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AJvYcCWtv7RDhBYrGpWUyaKepqExj0L573fSxvPv6jDlYagnlUuuuw43AtS4+8bl1iVE43631p9kICe0sBAEC+cP0lVtpmLI4427qIH5 X-Gm-Message-State: AOJu0YzTUFQ5NZkkuhHXjSxO85i4lMGqHSx7K97663U8t7A9lxQgiqA5 xQM6uT0FIVzpre++drTAq7pnt8yF8HHsG0j7c2sep3E4e54ncBZc3glDXFj5D4GV0TSsoThsPs9 w6A== X-Google-Smtp-Source: AGHT+IGx3SrykKCWRo4963j21qgI5u7l1D5l4vFz5cSTor42JO4rQICXW/WPSO9JICYG6TRZvTrpM8pyR8k= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6a02:308:b0:65c:f515:1590 with SMTP id 41be03b00d2f7-6bfdaf2b2f6mr480a12.11.1717019747924; Wed, 29 May 2024 14:55:47 -0700 (PDT) Date: Wed, 29 May 2024 14:55:46 -0700 In-Reply-To: <20240529180510.2295118-5-jthoughton@google.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240529180510.2295118-1-jthoughton@google.com> <20240529180510.2295118-5-jthoughton@google.com> Message-ID: Subject: Re: [PATCH v4 4/7] KVM: Move MMU lock acquisition for test/clear_young to architecture From: Sean Christopherson To: James Houghton Cc: Andrew Morton , Paolo Bonzini , Albert Ou , Ankit Agrawal , Anup Patel , Atish Patra , Axel Rasmussen , Bibo Mao , Catalin Marinas , David Matlack , David Rientjes , Huacai Chen , James Morse , Jonathan Corbet , Marc Zyngier , Michael Ellerman , Nicholas Piggin , Oliver Upton , Palmer Dabbelt , Paul Walmsley , Raghavendra Rao Ananta , Ryan Roberts , Shaoqin Huang , Shuah Khan , Suzuki K Poulose , Tianrui Zhao , Will Deacon , Yu Zhao , Zenghui Yu , kvm-riscv@lists.infradead.org, kvm@vger.kernel.org, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev Content-Type: text/plain; charset="us-ascii" On Wed, May 29, 2024, James Houghton wrote: > For implementation mmu_notifier_{test,clear}_young, the KVM memslot > walker used to take the MMU lock for us. Now make the architectures > take it themselves. Hmm, *forcing* architectures to take mmu_lock is a step backwards. Rather than add all of this churn, what about adding CONFIG_KVM_MMU_NOTIFIER_LOCKLESS, e.g. static __always_inline int kvm_handle_hva_range_no_flush(struct mmu_notifier *mn, unsigned long start, unsigned long end, gfn_handler_t handler) { struct kvm *kvm = mmu_notifier_to_kvm(mn); const struct kvm_mmu_notifier_range range = { .start = start, .end = end, .handler = handler, .on_lock = (void *)kvm_null_fn, .flush_on_ret = false, .may_block = false, .lockless = IS_ENABLED(CONFIG_KVM_MMU_NOTIFIER_LOCKLESS), }; return __kvm_handle_hva_range(kvm, &range).ret; }