Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH 2/2] x86/pae: use 64 bit atomic xchg function in native_ptep_get_and_clear | From | Juergen Gross <> | Date | Mon, 20 Aug 2018 10:56:12 +0200 |
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On 20/08/18 10:40, Jan Beulich wrote: >>>> 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.
Uuh, yes.
I'm waiting for more comments, especially regarding the potential need for a paravirt function.
Juergen
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