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Re: [Qemu-ppc] [PATCH] virtio: move bi-endian target support to a single
From: |
Greg Kurz |
Subject: |
Re: [Qemu-ppc] [PATCH] virtio: move bi-endian target support to a single location |
Date: |
Tue, 31 May 2016 16:10:46 +0200 |
On Tue, 31 May 2016 15:15:21 +0200
Paolo Bonzini <address@hidden> wrote:
> On 31/05/2016 15:10, Greg Kurz wrote:
> >>> > > +#if defined(TARGET_PPC64) || defined(TARGET_ARM)
> >>> > > +#define LEGACY_VIRTIO_IS_BIENDIAN 1
> >>> > > +#endif
> >> >
> >> > These will only be correct if something else includes cpu.h. Instead of
> >> >
> > Unless I missed something, the TARGET_* macros come from the generated
> > config-target.h header, which is in turn included by qemu/osdep.h and
> > thus included by most of the code.
>
> You're right. Problems _could_ happen if virtio-access.h is included in
> a file compiled without -DNEED_CPU_H (i.e. with common-obj-y instead of
> obj-y) but include/exec/poison.h should take care of that.
>
Exactly !
> >> > defining this, you should add
> >> >
> >> > #include "cpu.h"
> >> >
> >> > at the top of include/hw/virtio-access.h and leave the definitions in
> >> > target-*/cpu.h.
> >> >
> > All this bi-endian stuff is really an old-virtio-only thing... it is
> > only to be used by virtio_access_is_big_endian(). The fact that it
> > broke silently with your cleanup series is yet another proof that
> > this workaround is fragile.
>
> It is not fragile actually. cpu.h doesn't exist in common-obj-y, so the
> TARGET_IS_BIENDIAN define can be safely taken from cpu.h.
>
I was referring to the current situation where virtio_access_is_big_endian()
silently lost its ability to support endian changing guests with:
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -22,11 +22,6 @@
#include "qemu/option.h"
-/* FIXME: Remove NEED_CPU_H. */
-#ifdef NEED_CPU_H
-#include "cpu.h"
-#endif /* !defined(NEED_CPU_H) */
-
which then leads to the usual ENOMEM errors in the guest:
[ 8.959600] blk-mq: failed to allocate request map
[ 8.960171] virtio_blk: probe of virtio0 failed with error -12
> Anyway because of poison.h your solution isn't fragile either, so
>
At least, if someone tries to include virtio-access.h in common-obj-y, she
gets a build break.
> Reviewed-by: Paolo Bonzini <address@hidden>
>
> Paolo
>
Thanks !
--
Greg