linux-kernel - Re: [PATCH v3 0/2] iommu/iova: Make the rcache depot properly flexible

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Message-ID: <20924c0f-b752-4f58-91ce-21ed3b305481@huawei.com>
Date: Sat, 6 Jan 2024 15:07:21 +0800
From: "zhangzekun (A)" <zhangzekun11@...wei.com>
To: Ethan Zhao <haifeng.zhao@...ux.intel.com>
CC: <joro@...tes.org>, <will@...nel.org>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>, <john.g.garry@...cle.com>,
	<dheerajkumar.srivastava@....com>, <jsnitsel@...hat.com>, Ido Schimmel
	<idosch@...sch.org>, Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH v3 0/2] iommu/iova: Make the rcache depot properly
 flexible



在 2024/1/6 12:21, Ethan Zhao 写道:
>
> On 1/2/2024 3:24 PM, Ido Schimmel wrote:
>> On Thu, Dec 28, 2023 at 02:23:20PM +0200, Ido Schimmel wrote:
>>> On Tue, Sep 12, 2023 at 05:28:04PM +0100, Robin Murphy wrote:
>>>> v2: 
>>>> https://lore.kernel.org/linux-iommu/cover.1692641204.git.robin.murphy@arm.com/
>>>>
>>>> Hi all,
>>>>
>>>> I hope this is good to go now, just fixed the locking (and threw
>>>> lockdep at it to confirm, which of course I should have done to begin
>>>> with...) and picked up tags.
>>> Hi,
>>>
>>> After pulling the v6.7 changes we started seeing the following memory
>>> leaks [1] of 'struct iova_magazine'. I'm not sure how to reproduce it,
>>> which is why I didn't perform bisection. However, looking at the
>>> mentioned code paths, they seem to have been changed in v6.7 as part of
>>> this patchset. I reverted both patches and didn't see any memory leaks
>>> when running a full regression (~10 hours), but I will repeat it to be
>>> sure.
>> FYI, we didn't see the leaks since reverting these two patches whereas
>> before we saw them almost everyday, so I'm quite sure they introduced
>> the leaks.
>
> Seems some magazines were not freed when one CPU is dead (hot 
> unplugged) ?
>
> static void free_cpu_cached_iovas(unsigned int cpu, struct iova_domain 
> *iovad)
> {
>     struct iova_cpu_rcache *cpu_rcache;
>     struct iova_rcache *rcache;
>     unsigned long flags;
>     int i;
>
>     for (i = 0; i < IOVA_RANGE_CACHE_MAX_SIZE; ++i) {
>         rcache = &iovad->rcaches[i];
>         cpu_rcache = per_cpu_ptr(rcache->cpu_rcaches, cpu);
>         spin_lock_irqsave(&cpu_rcache->lock, flags);
>         iova_magazine_free_pfns(cpu_rcache->loaded, iovad);
>
> +     iova_magazine_free(cpu_rcache->loaded);
>
>         iova_magazine_free_pfns(cpu_rcache->prev, iovad);
>
> +     iova_magazine_free(cpu_rcache->prev);
>
>         spin_unlock_irqrestore(&cpu_rcache->lock, flags);
>     }
> }
It seems cpu_rcache->loaded and cpu_rcache->prev will be freed in 
free_iova_rcaches(), and it should not cause memory leak because 
iova_magazine_free() will be called for each possible cpu.
free_cpu_cached_iovas() is used to free cached iovas in magazines.

Thanks,
Zekun