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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , Simona Vetter , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Christian =?utf-8?B?S8O2bmln?= , "Paul E. McKenney" , Sean Christopherson , Paolo Bonzini , linux-mm@kvack.org, kvm@vger.kernel.org, linux-rt-devel@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/mmu_notifier: Remove non_block_start/end() from notifier invocation Message-ID: <20260811152914.GI544626@ziepe.ca> References: <20260811135537.GC544626@ziepe.ca> <1d669aca4ffee797b9c29215382444a5b23624b3.camel@infradead.org> <20260811142730.GG544626@ziepe.ca> Precedence: bulk X-Mailing-List: linux-rt-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Tue, Aug 11, 2026 at 03:33:18PM +0100, David Woodhouse wrote: > > At the cost of completely destroying the mm shootdown performance with > > 1s RCU grace period waits every mm operation. No thanks. > > I feel like we're not talking about the same things here. > > The KVM patch which this enables does *not* behave as you have > described. Have you looked at it? It does, it calls synchronize_rcu() from kvm_mmu_notifier_invalidate_range_start() - don't do that... > Nobody's suggesting that we force any *other* MMU notifiers to do > anything that they don't do today. Sure, but nobody should implement their own notifiers with such a heavy locking primitive. Jason