From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 72DB61AA1DC; Wed, 20 Nov 2024 15:10:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732115410; cv=none; b=V944xBw3t7ASww0kvqDAOqpiyBcypH5WKYLy0BvnA/8CNCFJ5PGeBH3d2OAg7ESR8ck5hWO6RA55HsxyBVcjDW4dXuAUoMDIwVn8jYsntRXBt3jG895MMIPWXeA0vyJhdRHdRKwK8t6R/oOrkWybQkDSJrjcX1/+qS1na71iAM8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732115410; c=relaxed/simple; bh=cee4bpVCHnOQMsJqKoSGXKnmx0DYKK3uELApQYQdZTI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ETGfhkl7LxiW8ga5t4QLr+XjzLDHrRsowZZRC0HE0lm1pINLjESvpSC8+Wo8dkt81OR1ChOGdsA3LB5qhuoj4uPdtsvlepGZdSJEUrcFKEMr86g+UpVF8HelIURUsKtXsuR5RZ4U+aRahDZrkFv2pBX0GPIlRxstcUCTXZH4TUk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=gtlB5RdY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="gtlB5RdY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E4DAC4CECD; Wed, 20 Nov 2024 15:10:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732115410; bh=cee4bpVCHnOQMsJqKoSGXKnmx0DYKK3uELApQYQdZTI=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=gtlB5RdYLkZbaDBqnPNAlIsTsj41sjCI4jtqrjL9fc3svoMh1MeCpjFQJFoysECQs Ymsbmw+EC4YNeoiSEVsZ8pKfao312FflWzf8y6TBgQv73kByn/UGYuzqR+vzDjK7us dndpAAZrSX4v6ILr9McFq4TDDpExoUzP3j+KhSfkMLRcvJ7kuG44rUAxAvK2FIZwEO lsw3F9XCofFWxm4R0EqZYhQJvdAqaP8PAJC/OQ8FwzV3daSfSzE1iCFqA+gnmj2a2u eo9qRB6HvAGfrqjMATsR3loQ8KgfaQH0OLEdiiA3RVOXZ6hh+R+BS2s0pVb/2/vApa qpRE7AAYHyTKQ== Message-ID: <3366bf89-4544-4b82-83ec-fd89dd009228@kernel.org> Date: Wed, 20 Nov 2024 16:10:04 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v4 2/3] page_pool: fix IOMMU crash when driver has already unbound To: Yunsheng Lin , davem@davemloft.net, kuba@kernel.org, pabeni@redhat.com Cc: liuyonglong@huawei.com, fanghaiqing@huawei.com, zhangkun09@huawei.com, Robin Murphy , Alexander Duyck , IOMMU , Ilias Apalodimas , Eric Dumazet , Simon Horman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20241120103456.396577-1-linyunsheng@huawei.com> <20241120103456.396577-3-linyunsheng@huawei.com> Content-Language: en-US From: Jesper Dangaard Brouer In-Reply-To: <20241120103456.396577-3-linyunsheng@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 20/11/2024 11.34, Yunsheng Lin wrote: > Networking driver with page_pool support may hand over page > still with dma mapping to network stack and try to reuse that > page after network stack is done with it and passes it back > to page_pool to avoid the penalty of dma mapping/unmapping. > With all the caching in the network stack, some pages may be > held in the network stack without returning to the page_pool > soon enough, and with VF disable causing the driver unbound, > the page_pool does not stop the driver from doing it's > unbounding work, instead page_pool uses workqueue to check > if there is some pages coming back from the network stack > periodically, if there is any, it will do the dma unmmapping > related cleanup work. > > As mentioned in [1], attempting DMA unmaps after the driver > has already unbound may leak resources or at worst corrupt > memory. Fundamentally, the page pool code cannot allow DMA > mappings to outlive the driver they belong to. > > Currently it seems there are at least two cases that the page > is not released fast enough causing dma unmmapping done after > driver has already unbound: > 1. ipv4 packet defragmentation timeout: this seems to cause > delay up to 30 secs. > 2. skb_defer_free_flush(): this may cause infinite delay if > there is no triggering for net_rx_action(). > > In order not to call DMA APIs to do DMA unmmapping after driver > has already unbound and stall the unloading of the networking > driver, scan the inflight pages using some MM API to do the DMA > unmmapping for those pages when page_pool_destroy() is called. > > The max time of scanning inflight pages is about 1.3 sec for > system with over 300GB memory as mentioned in [3], which seems > acceptable as the scanning is only done when there are indeed > some inflight pages and is done in the slow path. > > Note, the devmem patchset seems to make the bug harder to fix, > and may make backporting harder too. As there is no actual user > for the devmem and the fixing for devmem is unclear for now, > this patch does not consider fixing the case for devmem yet. > > 1. https://lore.kernel.org/lkml/8067f204-1380-4d37-8ffd-007fc6f26738@kernel.org/T/ > 2. https://github.com/netoptimizer/prototype-kernel > 3. https://lore.kernel.org/all/17a24d69-7bf0-412c-a32a-b25d82bb4159@kernel.org/ > CC: Robin Murphy > CC: Alexander Duyck > CC: IOMMU > Fixes: f71fec47c2df ("page_pool: make sure struct device is stable") > Signed-off-by: Yunsheng Lin > Tested-by: Yonglong Liu > --- > include/net/page_pool/types.h | 6 ++- > net/core/page_pool.c | 95 ++++++++++++++++++++++++++++++----- > 2 files changed, 87 insertions(+), 14 deletions(-) > > diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h > index c022c410abe3..7393fd45bc47 100644 > --- a/include/net/page_pool/types.h > +++ b/include/net/page_pool/types.h > @@ -228,7 +228,11 @@ struct page_pool { > */ > refcount_t user_cnt; > > - u64 destroy_cnt; > + /* Lock to avoid doing dma unmapping concurrently when > + * destroy_cnt > 0. > + */ > + spinlock_t destroy_lock; > + unsigned int destroy_cnt; > > /* Slow/Control-path information follows */ > struct page_pool_params_slow slow; > diff --git a/net/core/page_pool.c b/net/core/page_pool.c > index b3dae671eb26..33a314abbba4 100644 > --- a/net/core/page_pool.c > +++ b/net/core/page_pool.c > @@ -272,9 +272,6 @@ static int page_pool_init(struct page_pool *pool, > /* Driver calling page_pool_create() also call page_pool_destroy() */ > refcount_set(&pool->user_cnt, 1); > > - if (pool->dma_map) > - get_device(pool->p.dev); > - > if (pool->slow.flags & PP_FLAG_ALLOW_UNREADABLE_NETMEM) { > /* We rely on rtnl_lock()ing to make sure netdev_rx_queue > * configuration doesn't change while we're initializing > @@ -312,9 +309,6 @@ static void page_pool_uninit(struct page_pool *pool) > { > ptr_ring_cleanup(&pool->ring, NULL); > > - if (pool->dma_map) > - put_device(pool->p.dev); > - > #ifdef CONFIG_PAGE_POOL_STATS > if (!pool->system) > free_percpu(pool->recycle_stats); > @@ -365,7 +359,7 @@ struct page_pool *page_pool_create(const struct page_pool_params *params) > } > EXPORT_SYMBOL(page_pool_create); > > -static void page_pool_return_page(struct page_pool *pool, netmem_ref netmem); > +static void __page_pool_return_page(struct page_pool *pool, netmem_ref netmem); > > static noinline netmem_ref page_pool_refill_alloc_cache(struct page_pool *pool) > { > @@ -403,7 +397,7 @@ static noinline netmem_ref page_pool_refill_alloc_cache(struct page_pool *pool) > * (2) break out to fallthrough to alloc_pages_node. > * This limit stress on page buddy alloactor. > */ > - page_pool_return_page(pool, netmem); > + __page_pool_return_page(pool, netmem); > alloc_stat_inc(pool, waive); > netmem = 0; > break; > @@ -670,7 +664,7 @@ static __always_inline void __page_pool_release_page_dma(struct page_pool *pool, > * a regular page (that will eventually be returned to the normal > * page-allocator via put_page). > */ > -void page_pool_return_page(struct page_pool *pool, netmem_ref netmem) > +void __page_pool_return_page(struct page_pool *pool, netmem_ref netmem) > { > int count; > bool put; > @@ -697,6 +691,27 @@ void page_pool_return_page(struct page_pool *pool, netmem_ref netmem) > */ > } > > +/* Called from page_pool_put_*() path, need to synchronizated with > + * page_pool_destory() path. > + */ > +static void page_pool_return_page(struct page_pool *pool, netmem_ref netmem) > +{ > + unsigned int destroy_cnt; > + > + rcu_read_lock(); > + > + destroy_cnt = READ_ONCE(pool->destroy_cnt); > + if (unlikely(destroy_cnt)) { > + spin_lock_bh(&pool->destroy_lock); > + __page_pool_return_page(pool, netmem); > + spin_unlock_bh(&pool->destroy_lock); > + } else { > + __page_pool_return_page(pool, netmem); > + } > + > + rcu_read_unlock(); > +} > + > static bool page_pool_recycle_in_ring(struct page_pool *pool, netmem_ref netmem) > { > int ret; > @@ -924,7 +939,7 @@ static netmem_ref page_pool_drain_frag(struct page_pool *pool, > return netmem; > } > > - page_pool_return_page(pool, netmem); > + __page_pool_return_page(pool, netmem); > return 0; > } > > @@ -938,7 +953,7 @@ static void page_pool_free_frag(struct page_pool *pool) > if (!netmem || page_pool_unref_netmem(netmem, drain_count)) > return; > > - page_pool_return_page(pool, netmem); > + __page_pool_return_page(pool, netmem); > } > > netmem_ref page_pool_alloc_frag_netmem(struct page_pool *pool, > @@ -1045,7 +1060,7 @@ static void page_pool_empty_alloc_cache_once(struct page_pool *pool) > static void page_pool_scrub(struct page_pool *pool) > { > page_pool_empty_alloc_cache_once(pool); > - pool->destroy_cnt++; > + WRITE_ONCE(pool->destroy_cnt, pool->destroy_cnt + 1); > > /* No more consumers should exist, but producers could still > * be in-flight. > @@ -1119,6 +1134,58 @@ void page_pool_disable_direct_recycling(struct page_pool *pool) > } > EXPORT_SYMBOL(page_pool_disable_direct_recycling); > > +static void page_pool_inflight_unmap(struct page_pool *pool) > +{ > + unsigned int unmapped = 0; > + struct zone *zone; > + int inflight; > + > + if (!pool->dma_map || pool->mp_priv) > + return; > + > + get_online_mems(); > + spin_lock_bh(&pool->destroy_lock); > + > + inflight = page_pool_inflight(pool, false); > + for_each_populated_zone(zone) { > + unsigned long end_pfn = zone_end_pfn(zone); > + unsigned long pfn; > + > + for (pfn = zone->zone_start_pfn; pfn < end_pfn; pfn++) { > + struct page *page = pfn_to_online_page(pfn); > + > + if (!page || !page_count(page) || > + (page->pp_magic & ~0x3UL) != PP_SIGNATURE || > + page->pp != pool) > + continue; > + > + dma_unmap_page_attrs(pool->p.dev, > + page_pool_get_dma_addr(page), > + PAGE_SIZE << pool->p.order, > + pool->p.dma_dir, > + DMA_ATTR_SKIP_CPU_SYNC | > + DMA_ATTR_WEAK_ORDERING); > + page_pool_set_dma_addr(page, 0); > + I feel this belongs in a helper function call. Previously we had a function called: page_pool_release_page(). This was used to convert the page into a normal page again, releasing page_pool dependencies. It was used when packet transitioned into the netstack, but it was removed when we decided it was safe to let netstack return pp pages. Removed in commits: - 535b9c61bdef ("net: page_pool: hide page_pool_release_page()") - 07e0c7d3179d ("net: page_pool: merge page_pool_release_page() with page_pool_return_page()") > + unmapped++; > + > + /* Skip scanning all pages when debug is disabled */ > + if (!IS_ENABLED(CONFIG_DEBUG_NET) && > + inflight == unmapped) > + goto out; > + } > + } > + > +out: > + WARN_ONCE(page_pool_inflight(pool, false) != unmapped, > + "page_pool(%u): unmapped(%u) != inflight pages(%d)\n", > + pool->user.id, unmapped, inflight); > + > + pool->dma_map = false; > + spin_unlock_bh(&pool->destroy_lock); > + put_online_mems(); > +} > + > void page_pool_destroy(struct page_pool *pool) > { > if (!pool) > @@ -1139,6 +1206,8 @@ void page_pool_destroy(struct page_pool *pool) > */ > synchronize_rcu(); > > + page_pool_inflight_unmap(pool); > + Reaching here means we have detected in-flight packets/pages. In "page_pool_inflight_unmap" we scan and find those in-flight pages to DMA unmap them. Then below we wait for these in-flight pages again. Why don't we just "release" (page_pool_release_page) those in-flight pages from belonging to the page_pool, when we found them during scanning? If doing so, we can hopefully remove the periodic checking code below. > page_pool_detached(pool); > pool->defer_start = jiffies; > pool->defer_warn = jiffies + DEFER_WARN_INTERVAL; > @@ -1159,7 +1228,7 @@ void page_pool_update_nid(struct page_pool *pool, int new_nid) > /* Flush pool alloc cache, as refill will check NUMA node */ > while (pool->alloc.count) { > netmem = pool->alloc.cache[--pool->alloc.count]; > - page_pool_return_page(pool, netmem); > + __page_pool_return_page(pool, netmem); > } > } > EXPORT_SYMBOL(page_pool_update_nid); Thanks for continuing to work on this :-) --Jesper