Commit 1760f1eb authored Dec 07, 2014 by Christian Borntraeger

x86/xen/p2m: Replace ACCESS_ONCE with READ_ONCE

ACCESS_ONCE does not work reliably on non-scalar types. For
example gcc 4.6 and 4.7 might remove the volatile tag for such
accesses during the SRA (scalar replacement of aggregates) step
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145

)

Change the p2m code to replace ACCESS_ONCE with READ_ONCE.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Acked-by: David Vrabel <david.vrabel@citrix.com>

parent da1a288d

arch/x86/xen/p2m.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -554,7 +554,7 @@ static bool alloc_p2m(unsigned long pfn)
	mid_mfn = NULL;		mid_mfn = NULL;
	}		}

	p2m_pfn = pte_pfn(ACCESS_ONCE(*ptep));		p2m_pfn = pte_pfn(READ_ONCE(*ptep));
	if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) \|\|		if (p2m_pfn == PFN_DOWN(__pa(p2m_identity)) \|\|
	p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {		p2m_pfn == PFN_DOWN(__pa(p2m_missing))) {
	/* p2m leaf page is missing */		/* p2m leaf page is missing */