
[name:iova&]2/10 0xffffff81a9fc5440 0xf27c0000 0x20000 0xf27df000
[name:iova&]3/10 0xffffff816f213800 0xd7fe0000 0x20000 0xd7fff000
[name:iova&]4/10 0xffffff80aa3fbf00 0xdb0e0000 0x20000 0xdb0ff000
[name:iova&]5/10 0xffffff8109217b00 0x4a7e0000 0x20000 0x4a7ff000
[name:iova&]6/10 0xffffff8109217540 0xb55a0000 0x20000 0xb55bf000
[name:iova&]7/10 0xffffff82b728e580 0xf33c0000 0x20000 0xf33df000
[name:iova&]8/10 0xffffff8109217500 0x7b5e0000 0x20000 0x7b5ff000
[name:iova&]9/10 0xffffff81a9fc5a80 0xf2da0000 0x20000 0xf2dbf000
[name:iova&]dump_iova_list, done iovad:0xffffff80dc9e6008, cpu_mask:0xff(11111111), online_cpu_mask:0x3f(00111111)
Thanks,
Yunfei.