Re: [Qemu-devel] [PATCH 4/4] linux-user: Fix fadvise64() syscall support for Mips32

[Aleksandar Markovic]

Sure, Peter, I am going to take your hints and address all your concerns in the 
v2 of this series, which is planned to be posted soon.

I appreciate your guidance,
Aleksandar

________________________________________
From: Peter Maydell address@hidden
Sent: Wednesday, October 05, 2016 5:38 AM
To: Aleksandar Markovic
Cc: Aleksandar Markovic; Riku Voipio; QEMU Developers; Laurent Vivier; Miodrag 
Dinic; Aleksandar Rikalo; Petar Jovanovic; Yongbok Kim; Leon Alrae; Aurelien 
Jarno
Subject: Re: [Qemu-devel] [PATCH 4/4] linux-user: Fix fadvise64() syscall 
support for Mips32

On 5 October 2016 at 03:02, Aleksandar Markovic
<address@hidden> wrote:
> Yes, we could replace TARGET_NR_fadvise64 with TARGET_NR_fadvise64_64
> in Mips32 syscall numbers definition list, and expect the same effect.
>  I just prefer to leave original symbols for syscall numbers, as they
> are defined in kernel headers, unless there is a compelling reason not
> to do it.

I see the argument, but the reason would be "you end up reimplementing
fadvise64_64 as a special case for MIPS for fadvise64, which is a chunk
of extra ugly code that really isn't necessary".

> But, there is more. Code that handles TARGET_NR_fadvise64_64 in Qemu
> utilizes host's posix_advise(). It looks to me that this is just
> plain incorrect. It won't work correctly on 32 bit hosts, with
> respect to  arguments of posix_advise() that are 32-bit (while
> 64-bit value is passed to them) Instead, posix_fadvise64() should
> have been used, IMHO.

If this is broken we should fix it rather than just ignoring it for
MIPS, but I don't think it is broken -- we compile QEMU with
-DFILE_OFFSET_BITS=64, so posix_fadvise() always takes 64 bit arguments
even on 32 bit hosts.

thanks
-- PMM