From: Pierre Morel <pmorel@linux.vnet.ibm.com>
To: Cornelia Huck <cohuck@redhat.com>,
Yi Min Zhao <zyimin@linux.vnet.ibm.com>
Cc: qemu-devel@nongnu.org, agraf@suse.de, borntraeger@de.ibm.com,
pasic@linux.vnet.ibm.com
Subject: Re: [Qemu-devel] [PATCH 6/7] s390x/pci: move the memory region write from pcistg
Date: Mon, 13 Nov 2017 10:39:50 +0100 [thread overview]
Message-ID: <8a33e51f-ab4e-bd07-a998-d19897cdd87e@linux.vnet.ibm.com> (raw)
In-Reply-To: <20171110105116.2a470f57.cohuck@redhat.com>
On 10/11/2017 10:51, Cornelia Huck wrote:
> On Fri, 10 Nov 2017 17:40:12 +0800
> Yi Min Zhao <zyimin@linux.vnet.ibm.com> wrote:
>
>> 在 2017/11/10 上午3:23, Cornelia Huck 写道:
>>> On Tue, 7 Nov 2017 18:24:38 +0100
>>> Pierre Morel <pmorel@linux.vnet.ibm.com> wrote:
>>>
>>>> Let's move the memory region write from pcistg into a dedicated
>>>> function.
>>>> This allows us to prepare a later patch searching for subregions
>>>> inside of the memory region.
>>> OK, so here is the memory region write. Do we have any sleeping
>>> endianness bugs in there for when we wire up tcg? I'm not sure how this
>>> plays with the bswaps (see patch 1).
>>>
>>> But maybe I've just gotten lost somewhere.
>> I think there's no error. For PCI bars' MRs, we got the little-endian data
>> that is exactly fit to the byte ordering of pcilg instruction. For PCI
>> config
>> space, the data has been swapped according to the cpu byte ordering.
>
> Host or target cpu?
>
>> So we use zpci_swap_endian() to swap the data back to the little-endian
>> ordering.
>
I do not see where we use the zpci_swap_endian() function in this patch
or in the zpci_write_bar() function.
> That swap is unconditional. If we were running on a little-endian host,
> it would be wrong, wouldn't it?
I think there is no problem here, we do not use the swap function but we
use the memory_region_dispatch_write() to access a subregion of the PCI
device which is defined as DEVICE_LITTLE_ENDIAN
AFAIU The memory access process the endianness correctly.
>
>>>
>>>> Signed-off-by: Pierre Morel <pmorel@linux.vnet.ibm.com>
>>>> Reviewed-by: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
>>>> ---
>>>> hw/s390x/s390-pci-inst.c | 27 +++++++++++++++++----------
>>>> 1 file changed, 17 insertions(+), 10 deletions(-)
>
--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany
next prev parent reply other threads:[~2017-11-13 9:40 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-07 17:24 [Qemu-devel] [PATCH 0/7] s390x/pci: Improve zPCI to cover more cases Pierre Morel
2017-11-07 17:24 ` [Qemu-devel] [PATCH 1/7] s390x/pci: factor out endianess conversion Pierre Morel
2017-11-09 16:38 ` Cornelia Huck
2017-11-09 18:55 ` Philippe Mathieu-Daudé
2017-11-09 19:20 ` Cornelia Huck
2017-11-13 15:36 ` Pierre Morel
2017-11-13 16:38 ` Cornelia Huck
2017-11-13 16:43 ` Pierre Morel
2017-11-13 9:34 ` Pierre Morel
2017-11-13 9:37 ` Pierre Morel
2017-11-07 17:24 ` [Qemu-devel] [PATCH 2/7] s390x/pci: rework PCI STORE Pierre Morel
2017-11-09 16:50 ` Cornelia Huck
2017-11-10 9:22 ` Yi Min Zhao
2017-11-13 9:03 ` Pierre Morel
2017-11-13 11:48 ` Cornelia Huck
2017-11-13 14:40 ` Pierre Morel
2017-11-07 17:24 ` [Qemu-devel] [PATCH 3/7] s390x/pci: rework PCI LOAD Pierre Morel
2017-11-09 16:51 ` Cornelia Huck
2017-11-13 9:07 ` Pierre Morel
2017-11-13 9:44 ` Pierre Morel
2017-11-07 17:24 ` [Qemu-devel] [PATCH 4/7] s390x/pci: rework PCI STORE BLOCK Pierre Morel
2017-11-13 15:23 ` Cornelia Huck
2017-11-13 16:38 ` Pierre Morel
2017-11-13 17:10 ` Cornelia Huck
2017-11-15 10:05 ` Pierre Morel
2017-11-07 17:24 ` [Qemu-devel] [PATCH 5/7] s390x/pci: move the memory region read from pcilg Pierre Morel
2017-11-07 17:24 ` [Qemu-devel] [PATCH 6/7] s390x/pci: move the memory region write from pcistg Pierre Morel
2017-11-09 19:23 ` Cornelia Huck
2017-11-10 9:40 ` Yi Min Zhao
2017-11-10 9:51 ` Cornelia Huck
2017-11-13 9:17 ` Pierre Morel
2017-11-13 9:39 ` Pierre Morel [this message]
2017-11-13 11:54 ` Cornelia Huck
2017-11-13 14:44 ` Pierre Morel
2017-11-07 17:24 ` [Qemu-devel] [PATCH 7/7] s390x/pci: search for subregion inside the BARs Pierre Morel
2017-11-13 16:03 ` Cornelia Huck
2017-11-07 17:31 ` [Qemu-devel] [PATCH 0/7] s390x/pci: Improve zPCI to cover more cases Cornelia Huck
2017-11-07 17:50 ` Christian Borntraeger
2017-11-08 8:46 ` Cornelia Huck
2017-11-13 17:13 ` Cornelia Huck
2017-11-15 10:02 ` Pierre Morel
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