From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (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 2BE181C75F for ; Fri, 2 Jun 2023 16:19:50 +0000 (UTC) Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-bacfa4eefd2so3140617276.0 for ; Fri, 02 Jun 2023 09:19:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1685722790; x=1688314790; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=3S/+6B4sIASEmcbAiWUGrwdrzyn3Ij/qOhyq0MCeDZU=; b=3KnMQGCxKmRUQNx9/GCrwoNNuCixk06ds3u4KEOi/wBb8zEVX3zs6I0WB6qefr8Uf5 keKzQ3SMN7tF8SdmDp8m00jbXVEefJ3rH5J+M4XOhW0yOoV7HQc/h92GGhi429v90ErS mt/+ADOIuj/xd+F6GJBmFzwVDCJkIE629FPeaWgIE89Kua6KyLMNJaTLzoqo5hTPnZrj VFEW2lzLBYg8ECwvbQdeD16HEpbsKBAjS8AJeP1FrB75mTCkg5OHvWo9ALaPvZ3337fw 70XglXByk8/ZytgCMJCKNNWPjViqg+pQgBKViEpsXkrw2MroTlNnh2nCzS+nlH0BmF7C HMAw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1685722790; x=1688314790; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=3S/+6B4sIASEmcbAiWUGrwdrzyn3Ij/qOhyq0MCeDZU=; b=gGT14Yc7gZzJujW+3Z/gqYg1UuoaR0DlXQrCj4iaeoaekXMJvj5PhI9Rtb/2GHNzEa GVmsQWzLgn0w/a/sLEqs+p3rdU5Eijim5d11f67Ri3rXkPy86JYZzw/hdLKrsnpsy2Do M4By4llVTr2kI2Sa8PsR4QeRyflB9m5xxySVRd9hUnXpZU8XDH6qBOXR0IxQAsATTAl0 beH0QMOZXVnIKqbtwQYDMsUlXhkfvdNDj0xKuCBLMAEUZm1ycKx6ehxpVVD6JJw1UpUQ xbISKP4xYjyXghTIHn/UJegRN1N+adGZz3QUXTlIUlCJjMTbkcDoOulVX99tlzARkHaS e8Zg== X-Gm-Message-State: AC+VfDxvxnwr/ZSUwCmlSLRaPdAa9gSMlUV1Y7O9kjV0+eAGsyjUwvtQ GXIeS9cKZojoqxvMdrgMC3CWHAz0zJl1wA== X-Google-Smtp-Source: ACHHUZ7LmOAw8I6mCP70UYYxUu8dl4OdoZ+FYLa9vbMmwQKQEEjk5cDjm8BJnNrFHtRHYk8QXcsObPSpVZMJEw== X-Received: from laogai.c.googlers.com ([fda3:e722:ac3:cc00:2b:7d90:c0a8:2c9]) (user=amoorthy job=sendgmr) by 2002:a25:adc6:0:b0:b8f:6b84:33cb with SMTP id d6-20020a25adc6000000b00b8f6b8433cbmr1333210ybe.11.1685722789992; Fri, 02 Jun 2023 09:19:49 -0700 (PDT) Date: Fri, 2 Jun 2023 16:19:06 +0000 In-Reply-To: <20230602161921.208564-1-amoorthy@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20230602161921.208564-1-amoorthy@google.com> X-Mailer: git-send-email 2.41.0.rc0.172.g3f132b7071-goog Message-ID: <20230602161921.208564-2-amoorthy@google.com> Subject: [PATCH v4 01/16] KVM: Allow hva_pfn_fast() to resolve read-only faults. From: Anish Moorthy To: seanjc@google.com, oliver.upton@linux.dev, kvm@vger.kernel.org, kvmarm@lists.linux.dev Cc: pbonzini@redhat.com, maz@kernel.org, robert.hoo.linux@gmail.com, jthoughton@google.com, amoorthy@google.com, bgardon@google.com, dmatlack@google.com, ricarkol@google.com, axelrasmussen@google.com, peterx@redhat.com, nadav.amit@gmail.com, isaku.yamahata@gmail.com Content-Type: text/plain; charset="UTF-8" hva_to_pfn_fast() currently just fails for read-only faults, which is unnecessary. Instead, try pinning the page without passing FOLL_WRITE. This allows read-only faults to (potentially) be resolved without falling back to slow GUP. Suggested-by: James Houghton Signed-off-by: Anish Moorthy --- virt/kvm/kvm_main.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index cb5c13eee193..fd80a560378c 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2482,7 +2482,7 @@ static inline int check_user_page_hwpoison(unsigned long addr) } /* - * The fast path to get the writable pfn which will be stored in @pfn, + * The fast path to get the pfn which will be stored in @pfn, * true indicates success, otherwise false is returned. It's also the * only part that runs if we can in atomic context. */ @@ -2496,10 +2496,9 @@ static bool hva_to_pfn_fast(unsigned long addr, bool write_fault, * or the caller allows to map a writable pfn for a read fault * request. */ - if (!(write_fault || writable)) - return false; + unsigned int gup_flags = (write_fault || writable) ? FOLL_WRITE : 0; - if (get_user_page_fast_only(addr, FOLL_WRITE, page)) { + if (get_user_page_fast_only(addr, gup_flags, page)) { *pfn = page_to_pfn(page[0]); if (writable) -- 2.41.0.rc0.172.g3f132b7071-goog