Re: QEMU, MCE, unpoison memory address across reboot

[Huang Ying <ying.huang@intel.com>]

On Tue, 2010-12-28 at 05:27 +0800, Marcelo Tosatti wrote:
> On Sun, Dec 26, 2010 at 02:27:26PM +0200, Avi Kivity wrote:
> > >>  +static void kvm_unpoison_all(void *param)
> > >>  +{
> > >>  +    HWPoisonPage *page, *next_page;
> > >>  +    unsigned long address;
> > >>  +    KVMState *s = param;
> > >>  +
> > >>  +    QLIST_FOREACH_SAFE(page,&hwpoison_page_list, list, next_page) {
> > >>  +        address = (unsigned long)page->vaddr;
> > >>  +        QLIST_REMOVE(page, list);
> > >>  +        kvm_vm_ioctl(s, KVM_UNPOISON_ADDRESS, address);
> > >>  +        qemu_free(page);
> > >>  +    }
> > >>  +}
> > >
> > >Can't you free and reallocate all guest memory instead, on reboot, if
> > >there's a hwpoisoned page? Then you don't need this interface.
> > >
> > 
> > Alternatively, MADV_DONTNEED?  We already use it for ballooning.
> 
> Does not work for hugetlbfs.

Yes.  And I think zap the page range is just the implementation detail
but semantics of MADV_DONTNEED.

But on the other hand, whether qemu_vmalloc is implemented via
posix_memalign on Linux?  If it is, we can not guarantee that
corresponding page table is zapped after qemu_vfree and qemu_vmalloc?
That is glibc implementation details.

Best Regards,
Huang Ying