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[90.235.19.70]) by smtp.gmail.com with ESMTPSA id y25-20020a2e9d59000000b002a8c409f1f5sm1987642ljj.110.2023.05.24.02.19.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 May 2023 02:19:28 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 24 May 2023 11:19:26 +0200 To: Thomas Gleixner Cc: Thomas Gleixner , linux-mm@kvack.org, Andrew Morton , Christoph Hellwig , Uladzislau Rezki , Peter Zijlstra , Baoquan He Subject: Re: [patch 1/6] mm/vmalloc: Prevent stale TLBs in fully utilized blocks Message-ID: References: <20230523135902.517032811@linutronix.de> <20230523140002.575854344@linutronix.de> <7301efcf-943a-4732-a0d1-215f1606535a@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7301efcf-943a-4732-a0d1-215f1606535a@lucifer.local> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 1BBDE40009 X-Stat-Signature: m39ttgbxixibszj9xk68ek8o77fktmk1 X-Rspam-User: X-HE-Tag: 1684919970-707972 X-HE-Meta: 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 34aKKGhG Xz8vNl4zquQfGCqJn/yLwjEReAkE0kgQF18g/u/u2OKCtEGBfHVns3uQwHGq7NDP8eaiYwuhAYyp8FR931eMQ+3nKf9I1GvGfBXjojiihmwuKH8p1lE+VcZsglwQnMEl6M/NlM0lCsQO2Q2CWfVUDJEVicicMOowsdJKIb6EzO05fHwbUp8KKjYTCtYbPfd2uiRloyFBmWZTcQi6vlC+/oCDh1j20fXEFr+0NcVh9R9i/RVLZ9SL1jBAUa7yZn3Sn29zE0A6+DhVPYQpRnbiU9fki0OjQQ19nn+mG/uM/527nFQjI0ouspbY0lhSxxzRL1iWDJSecj89EXhFyjoYK2lUvEkXztgi+Wez2erwmcwqKApW77QyOt3Iv9jgAFtEQ8X9k4U/5mfTK4ZkDdkI7N7M1z572MfqYmaoiozpycS+EskxzLcDSEkpbxn5qowbmCZpMlDjL0cLykUM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, May 23, 2023 at 08:18:10PM +0100, Lorenzo Stoakes wrote: > On Tue, May 23, 2023 at 04:02:11PM +0200, Thomas Gleixner wrote: > > _vm_unmap_aliases() is used to ensure that no unflushed TLB entries for a > > page are left in the system. This is required due to the lazy TLB flush > > mechanism in vmalloc. > > > > This is tried to achieve by walking the per CPU free lists, but those do > > not contain fully utilized vmap blocks because they are removed from the > > free list once the blocks free space became zero. > > Oh Lord. > > > > > So the per CPU list iteration does not find the block and if the page was > > mapped via such a block and the TLB has not yet been flushed, the guarantee > > of _vm_unmap_aliases() that there are no stale TLBs after returning is > > broken: > > > > x = vb_alloc() // Removes vmap_block from free list because vb->free became 0 > > vb_free(x) // Unmaps page and marks in dirty_min/max range > > > > // Page is reused > > vm_unmap_aliases() // Can't find vmap block with the dirty space -> FAIL > > > > So instead of walking the per CPU free lists, walk the per CPU xarrays > > which hold pointers to _all_ active blocks in the system including those > > removed from the free lists. > > > > Signed-off-by: Thomas Gleixner > > --- > > mm/vmalloc.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -2236,9 +2236,10 @@ static void _vm_unmap_aliases(unsigned l > > for_each_possible_cpu(cpu) { > > struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, cpu); > > struct vmap_block *vb; > > + unsigned long idx; > > > > rcu_read_lock(); > > - list_for_each_entry_rcu(vb, &vbq->free, free_list) { > > + xa_for_each(&vbq->vmap_blocks, idx, vb) { > > spin_lock(&vb->lock); > > if (vb->dirty && vb->dirty != VMAP_BBMAP_BITS) { > > unsigned long va_start = vb->va->va_start; > > > > > > LGTM. > > Reviewed-by: Lorenzo Stoakes Reviewed-by: Uladzislau Rezki (Sony)