From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38948) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eJLry-0003hn-Sh for qemu-devel@nongnu.org; Mon, 27 Nov 2017 11:02:59 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eJLrt-00033D-1s for qemu-devel@nongnu.org; Mon, 27 Nov 2017 11:02:54 -0500 Date: Mon, 27 Nov 2017 17:02:42 +0100 From: Cornelia Huck Message-ID: <20171127170242.170d01f6.cohuck@redhat.com> In-Reply-To: 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> <20171127120255.2d36c8f3.cohuck@redhat.com> <20171127153436.200a01c7.cohuck@redhat.com> <20171127163055.6c9989cf.cohuck@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: Pierre Morel Cc: Thomas Huth , 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 16:53:04 +0100 Pierre Morel wrote: > On 27/11/2017 16:30, Cornelia Huck wrote: > > On Mon, 27 Nov 2017 16:24:08 +0100 > > Pierre Morel wrote: > > =20 > >> On 27/11/2017 15:34, Cornelia Huck wrote: =20 > >>> On Mon, 27 Nov 2017 12:02:55 +0100 > >>> Cornelia Huck wrote: > >>> =20 > >>>> On Mon, 27 Nov 2017 07:59:36 +0100 > >>>> Thomas Huth wrote: > >>>> =20 > >>>>> On 25.11.2017 14:49, Pierre Morel wrote: =20 > >>>>>> 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 > >>>> =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= handle > >>>>>>>>> two cases. > >>>>>>>>> 1) For pcilg, we need to translate the data to little-endian, t= hus > >>>>>>>>> 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 > >>>>>> > >>>>>> Here is my comprehension of this funny swapping: > >>>>>> > >>>>>> - TCG for a BE guest and a le host swap bytes because if we do (re= gister > >>>>>> & 0x01) in the zPCI interception code it must work what ever the > >>>>>> endianess is. =20 > >>>>> > >>>>> Uhhh, I might have missed that the value has already been byte-swap= ped > >>>>> 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 w= ith > >>>>> bswapXX() instead of le_to_cpuXX()), and if we later wire up zPCI w= ith > >>>>> TCG, we still can fix this if necessary. =20 > >>>> > >>>> I'll try my current pci/tcg patches on LPAR with this (or a v4) on t= op. > >>>> If it works there (it doesn't yet on my laptop), we do have a > >>>> endianness issue... (unfortunately, the reverse isn't true.) =20 > >>> > >>> It does not look too bad: I can get a nice enP1p0s0 device from a > >>> virtio-net-pci with my tcg patches on my laptop (with these patches as > >>> well, of course). So, endianness is likely mostly fine. =20 > >> > >> On the Lpar and on the Laptop or only on the Lpar ? =20 > >=20 > > Both :) =20 >=20 > That's great! :) Btw, lspci says 0001:00:00.0 Ethernet controller: Red Hat, Inc. Virtio network device Subsystem: Red Hat, Inc. Device 0001 Physical Slot: 00000000 Flags: bus master, fast devsel, latency 0 I/O ports at [disabled] [virtual] Memory at 8001000000000000 (32-bit, non-prefetchable) [si= ze=3D4K] Memory at 8002000000000000 (64-bit, prefetchable) [size=3D16K] Expansion ROM at [disabled] [size=3D256K] Capabilities: [98] MSI-X: Enable+ Count=3D3 Masked- Capabilities: [84] Vendor Specific Information: VirtIO: Capabilities: [70] Vendor Specific Information: VirtIO: Notify Capabilities: [60] Vendor Specific Information: VirtIO: DeviceCfg Capabilities: [50] Vendor Specific Information: VirtIO: ISR Capabilities: [40] Vendor Specific Information: VirtIO: CommonCfg Kernel driver in use: virtio-pci Does that look reasonable to you?