From patchwork Thu Oct 10 18:23:36 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Sean Christopherson X-Patchwork-Id: 13830779 Received: from mail-pf1-f201.google.com (mail-pf1-f201.google.com [209.85.210.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E2FAB1FEFCC for ; Thu, 10 Oct 2024 18:26:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728584765; cv=none; b=A5UucXGw9aaCzWg+6DRz6z/S2ptDa75bxxWfTrLvecGXnl/7Q7Lhn6DLUIqvFWcK7nuY+0L27eudLYEU8M4D+7oMLv8HiS7A+g50/QnWk1V6wPaYYIcESIizBLloHkch0THA9LYyW56o6V4Zn5QguX7CPDRDdeJ6zXsl2HN6fM0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728584765; c=relaxed/simple; bh=+qwur9UMvfPsT7xhW5+1hFXGI3F0T2CjnbFVAQFEZ9U=; 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b=NEKRC93+659kG0Tvqz+//usAh+3RiYqPuIS6rphgeyLd5kdZ23E9qXZc/sWU03FdEi DnZntP8dz54aXCoFv8kuUnYS/QOymPW4hd3vR+HBZplSfIiqmL+yQINgHJVyat9v45Q2 QTjEOEw8VkWYKq+S5mNWKI3Ygnvb8eY+L5uW06TLWhqGmEzm1wNlUocEUBwNqAg6y0yV E1ECLKFocqU7KyGYB0iG+2sJC9TjiaG6xTHAOOdqr7AZy+ik98C7sMGYjYM00xs7Rw1y D6QUHmP4g7sbESCLX43N38tTe8kW3Mx3+ZVwIAgjZEDjKFQJDbWbhqgn/zKNyXpeVq+W 9mTA== X-Gm-Message-State: AOJu0YxpDBneXfAAFlP799mxlHU89Dasd/DNthSjHYa132gjQj2Bmfyp c55wPql1i18nhg4zhHxpYqvLJ/oYpbk1ceFWuSn9gfU3x11Y+s/q0DrvlMRMmHnUeFS/l6bihak IFA== X-Google-Smtp-Source: AGHT+IHthU1bxxWE76UmRU/cmSB/2b+tJYVulTyd1SGmZGLYBHQFEbukUNmDJAlwNs2CFth+SfvGFADhDCI= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:9d:3983:ac13:c240]) (user=seanjc job=sendgmr) by 2002:a05:6a00:2f51:b0:71e:dd:8f9b with SMTP id d2e1a72fcca58-71e1dbe8750mr6976b3a.5.1728584762866; Thu, 10 Oct 2024 11:26:02 -0700 (PDT) Reply-To: Sean Christopherson Date: Thu, 10 Oct 2024 11:23:36 -0700 In-Reply-To: <20241010182427.1434605-1-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241010182427.1434605-1-seanjc@google.com> X-Mailer: git-send-email 2.47.0.rc1.288.g06298d1525-goog Message-ID: <20241010182427.1434605-35-seanjc@google.com> Subject: [PATCH v13 34/85] KVM: Get writable mapping for __kvm_vcpu_map() only when necessary From: Sean Christopherson To: Paolo Bonzini , Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda , Sean Christopherson Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, " =?utf-8?q?Alex_Benn=C3=A9e?= " , Yan Zhao , David Matlack , David Stevens , Andrew Jones When creating a memory map for read, don't request a writable pfn from the primary MMU. While creating read-only mappings can be theoretically slower, as they don't play nice with fast GUP due to the need to break CoW before mapping the underlying PFN, practically speaking, creating a mapping isn't a super hot path, and getting a writable mapping for reading is weird and confusing. Tested-by: Alex Bennée Signed-off-by: Sean Christopherson --- virt/kvm/kvm_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 080740f65061..b845e9252633 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3122,7 +3122,7 @@ int __kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map, struct kvm_follow_pfn kfp = { .slot = gfn_to_memslot(vcpu->kvm, gfn), .gfn = gfn, - .flags = FOLL_WRITE, + .flags = writable ? FOLL_WRITE : 0, .refcounted_page = &map->pinned_page, .pin = true, };