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 38493C4332F for ; Tue, 18 Oct 2022 15:52:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230244AbiJRPwz (ORCPT ); Tue, 18 Oct 2022 11:52:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37426 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230087AbiJRPwt (ORCPT ); Tue, 18 Oct 2022 11:52:49 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 14242D57D4 for ; Tue, 18 Oct 2022 08:52:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1666108268; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=BoKkcuxL5NREz5vjMqNcHiKa9FwvH6HgAB/kBFDCW9w=; b=g/rhxnw/2kh8Kge3uMnNDqKfCpfX0B/mmIlKX4MVIpNu+9+/Gfnxw8X9R7bdDG2oj+PV7n aATi+QhrmHe0oT3Jf0r3nnmKpewVt/Nn9VfKfEhmwtcb1bzmRLGo4ajBmt8L7Ufx1/hzj+ 6thlgUrnNwpj8wHPDvSi7FyKlxCprUE= Received: from mail-il1-f199.google.com (mail-il1-f199.google.com [209.85.166.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-261--ydRZS5xOpGbOyGlREN-bA-1; Tue, 18 Oct 2022 11:51:06 -0400 X-MC-Unique: -ydRZS5xOpGbOyGlREN-bA-1 Received: by mail-il1-f199.google.com with SMTP id z4-20020a921a44000000b002f8da436b83so12302514ill.19 for ; Tue, 18 Oct 2022 08:51:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=BoKkcuxL5NREz5vjMqNcHiKa9FwvH6HgAB/kBFDCW9w=; b=sQYoO6zueUBGj9pGQZAJxc6LzxRk3m7sDuafeHOFM/RJClxnNe7qHuRr4Ge4borh0m Y4qUpntYH24I7PAxTb4+B6sn94wqD1zbXm7+NXEbb5hiOla3YSOSGKHg32RBSxWyBiQs mWhQtGhVZ0Zpgl/PKU1RiyZn8kPWRY4+hhkWj039gSdhfsDyy2gCOH0k5eu+Htr617Oq GoKEtTt3fhwl1V+irwR8CUIKBJg7bB7CTQeoXnRo0kJYaj9yIRwKdGFT+7lCwExUxS5D d8yLp4HEjIys1oG9RoIaa7JVxlOLRz7UQ6/iMJAjg1NImHvjM8EZCymykBTb9OLSjiBH p8Zg== X-Gm-Message-State: ACrzQf36C8VeaHbMPxcXHP8X/s6S6oCxjFvfBsEktHB4mWQCpwSynFBh 50i05IlV33BwqOFWELBgGHqiwdEWTed29M1XIXlVC0Lip0SjoQ+QZk6G2e1Ty7wkoKbV7Hm8Fua PFuoZohYSoWdH X-Received: by 2002:a05:6638:1903:b0:363:e824:2193 with SMTP id p3-20020a056638190300b00363e8242193mr2260584jal.40.1666108264898; Tue, 18 Oct 2022 08:51:04 -0700 (PDT) X-Google-Smtp-Source: AMsMyM7rTkkIhDBNg5wS6havwCc+dTDzEUFDvH98GZ+b7II2SM5/9WtuFcl6vpreWjVh7ZL84I5kVw== X-Received: by 2002:a05:6638:1903:b0:363:e824:2193 with SMTP id p3-20020a056638190300b00363e8242193mr2260559jal.40.1666108264633; Tue, 18 Oct 2022 08:51:04 -0700 (PDT) Received: from x1n (bras-base-aurron9127w-grc-46-70-31-27-79.dsl.bell.ca. [70.31.27.79]) by smtp.gmail.com with ESMTPSA id h39-20020a022b27000000b00363c866d646sm1188924jaa.26.2022.10.18.08.51.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Oct 2022 08:51:04 -0700 (PDT) Date: Tue, 18 Oct 2022 11:50:59 -0400 From: Peter Xu To: Oliver Upton Cc: Gavin Shan , kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, catalin.marinas@arm.com, bgardon@google.com, shuah@kernel.org, andrew.jones@linux.dev, will@kernel.org, dmatlack@google.com, pbonzini@redhat.com, zhenyzha@redhat.com, james.morse@arm.com, suzuki.poulose@arm.com, alexandru.elisei@arm.com, seanjc@google.com, shan.gavin@gmail.com Subject: Re: [PATCH v5 3/7] KVM: x86: Allow to use bitmap in ring-based dirty page tracking Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Oct 18, 2022 at 10:38:10AM +0300, Oliver Upton wrote: > If we ever get to the point that we can relax this restriction i think a > flag on the BITMAP_WITH_TABLE cap that says "I don't actually set any > bits in the bitmap" would do. We shouldn't hide the cap entirely, as > that would be ABI breakage for VMMs that expect bitmap+ring. I'd rather drop the cap directly if it's just a boolean that tells us "whether we need bitmap to back rings". Btw when I said "dropping it" I meant "don't return 1 for the cap anymore" - we definitely need to make the cap macro stable as part of kvm API.. But I think I misunderstood the proposal previously, sorry. I assumed we were discussing an internal HAVE_DIRTY_RING_WITH_BITMAP only. I noticed this only after I had a closer look at Gavin's patch. Having a cap exposed sounds always good to me. I'll comment on Gavin's patch directly, thanks. -- Peter Xu