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Re: [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spe
From: |
Marc Hartmayer |
Subject: |
Re: [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spec |
Date: |
Thu, 30 Jul 2020 15:15:06 +0200 |
On Tue, Jul 21, 2020 at 01:48 PM +0100, Stefan Hajnoczi <stefanha@redhat.com>
wrote:
> On Fri, Jul 17, 2020 at 11:29:28AM +0200, Marc Hartmayer wrote:
>> Since virtio existed even before it got standardized, the virtio
>> standard defines the following types of virtio devices:
>>
>> + legacy device (pre-virtio 1.0)
>> + non-legacy or VIRTIO 1.0 device
>> + transitional device (which can act both as legacy and non-legacy)
>>
>> Virtio 1.0 defines the fields of the virtqueues as little endian,
>> while legacy uses guest's native endian [1]. Currently libvhost-user
>> does not handle virtio endianness at all, i.e. it works only if the
>> native endianness matches with whatever is actually needed. That means
>> things break spectacularly on big-endian targets. Let us handle virtio
>> endianness for non-legacy as required by the virtio specification
>> [1]. We will fence non-legacy virtio devices with the upcoming patch.
>>
>> [1]
>> https://docs.oasis-open.org/virtio/virtio/v1.1/cs01/virtio-v1.1-cs01.html#x1-210003
>>
>> Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
>>
>> ---
>> Note: As we don't support legacy virtio devices there is dead code in
>> libvhost-access.h that could be removed. But for the sake of
>> completeness, I left it in the code.
>
> Please remove the dead code. It is unlikely that legacy device support
> will be required in the future and it will just confuse people reading
> the code.
Done.
>
>> ---
>> contrib/libvhost-user/libvhost-access.h | 61 ++++++++++++
>> contrib/libvhost-user/libvhost-user.c | 119 ++++++++++++------------
>> 2 files changed, 121 insertions(+), 59 deletions(-)
>> create mode 100644 contrib/libvhost-user/libvhost-access.h
>>
>> diff --git a/contrib/libvhost-user/libvhost-access.h
>> b/contrib/libvhost-user/libvhost-access.h
>> new file mode 100644
>> index 000000000000..868ba3e7bfb8
>> --- /dev/null
>> +++ b/contrib/libvhost-user/libvhost-access.h
>> @@ -0,0 +1,61 @@
>> +#ifndef LIBVHOST_ACCESS_H
>
> License/copyright header?
With the dead code removed there is no reason for having
libvhost-access.h so I’ve removed it.
--
Kind regards / Beste Grüße
Marc Hartmayer
IBM Deutschland Research & Development GmbH
Vorsitzender des Aufsichtsrats: Gregor Pillen
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294
- [RFC v2 0/3] Enable virtio-fs on s390x, Marc Hartmayer, 2020/07/17
- [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spec, Marc Hartmayer, 2020/07/17
- Re: [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spec, Stefan Hajnoczi, 2020/07/21
- Re: [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spec,
Marc Hartmayer <=
- Re: [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spec, Michael S. Tsirkin, 2020/07/21
- Re: [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spec, Marc Hartmayer, 2020/07/28
- Re: [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spec, Michael S. Tsirkin, 2020/07/29
- Re: [RFC v2 2/3] libvhost-user: handle endianness as mandated by the spec, Marc Hartmayer, 2020/07/29
[RFC v2 3/3] libvhost-user: fence legacy virtio devices, Marc Hartmayer, 2020/07/17
Re: [RFC v2 0/3] Enable virtio-fs on s390x, no-reply, 2020/07/17