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SubjectRe: [Xen-devel] [PATCH 2/2] x86/pae: use 64 bit atomic xchg function in native_ptep_get_and_clear
>>> On 20.08.18 at 07:14, <jgross@suse.com> wrote:
> @@ -148,14 +150,14 @@ static inline void pud_clear(pud_t *pudp)
> #ifdef CONFIG_SMP
> static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
> {
> - pte_t res;
> + union {
> + pte_t pte;
> + long long val;
> + } res;

Why the union? pte_t already is one, with the pte field being what
you're after ...

> - /* xchg acts as a barrier before the setting of the high bits */
> - res.pte_low = xchg(&ptep->pte_low, 0);
> - res.pte_high = ptep->pte_high;
> - ptep->pte_high = 0;
> + res.val = arch_atomic64_xchg((atomic64_t *)ptep, 0);

... here.

Jan


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