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AJvYcCUMT4k53GzvY1yMhuc2GrUjUtHsVGEUF7R55qgqEsb5Mq+H27rvnP63uN4GRk0wG+KN6/H1CHVEiMjkA1iXE5r9j0THksF5obQkifOUlQ== X-Gm-Message-State: AOJu0YxwNO04X0QvWn42DUYxjM119J9HPgXCs5vsV7rL2zneTF1PMJPN CgoawnX3KZD59blujFgOO0JAQ+reUKa6yLVG7iWkd6/lHJUtV5ZdMbV7KLwjLrif1TQ5ubiNWf+ b/Q== X-Google-Smtp-Source: AGHT+IEk24C6d/QoiBbCyIExMW7OdPZLjaBEK4ZPTTj/IX3O1NfqjnOFuoealUEhXp84xV+hhBOGjvPTh7s= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:707:b0:dfa:ba40:6f43 with SMTP id 3f1490d57ef6-dfaba407295mr112473276.2.1717460587664; Mon, 03 Jun 2024 17:23:07 -0700 (PDT) Date: Mon, 3 Jun 2024 17:23:06 -0700 In-Reply-To: Mime-Version: 1.0 References: <20240529180510.2295118-3-jthoughton@google.com> Message-ID: Subject: Re: [PATCH v4 2/7] mm: multi-gen LRU: Have secondary MMUs participate in aging From: Sean Christopherson To: James Houghton Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kvm@vger.kernel.org, linux-doc@vger.kernel.org, Catalin Marinas , Atish Patra , linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-kselftest@vger.kernel.org, Raghavendra Rao Ananta , linux-riscv@lists.infradead.org, Shuah Khan , Yu Zhao , Jonathan Corbet , Anup Patel , Huacai Chen , David Rientjes , Zenghui Yu , Axel Rasmussen , linux-mips@vger.kernel.org, Albert Ou , Ryan Roberts , Will Deacon , Suzuki K Poulose , Shaoqin Huang , Nicholas Piggin , Bibo Mao , loongarch@lists.linux.dev, Paul Walmsley , David Matlack , Palmer Dabbelt , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, Ankit Agrawal , Oliver Upton , James Morse , kvm-riscv@lists.infradead.org, Marc Zyngier , Paolo Bonzini , Andrew Morton , Tianrui Zhao , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Jun 03, 2024, James Houghton wrote: > On Mon, Jun 3, 2024 at 4:03=E2=80=AFPM Sean Christopherson wrote: > > But before we do that, I think we need to perform due dilegence (or pro= vide data) > > showing that having KVM take mmu_lock for write in the "fast only" API = provides > > better total behavior. I.e. that the additional accuracy is indeed wor= th the cost. >=20 > That sounds good to me. I'll drop the Kconfig. I'm not really sure > what to do about the self-test, but that's not really all that > important. Enable it only on architectures+setups that are guaranteed to implement the fast-only API? E.g. on x86, it darn well better be active if the TDP MMU i= s enabled. If the test fails because that doesn't hold true, then we _want_ = the failure.