Re: QEMU, MCE, unpoison memory address across reboot

[Avi Kivity <avi@redhat.com>]

On 12/27/2010 11:27 PM, 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.
>

True.  We can munmap() the page (extending it to the huge page size in 
effect), and then mmap() it back in.  The kernel should merge the new 
vma with its neighbors.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.