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 lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B5973CD98CF for ; Mon, 15 Jun 2026 14:56:37 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wZ8jo-0003NO-F4; Mon, 15 Jun 2026 10:56:33 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wZ8jn-0003Mz-65 for qemu-arm@nongnu.org; Mon, 15 Jun 2026 10:56:31 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wZ8jk-00083w-WE for qemu-arm@nongnu.org; Mon, 15 Jun 2026 10:56:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1781535385; 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=ztWkk3Xpe+kM9d9WYrvzWIt2WX06LB0jeIufZc3Qy1Q=; b=d+TUxx9fyyPbiYLTMo2ICGnPE5vlpF/kUS39R6GDXlxpx0YCJKblvDAa0JN8qjoc8mlLae b0o+DCX5g4jbr28WR6XPsFKNRfMLdDZoIjl7ZIUO28N1XCVMVIlgb6ZcQz8mGwpBKpVqf9 juP4Cs9mShN5bfv+F9hF6UE8efNEl3Q= Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-515-FLiWU35mNrGRjKZuM7kNvw-1; Mon, 15 Jun 2026 10:56:23 -0400 X-MC-Unique: FLiWU35mNrGRjKZuM7kNvw-1 X-Mimecast-MFC-AGG-ID: FLiWU35mNrGRjKZuM7kNvw_1781535382 Received: by mail-ed1-f69.google.com with SMTP id 4fb4d7f45d1cf-68b5941a81bso4065594a12.1 for ; Mon, 15 Jun 2026 07:56:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781535382; x=1782140182; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=ztWkk3Xpe+kM9d9WYrvzWIt2WX06LB0jeIufZc3Qy1Q=; b=IesonyXixdyGAMi6mHzYc9Wy+z92N0syZ/Rj+W5KUZILHz+CnwMg6skjs4PFBmbngG cIb08dmnb7YVM6N/4lXLNMO+kD9w6Dkvsk0knvtVn5eeex2UONpgGiL+Qe0c6pWt8ohD VmbVjjV7IamWojvPP09cSgusUV2WJzcOt0t0ykIe8HVQs/HUfCzSkIJ0uH461OE/bnJK VXxSZ+GqpHCZOQnkBYAJaf42PN25ibIOcKttOb4ZTsMLLlQs7pMM+dxJK6MRrHAHM7ZW WHpH9lQi0uV3Grm+s+Fj5w7sDoMo6xlzg/Qg+DnMmdEvXkrYBHVhk+rVuaQisff1UR5t nNXQ== X-Forwarded-Encrypted: i=1; AFNElJ8zxj0Xr0jDV9IZfWdC/DAVrwsdw/VsjSVxmQ2VuZbOGlikKdsFrtSTT+yHOOT5Fd6cMABsZPf3xw==@nongnu.org X-Gm-Message-State: AOJu0YywyD61mFoLz7Lid1b1CmqFGXi6Vzv/6EAH+Sxbpxdu/YAybZPQ 9/3y87Nb1icn0D5uA6K20g1i/wV+/nqNzw9iU+65NfGsRy9EQtZwc4CcDN6vnHO+tIDozMXbEZU sWGIe/iuB4YldyEUd5nPTl+bKhCj6mOaAyvJeid2My3r2aseVtlbXCA== X-Gm-Gg: Acq92OEnhAm+CQO9k94JlJgpw9tiLBRJXbu8jFsSF/v8Wg8lXOkwzAf5S1CR7JLYHzT DlmbIf2OxGd0VZpaoa5IBHVJnGf7KgKq9J/i9r6FeuPcsVvdkeYb8hwSQuOK3PfnOOJsBYVOC+W eZ4hQEdoUHdrc4Cw3Jzf0qzErgYvAIoHw/8WtW6GTQ6rSO4cuxrq8+beo5iKCqj0u1WzTZnxHor QWPOUuEHeqPCjA9k3Omwpm+l1NqlX/tBGPnKaNm/X0/7537nCKjwFS71Nlfxhq+Edqm8pIOFPIG yDK96E7/C3kKKG9XSrdaXy/CzKiTlT72/u8IOdrC72gvTBd1/NuUByM5N4q8EPjBDDXa/7RF5NS 5/bXLUwdy+M3GCiWCDsg5RR/Ayyr/1GGcK8njrVIyMzU= X-Received: by 2002:a05:6402:44d7:b0:671:9dec:ba3 with SMTP id 4fb4d7f45d1cf-69369d7b16emr5140882a12.13.1781535382145; Mon, 15 Jun 2026 07:56:22 -0700 (PDT) X-Received: by 2002:a05:6402:44d7:b0:671:9dec:ba3 with SMTP id 4fb4d7f45d1cf-69369d7b16emr5140850a12.13.1781535381579; Mon, 15 Jun 2026 07:56:21 -0700 (PDT) Received: from redhat.com (IGLD-80-230-85-71.inter.net.il. [80.230.85.71]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-693791de4a6sm3546295a12.9.2026.06.15.07.56.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Jun 2026 07:56:21 -0700 (PDT) Date: Mon, 15 Jun 2026 10:56:17 -0400 From: "Michael S. Tsirkin" To: Peter Maydell Cc: Gavin Shan , qemu-arm@nongnu.org, qemu-devel@nongnu.org, peterx@redhat.com, alex@shazbot.org, richard.henderson@linaro.org, berrange@redhat.com, philmd@oss.qualcomm.com, philmd@mailo.com, david@kernel.org, clg@redhat.com, pbonzini@redhat.com, phrdina@redhat.com, jugraham@redhat.com, liugang24219@sangfor.com.cn, dinghui@sangfor.com.cn, shan.gavin@gmail.com Subject: Re: [PATCH v2 1/2] system/memory: Use qemu_ram_{copy, move}() in ram device region accessors Message-ID: <20260615105556-mutt-send-email-mst@kernel.org> References: <20260615100200.266968-1-gshan@redhat.com> <20260615100200.266968-2-gshan@redhat.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: t5NzpjzOLOQ9esQ9oZRMcjPl1Z6NysWzyt9s7ockTlM_1781535382 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-arm@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org Sender: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org On Mon, Jun 15, 2026 at 11:57:09AM +0100, Peter Maydell wrote: > On Mon, 15 Jun 2026 at 11:03, Gavin Shan wrote: > > > > All ram device regions were turned to be indirectly accessible by commit > > 4a2e242bbb ("memory: Don't use memcpy for ram_device regions"). This leads > > to guest hang on attempt to build 'cuda-samples' as reported by Julia. The > > guest is started by the following command lines, with GH100 GPU card passed > > from the host. > > > diff --git a/include/system/memory.h b/include/system/memory.h > > index 1417132f6d..5878727d09 100644 > > --- a/include/system/memory.h > > +++ b/include/system/memory.h > > @@ -2897,6 +2897,8 @@ void address_space_register_map_client(AddressSpace *as, QEMUBH *bh); > > void address_space_unregister_map_client(AddressSpace *as, QEMUBH *bh); > > > > /* Internal functions, part of the implementation of address_space_read. */ > > +void qemu_ram_copy(void *dest, const void *src, size_t n); > > +void qemu_ram_move(void *dest, const void *src, size_t n); > > New function prototypes in include headers need documentation comments. > > In particular for these, it's really important that we clearly say > what semantics we are attempting to provide with them, so that > (a) when we're reviewing or later updating the implementation we > know what we are trying to provide > (b) when we're looking at the callsites we know what the function > is guaranteeing to us and what it is not, and thus whether it's > OK to use it or we need something els. > > > +#if defined(__i386__) || defined(__x86_64__) > > +#define HOST_UNALIGNED_MMIO_OK 1 > > +#else > > +#define HOST_UNALIGNED_MMIO_OK 0 > > +#endif > > We need to do something better than this. We can't > just say "oh, we trust that on x86 this works": it is > neither actually true that the compiler guarantees it sorry guarantee what? > even > on x86, nor is it the case that only x86 can do unaligned > accesses to normal RAM. > > thanks > -- PMM