From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41906) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eJHBo-0008TF-Uc for qemu-devel@nongnu.org; Mon, 27 Nov 2017 06:03:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eJHBl-0000Rd-3y for qemu-devel@nongnu.org; Mon, 27 Nov 2017 06:03:05 -0500 Date: Mon, 27 Nov 2017 12:02:55 +0100 From: Cornelia Huck Message-ID: <20171127120255.2d36c8f3.cohuck@redhat.com> In-Reply-To: <2ab76ab0-b20a-9eaf-cafb-195e1621edd6@redhat.com> References: <1511388334-16347-1-git-send-email-pmorel@linux.vnet.ibm.com> <1511388334-16347-2-git-send-email-pmorel@linux.vnet.ibm.com> <3acc6fdb-5638-97b2-2dc7-bce34d22cd1f@redhat.com> <20171123104903.24424b40.cohuck@redhat.com> <20171123110844.4649f3b1.cohuck@redhat.com> <58a08c1d-3935-42e7-cdc0-7bc45c08d2d3@redhat.com> <20171123113326.3b2c5281.cohuck@redhat.com> <6ab0d29e-1af0-888a-c932-a0a294ea225d@linux.vnet.ibm.com> <4000596f-d2a0-c32e-7683-7e074e8132e2@linux.vnet.ibm.com> <37aa6eb3-cbdf-39af-2068-7d0e5949e601@linux.vnet.ibm.com> <2ab76ab0-b20a-9eaf-cafb-195e1621edd6@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [qemu-s390x] [PATCH v3 1/7] s390x/pci: factor out endianess conversion List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Thomas Huth Cc: Pierre Morel , Yi Min Zhao , pasic@linux.vnet.ibm.com, qemu-devel@nongnu.org, agraf@suse.de, borntraeger@de.ibm.com, Qemu-s390x list On Mon, 27 Nov 2017 07:59:36 +0100 Thomas Huth wrote: > On 25.11.2017 14:49, Pierre Morel wrote: > > On 24/11/2017 07:19, Yi Min Zhao wrote: =20 > >> > >> > >> =E5=9C=A8 2017/11/23 =E4=B8=8B=E5=8D=888:18, Thomas Huth =E5=86=99=E9= =81=93: =20 > >>> On 23.11.2017 13:07, Yi Min Zhao wrote: =20 > >>>> Another question, does 'cpu' in cpu_to_le**() or le**_to_cpu() mean = the > >>>> host endianess? =20 > >>> Yes, the "cpu" in cpu_to_le or le_to_cpu means the host, indeed. It's > >>> confusing :-/ > >>> =20 > >>>> If the answers to upper two questions are yes, we actually need hand= le > >>>> two cases. > >>>> 1) For pcilg, we need to translate the data to little-endian, thus > >>>> cpu_to_le**(). > >>>> 2) For pcistg, we need to translate the data to host endianess, thus > >>>> le**_to_cpu(). =20 > >>> I think we've got to byte-swap if the host is big endian (s390x), but > >>> not if the host is little endian (x86 with TCG). =20 > >=20 > > Here is my comprehension of this funny swapping: > >=20 > > - TCG for a BE guest and a le host swap bytes because if we do (register > > & 0x01) in the zPCI interception code it must work what ever the > > endianess is. =20 >=20 > Uhhh, I might have missed that the value has already been byte-swapped > once by TCG for env->regs[r1] ... > Now I'm pretty much completely confused ... sorry for the noise if I was > wrong... I think it's best you ignore my comment for now (i.e. go with > bswapXX() instead of le_to_cpuXX()), and if we later wire up zPCI with > TCG, we still can fix this if necessary. I'll try my current pci/tcg patches on LPAR with this (or a v4) on top. If it works there (it doesn't yet on my laptop), we do have a endianness issue... (unfortunately, the reverse isn't true.) I'll post my pci/tcg patches once I get it mostly working (and it does not look like a horror from the crypt anymore).