Re: [Xen-devel] [PATCH] xen/x86: Zero out .bss for PV guests

From: Andrew Cooper
Date: Wed Feb 24 2016 - 09:15:49 EST

On 24/02/16 14:12, David Vrabel wrote:
> On 22/02/16 22:06, Boris Ostrovsky wrote:
>> Baremetal kernels clear .bss early in the boot. Since Xen PV guests don't
>> excecute that early code they should do it too.
>> (Since we introduce macros for specifying 32- and 64-bit registers we
>> can get rid of ifdefs in startup_xen())
> .bss must have been cleared for PV guests otherwise they would be
> horribly broken. What was the method and why is it no longer sufficient?

The domain builder hands out zeroed pages. I don't believe we guarantee
that the guests RAM is clean, but it is in practice.