Re: [PATCH] kvm tools: Make the whole guest memory mergeable

[Sasha Levin <levinsasha928@gmail.com>]

On Fri, 2011-12-16 at 15:02 +0800, Zang Hongyong wrote:
> 于 2011/12/16,星期五 13:50, Sasha Levin 写道:
> > On Fri, 2011-12-16 at 09:01 +0800, zanghongyong@huawei.com wrote:
> >> If a guest's ram_size exceeds KVM_32BIT_GAP_START, the corresponding kvm tool's
> >> virtual address size should be (ram_size + KVM_32BIT_GAP_SIZE), rather than ram_size.
> > You're right.
> >
> > There are more places than just the madvise() code which make the same
> > error you've spotted (for example, the memslot allocation code), so
> > instead of trying to fix all of them I'd suggest to just update ram_size
> > in kvm__arch_init() before allocating everything - that should fix all
> > of them at once.
> >
> Yes. There are other scenarios with the same error.
> However ram_size sometimes means real guest ram size, and sometimes 
> means virtual address
> size of kvm tool's user space. Shall we define a new variable?

Let's keep it simple. If the user requests more than RAM than
KVM_32BIT_GAP_START just increase it by KVM_32BIT_GAP_SIZE, this way
mapped size == guest size always (we can madvise(MADV_DONTNEED) the gap
in the mmapped ram).

Since a user which requests more than KVM_32BIT_GAP_START will have to
be on 64bit host anyway, there shouldn't be any issue with that.

-- 

Sasha.