Re: qemu/kvm memory allocation

[Paolo Bonzini <pbonzini@redhat.com>]

Il 04/07/2014 16:49, Alexei Fedotov ha scritto:
> Hi engineers,
>
> Could anyone direct me where memory allocation [1] for a new virtual
> machine takes place in the code? I want to understand why the memory
> is initialized with zeroes when I call malloc in a virtual machine.

Nowhere in KVM.

Memory allocation happens in userspace, which usually (but not 
necessarily) means QEMU.  Quoting from the wiki page you mentioned:

> The qemu/kvm process runs mostly like a normal Linux program. It
> allocates its memory with normal malloc() or mmap() calls. If a guest is
> going to have 1GB of physical memory, qemu/kvm will effectively do a
> malloc(1<<30), allocating 1GB of host virtual space. However, just like
> a normal program doing a malloc(), there is no actual physical memory
> allocated at the time of the malloc(). It will not be actually allocated
> until the first time it is touched.

Paolo