From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57245) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d1aqe-00050I-Q2 for qemu-devel@nongnu.org; Fri, 21 Apr 2017 11:51:53 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d1aqZ-0007PI-3c for qemu-devel@nongnu.org; Fri, 21 Apr 2017 11:51:52 -0400 Received: from mail-wr0-x243.google.com ([2a00:1450:400c:c0c::243]:36276) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1d1aqY-0007P0-U2 for qemu-devel@nongnu.org; Fri, 21 Apr 2017 11:51:47 -0400 Received: by mail-wr0-x243.google.com with SMTP id v42so4103990wrc.3 for ; Fri, 21 Apr 2017 08:51:46 -0700 (PDT) Sender: Richard Henderson References: <1492631083-23965-1-git-send-email-joserz@linux.vnet.ibm.com> <20170420100301.51a7f10c@t450s.home> <07d71898-c392-c14a-9901-87ad4287bd5d@redhat.com> From: Richard Henderson Message-ID: <06d0870c-2b1e-0c41-63d3-128e642f78c1@twiddle.net> Date: Fri, 21 Apr 2017 08:51:42 -0700 MIME-Version: 1.0 In-Reply-To: <07d71898-c392-c14a-9901-87ad4287bd5d@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 0/2] VFIO: Make 8-byte accesses atomic List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , Alex Williamson Cc: Jose Ricardo Ziviani , qemu-devel@nongnu.org, aik@ozlabs.ru, mdroth@linux.vnet.ibm.com On 04/21/2017 03:06 AM, Paolo Bonzini wrote: > > > On 20/04/2017 18:03, Alex Williamson wrote: >> On Thu, 20 Apr 2017 00:19:23 -0700 >> Richard Henderson wrote: >> >>> On 04/19/2017 12:44 PM, Jose Ricardo Ziviani wrote: >>>> This patchset has two patches: >>>> [1] 8-byte writes to non-mapped MMIO are broken into pairs of 4-byte writes, this patch makes such pairs atomic. >>>> >>>> [2] Enable 8-byte accesses in vfio_region_write and vfio_region_read. >>>> >>>> Patches based on master. >>>> >>>> Jose Ricardo Ziviani (2): >>>> vfio: Set MemoryRegionOps:max_access_size and min_access_size >>>> vfio: enable 8-byte reads/writes to vfio >>>> >>>> hw/vfio/common.c | 14 ++++++++++++++ >>>> 1 file changed, 14 insertions(+) >>>> >>> >>> I think these patches need to be squashed to be bisectable. >> >> No, I think it's fine. The point of patch 1/2 is to indicate that the >> hardware supports 8-byte accesses, which will still be broken into 2 >> 4-byte accesses because we don't yet set the implemented width beyond >> the default. The important part is that the mutex will now group the 4 >> byte access pair together rather than letting them get re-ordered. >> Patch 2/2 then implements native 8-byte access. I appreciate them >> being separate for this subtle nuance, but maybe I'm not seeing the >> same issue as you. Thanks, > ' > I agree, the patches looks fine as is. Sorry, I misread the first patch, thinking that indicating hw support for 8 byte required implementation of 8 byte. r~