linux-kernel - Re: KVM overflows the stack

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Message-Id: <1216275288.11664.13.camel@nimitz>
Date:	Wed, 16 Jul 2008 23:14:48 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Avi Kivity <avi@...ranet.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	kvm-devel <kvm@...r.kernel.org>,
	"Anthony N. Liguori [imap]" <aliguori@...ibm.com>
Subject: Re: KVM overflows the stack

On Thu, 2008-07-17 at 08:52 +0300, Avi Kivity wrote:
> Dave Hansen wrote:
> > Avi, how would you like this fixed?  I'd be happy to prepare some
> > patches.  Do you have a particular approach that you think we should
> > use?  Just make the big objects dynamically allocated?
> >   
> 
> Yes, things like kvm_lapic_state are way too big to be on the stack.  
> There's an additional problem here, that apparently your gcc (which 
> version?) doesn't fold objects in a switch statement into the same stack 
> slot:

$ gcc -v
gcc version 3.4.6 (Ubuntu 3.4.6-6ubuntu5)

> switch (...) {
>     case x: {
>          struct medium a;
>          ...
>     }
>     case y:
>           struct medium b;
>           ...
>     }
> };
> 
> These could be solved either by stack allocation, or by moving into 
> functions marked noinline.  Whichever is easier.

Did you mean dynamic allocation? :)

-- Dave

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