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 7B240A935 for ; Wed, 12 Apr 2023 21:35:18 +0000 (UTC) Received: by mail-yb1-f202.google.com with SMTP id 186-20020a2510c3000000b00b880000325bso30110929ybq.3 for ; Wed, 12 Apr 2023 14:35:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1681335317; x=1683927317; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=tZP5BD9r0skQIBcVsEuwbsf0/jfPby4JFW+0o25mrlY=; b=DAuQvN09j6rlTcQ+SQvMQ+Srqk6zFEIzLM+R85LsZhahtQ9CqOj17Bl9EwDey3+OVk P61HT30gkple2nno/lQ6MMs2NiUU9yRsMw67CiJ06U4l7n5Y6XMTqmmU4enb4W3pHBmq nBmCLgs5DM0SwjG0Z4HWqplWgT+BrSEOhLpoMD5vE9qPZc9sZNjFbjyUlwuSOybbkUau /NL1HdHJ7Qj+Wnp9YdpsWuGUi7Qwd9lEr+7CEbZOMeleYsWX4yUNsC/N65vWzHpxrdJV Kg9I13GwIJsn6srNEau4xyl+XnBWmGtXj4V9QSu4M9kEdgzLrmgUSFyd/ElRA6N/5V6+ oT/g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681335317; x=1683927317; 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=tZP5BD9r0skQIBcVsEuwbsf0/jfPby4JFW+0o25mrlY=; b=Yd/W2wx1If0js4meU1PjfzJ9NSwv2biII8BgkUOtHLdg1XpXSz0o9R60ST+pH5J2v1 SxqY8sSF7HcEPmCy/uxvRNttLSyKJLnNdIEUzm3k0rrE6LMliuUXb1D9wBwSHZSSu/bK 8FNSHkfBoJkC0wAgi1R1Olh9GAHUJK86wa8LM/wLCqpBabCp2WoRVyCRXWm7/YgUe9Si 1zr+B726x+gdiDNsJDS2hfWnPuEt7cNS+2Gn0macg+ALX5QshnlmlrdChtTd0pdcO8is D60x5MVxWhPQ7cN5iyq3Ki+/WGaqODGGx8EDpNbdoCizKH7GT4Svd2NVm49ISGY932SB /LXQ== X-Gm-Message-State: AAQBX9co0lO2lyBtkBHOCrycKafK1p5CQyelPDRER3cSyx42om2FLGXD +yBfVijl4BmyEUDFKUER1blXW5OiK5g3WQ== X-Google-Smtp-Source: AKy350ad5sOlGC49a3Zq+AqLstAbTPejBd4itxZk6c/jHU4q2Zhim4pjqaakFyBZUvWX5WivnmgBjuGC8os9Ig== X-Received: from laogai.c.googlers.com ([fda3:e722:ac3:cc00:2b:7d90:c0a8:2c9]) (user=amoorthy job=sendgmr) by 2002:a25:d20c:0:b0:b6b:6a39:949c with SMTP id j12-20020a25d20c000000b00b6b6a39949cmr326ybg.6.1681335317547; Wed, 12 Apr 2023 14:35:17 -0700 (PDT) Date: Wed, 12 Apr 2023 21:34:51 +0000 In-Reply-To: <20230412213510.1220557-1-amoorthy@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20230412213510.1220557-1-amoorthy@google.com> X-Mailer: git-send-email 2.40.0.577.gac1e443424-goog Message-ID: <20230412213510.1220557-4-amoorthy@google.com> Subject: [PATCH v3 03/22] KVM: Allow hva_pfn_fast() to resolve read-only faults. From: Anish Moorthy To: pbonzini@redhat.com, maz@kernel.org Cc: oliver.upton@linux.dev, seanjc@google.com, jthoughton@google.com, amoorthy@google.com, bgardon@google.com, dmatlack@google.com, ricarkol@google.com, axelrasmussen@google.com, peterx@redhat.com, kvm@vger.kernel.org, kvmarm@lists.linux.dev 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 f40b72eb0e7bf..cf7d3de6f3689 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2479,7 +2479,7 @@ 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. */ @@ -2493,10 +2493,9 @@ 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) -- 2.40.0.577.gac1e443424-goog