kqemu+amd64: fpudna in kernel mode

[Andriy Gapon]

on 11/04/2007 20:07 Jung-uk Kim said the following:
> On Wednesday 11 April 2007 11:22 am, Andriy Gapon wrote:
>> I get swarms of messages "fpudna in kernel mode" in system log when
>> I run qemu with kqemu on FreeBSD 6.2 amd64 host with Windows XP
>> 32-bit guest. I noticed that someone reported this problem a while
>> ago:
>> http://lists.freebsd.org/pipermail/freebsd-emulation/2006-February/
>> 001800.html
> 
> This happens because we do not allow FP instructions in kernel mode as 
> the error message suggested.  Executing FP instructions in kernel 
> mode requires expensive save/restore cycles for FP states.
> 

Jung-uk,

thank you for the reply but there is still something not clear to me.
I've read Bruce's response also, but I must admit I couldn't understand
much.
So, if floating point instructions cause trap then they apparently fail
(or no ?), then why does (k)qemu executes them anyway ? And how (k)qemu
is able to proceed normally after such failure ?


-- 
Andriy Gapon