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From: Andrew Jeffery <andrew@aj.id.au>
To: Christian Svensson <blue@cmd.nu>, clg@kaod.org
Cc: Christian Svensson <bluecmd@google.com>,
	"openbmc @ lists . ozlabs . org" <openbmc@lists.ozlabs.org>,
	Joel Stanley <joel@jms.id.au>
Subject: Re: [PATCH] qemu: aspeed_timer: Use signed muldiv for timer resets
Date: Tue, 13 Nov 2018 10:57:43 +1030	[thread overview]
Message-ID: <1542068863.1552891.1574692280.790D270F@webmail.messagingengine.com> (raw)
In-Reply-To: <CADiuDAQ1mjh56ibSd+tNq2NFiJFtLcAfyoC8fdd=y+4Mu+jD6w@mail.gmail.com>

On Tue, 13 Nov 2018, at 05:15, Christian Svensson wrote:
> Hi
> On Mon, Nov 12, 2018 at 7:37 PM Cédric Le Goater <clg@kaod.org> wrote:
> > isn't QEMU using the helpers from :
> >
> >         include/qemu/host-utils.h
> >
> > which do about the same ?
> 
> Multdiv64 only takes unsigned ints, and while I'm not familiar with the
> details of how that propagates to the division, it seems to result in
> nonsensical values for negative inputs.
> Before copying this logic here I looked for an equivalent for signed ints
> but did not find any suitable one, and the expansion seemed simple enough.
> 
> You can see more details in
> https://github.com/openbmc/qemu/issues/14#issuecomment-437692215.

By inspection the concept of the patch seems okay to me. However, the issue
that host-utils.h takes care of in addition to providing helpers is support for
those helpers on systems that don't support 128-bit integers. The patch should
be sent to the upstream lists, and I don't think we should be breaking
qemu-arm-* generally for systems that we might not care about.

Andrew

  reply	other threads:[~2018-11-13  0:27 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-12 14:21 [PATCH] qemu: aspeed_timer: Use signed muldiv for timer resets Christian Svensson
2018-11-12 18:37 ` Cédric Le Goater
2018-11-12 18:45   ` Christian Svensson
2018-11-13  0:27     ` Andrew Jeffery [this message]
2018-11-13  8:58       ` Christian Svensson
2019-01-11 12:30         ` Christian Svensson
2019-01-14  2:14           ` Andrew Jeffery
2019-01-14  7:18             ` Christian Svensson
2019-02-11 22:52               ` Andrew Jeffery

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