From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21876C61DA4 for ; Wed, 15 Feb 2023 01:17:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233320AbjBOBRH (ORCPT ); Tue, 14 Feb 2023 20:17:07 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36802 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233293AbjBOBRF (ORCPT ); Tue, 14 Feb 2023 20:17:05 -0500 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0928232E47 for ; Tue, 14 Feb 2023 17:16:40 -0800 (PST) Received: by mail-qk1-x74a.google.com with SMTP id o24-20020a05620a22d800b007389d2f57f3so10671208qki.21 for ; Tue, 14 Feb 2023 17:16:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=ZPrYycs38Jm3Sq3undZq9ttXoskj6Xab1yQZ0uAvcW8=; b=nT5UvRV+bdXTY47eDM312ZUnHfNlWrwBJx6pdwuGEIubphNFZSWnMXxcpXFhQpNXYh F8TnEG1zuWzDqzduwqwOrXyGlqCFCkM98iRpeBU1tcpHvFAk4+JIxRxdH+TKZmx8h/lO Bqm9+nSVsOmUHwl0qdzxKY2MrmCICC2ZmEOhcHWcESFpdcAQrCCKl3VAR52ACOxfx1Cl 4HRdc0oHWA+SMUEa7WpQaDAh7TbB/N+cvqRF5mGV8aRafe2Xo6dzwFGqvQm1cPXymb1X hq3qSrSQJEV5pufNUG/jT2SMrTDNz0J9Fi6QrMD2x1izAiSkB53PtmoiGLWVTEPCWm/j mg5g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; 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=ZPrYycs38Jm3Sq3undZq9ttXoskj6Xab1yQZ0uAvcW8=; b=Ox6bSM/jb5yRyvdnrbYl1Rvl+1vDhyNP9pEcvmX1QNR01T+Dk00Zz+8gKWOO6WDVPW JoDDvjfUJifqfNm+nm9wa+mt2xUI1OouItnsOnyET19QhEHo3CiPJqLDTcIff0E0lGgH xXLF/FAHAn+h9aaxwWj+xcviruPD5P4PqgnvCDV5rCvp1+eQHFpeKd6+VJFsiCALiXVj s1hQIVHzCJbBPDQ1GTy2tOjKvjHzExryuMNsCWF5qcG1PNf5MTkduuQO+gbf6Bsqp9Lq LmQSIVD1jQ/69Wwh9cdi3AXF2PFPWuVlTDOIPSXAvqbO7rDwcN1MDsnudylprpvZEm6c 4JWg== X-Gm-Message-State: AO0yUKUi9VemD4yLaQ3IGHt9JR7tkHaSztmsX78eRD4TmWqqTd84zhrL 0BA/kH/szFPimqQ/gPh/DEJYMqBI59RCCg== X-Google-Smtp-Source: AK7set8OIyhmpWoTab6NgRcquwz3ebP9gVLRLX3gqnZH2lhB8uDvbbDq1XcJNQVsOeixNwKTxn++WoFJjfzvCQ== X-Received: from laogai.c.googlers.com ([fda3:e722:ac3:cc00:2b:7d90:c0a8:2c9]) (user=amoorthy job=sendgmr) by 2002:ac8:498d:0:b0:3b7:fda5:14ba with SMTP id f13-20020ac8498d000000b003b7fda514bamr9963qtq.12.1676423794603; Tue, 14 Feb 2023 17:16:34 -0800 (PST) Date: Wed, 15 Feb 2023 01:16:10 +0000 In-Reply-To: <20230215011614.725983-1-amoorthy@google.com> Mime-Version: 1.0 References: <20230215011614.725983-1-amoorthy@google.com> X-Mailer: git-send-email 2.39.1.581.gbfd45094c4-goog Message-ID: <20230215011614.725983-5-amoorthy@google.com> Subject: [PATCH 4/8] kvm: Allow hva_pfn_fast to resolve read-only faults. From: Anish Moorthy To: Paolo Bonzini , Marc Zyngier Cc: Oliver Upton , Sean Christopherson , James Houghton , Anish Moorthy , Ben Gardon , David Matlack , Ricardo Koller , Chao Peng , Axel Rasmussen , kvm@vger.kernel.org, kvmarm@lists.linux.dev Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org The upcoming mem_fault_nowait commits will make it so that, when the relevant cap is enabled, hva_to_pfn will return after calling hva_to_pfn_fast without ever attempting to pin memory via hva_to_pfn_slow. hva_to_pfn_fast currently just fails for read-only faults. However, there doesn't seem to be a reason that we can't just try pinning the page without FOLL_WRITE instead of immediately falling back to slow-GUP. This commit implements that behavior. Suggested-by: James Houghton Signed-off-by: Anish Moorthy --- virt/kvm/kvm_main.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index d255964ec331e..dae5f48151032 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. */ @@ -2487,16 +2487,18 @@ static bool hva_to_pfn_fast(unsigned long addr, bool write_fault, bool *writable, kvm_pfn_t *pfn) { struct page *page[1]; + bool found_by_fast_gup = + get_user_page_fast_only( + addr, + /* + * Fast pin a writable pfn only if it is a write fault request + * or the caller allows to map a writable pfn for a read fault + * request. + */ + (write_fault || writable) ? FOLL_WRITE : 0, + page); - /* - * Fast pin a writable pfn only if it is a write fault request - * or the caller allows to map a writable pfn for a read fault - * request. - */ - if (!(write_fault || writable)) - return false; - - if (get_user_page_fast_only(addr, FOLL_WRITE, page)) { + if (found_by_fast_gup) { *pfn = page_to_pfn(page[0]); if (writable) -- 2.39.1.581.gbfd45094c4-goog