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 X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B38DC433B4 for ; Fri, 23 Apr 2021 12:13:38 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id B1B2E6144D for ; Fri, 23 Apr 2021 12:13:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B1B2E6144D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:41520 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lZugi-00061q-N7 for qemu-devel@archiver.kernel.org; Fri, 23 Apr 2021 08:13:36 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48074) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZufU-0005I2-Hk for qemu-devel@nongnu.org; Fri, 23 Apr 2021 08:12:21 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:60533) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZufP-0004wL-UQ for qemu-devel@nongnu.org; Fri, 23 Apr 2021 08:12:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619179934; 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=yIngoKB9sKahc5f6LBp4xpw4kNGoHsjRYgZfWKlMdTU=; b=VRDWZHqRXz678mEkNsWPE9VuW2b5jnTH61E/rgeMldlXZrgb14ha3PwU9FmHvQhS34C7sK kEvGfGgdCtszn2ZgCGQ+Hz/ywtOaEp/f9E1bxcqMCzDivC7NqDLhtmp4NsAtSTgEzQ9qog B2bVya39E/5Cnd1fkaqdxQFKNBpGVRw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-69-0IVYn-eKN9WxMZ84Qt0_dA-1; Fri, 23 Apr 2021 08:12:13 -0400 X-MC-Unique: 0IVYn-eKN9WxMZ84Qt0_dA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1DA8CA40C0; Fri, 23 Apr 2021 12:12:12 +0000 (UTC) Received: from blackfin.pond.sub.org (ovpn-114-17.ams2.redhat.com [10.36.114.17]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3E7295C1BB; Fri, 23 Apr 2021 12:11:58 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id B066B113525D; Fri, 23 Apr 2021 14:11:56 +0200 (CEST) From: Markus Armbruster To: David Hildenbrand Subject: Re: [PATCH v6 10/15] hostmem: Wire up RAM_NORESERVE via "reserve" property References: <20210421122624.12292-1-david@redhat.com> <20210421122624.12292-11-david@redhat.com> <87a6ppi77c.fsf@dusky.pond.sub.org> <8848ab6a-b435-3f95-1742-6593dff72351@redhat.com> Date: Fri, 23 Apr 2021 14:11:56 +0200 In-Reply-To: <8848ab6a-b435-3f95-1742-6593dff72351@redhat.com> (David Hildenbrand's message of "Fri, 23 Apr 2021 13:16:37 +0200") Message-ID: <874kfxgpyr.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Marcel Apfelbaum , Eduardo Habkost , "Michael S. Tsirkin" , Richard Henderson , qemu-devel@nongnu.org, Peter Xu , "Dr. David Alan Gilbert" , Greg Kurz , Stefan Hajnoczi , Murilo Opsfelder Araujo , Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Igor Mammedov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" David Hildenbrand writes: > On 23.04.21 13:14, Markus Armbruster wrote: >> David Hildenbrand writes: >> >>> Let's provide a way to control the use of RAM_NORESERVE via memory >>> backends using the "reserve" property which defaults to true (old >>> behavior). >>> >>> Only Linux currently supports clearing the flag (and support is checked at >>> runtime, depending on the setting of "/proc/sys/vm/overcommit_memory"). >>> Windows and other POSIX systems will bail out with "reserve=false". >>> >>> The target use case is virtio-mem, which dynamically exposes memory >>> inside a large, sparse memory area to the VM. This essentially allows >>> avoiding to set "/proc/sys/vm/overcommit_memory == 0") when using >>> virtio-mem and also supporting hugetlbfs in the future. >>> >>> Reviewed-by: Peter Xu >>> Reviewed-by: Eduardo Habkost >>> Cc: Markus Armbruster >>> Cc: Eric Blake >>> Cc: Igor Mammedov >>> Signed-off-by: David Hildenbrand >>> --- >>> backends/hostmem-file.c | 11 ++++++----- >>> backends/hostmem-memfd.c | 1 + >>> backends/hostmem-ram.c | 1 + >>> backends/hostmem.c | 32 ++++++++++++++++++++++++++++++++ >>> include/sysemu/hostmem.h | 2 +- >>> qapi/qom.json | 4 ++++ >>> 6 files changed, 45 insertions(+), 6 deletions(-) >>> >>> diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c >>> index b683da9daf..9d550e53d4 100644 >>> --- a/backends/hostmem-file.c >>> +++ b/backends/hostmem-file.c >>> @@ -40,6 +40,7 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) >>> object_get_typename(OBJECT(backend))); >>> #else >>> HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend); >>> + uint32_t ram_flags; >>> gchar *name; >>> if (!backend->size) { >>> @@ -52,11 +53,11 @@ file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) >>> } >>> name = host_memory_backend_get_name(backend); >>> - memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), >>> - name, >>> - backend->size, fb->align, >>> - (backend->share ? RAM_SHARED : 0) | >>> - (fb->is_pmem ? RAM_PMEM : 0), >>> + ram_flags = backend->share ? RAM_SHARED : 0; >>> + ram_flags |= backend->reserve ? 0 : RAM_NORESERVE; >>> + ram_flags |= fb->is_pmem ? RAM_PMEM : 0; >>> + memory_region_init_ram_from_file(&backend->mr, OBJECT(backend), name, >>> + backend->size, fb->align, ram_flags, >>> fb->mem_path, fb->readonly, errp); >>> g_free(name); >>> #endif >>> diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c >>> index 93b5d1a4cf..f3436b623d 100644 >>> --- a/backends/hostmem-memfd.c >>> +++ b/backends/hostmem-memfd.c >>> @@ -55,6 +55,7 @@ memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) >>> name = host_memory_backend_get_name(backend); >>> ram_flags = backend->share ? RAM_SHARED : 0; >>> + ram_flags |= backend->reserve ? 0 : RAM_NORESERVE; >>> memory_region_init_ram_from_fd(&backend->mr, OBJECT(backend), name, >>> backend->size, ram_flags, fd, 0, errp); >>> g_free(name); >>> diff --git a/backends/hostmem-ram.c b/backends/hostmem-ram.c >>> index 741e701062..b8e55cdbd0 100644 >>> --- a/backends/hostmem-ram.c >>> +++ b/backends/hostmem-ram.c >>> @@ -29,6 +29,7 @@ ram_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) >>> name = host_memory_backend_get_name(backend); >>> ram_flags = backend->share ? RAM_SHARED : 0; >>> + ram_flags |= backend->reserve ? 0 : RAM_NORESERVE; >>> memory_region_init_ram_flags_nomigrate(&backend->mr, OBJECT(backend), name, >>> backend->size, ram_flags, errp); >>> g_free(name); >> >> As the commit message says, @reserve translates to RAM_NORESERVE. >> Good. >> I figure passing RAM_NORESERVE can't make these functions fail. >> Correct? >> @reserve defaults to true. The commit message assures us this gives >> us >> the old behavior. Good. But the patch *adds* flag RAM_NORESERVE when >> it is true. Now I'm confused. > > ram_flags |= backend->reserve ? 0 : RAM_NORESERVE; > > translates to > > if (!backend->reserve) > ram_flags |= RAM_NORESERVE; You're right! /me uncrosses eyes... > I thought for a while if calling the property "noreserve" would be > cleaner, but decided against it. I dislike "negative" flag names, too.