Messages in this thread | | | Date | Wed, 18 Feb 2015 11:56:14 +0100 | From | Juergen Gross <> | Subject | Re: [Xen-devel] [PATCH 02/13] xen: anchor linear p2m list in shared info structure |
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On 02/18/2015 11:50 AM, Andrew Cooper wrote: > On 18/02/15 10:42, Juergen Gross wrote: >> >>>> /* Set up p2m_top to point to the domain-builder provided p2m >>>> pages */ >>>> @@ -469,8 +473,10 @@ static pte_t *alloc_p2m_pmd(unsigned long addr, >>>> pte_t *pte_pg) >>>> >>>> ptechk = lookup_address(vaddr, &level); >>>> if (ptechk == pte_pg) { >>>> + HYPERVISOR_shared_info->arch.p2m_generation++; >>>> set_pmd(pmdp, >>>> __pmd(__pa(pte_newpg[i]) | _KERNPG_TABLE)); >>>> + HYPERVISOR_shared_info->arch.p2m_generation++; >>> >>> Do these increments of p2m_generation need to be atomic? >> >> Hmm, they are done under lock. I don't think the compiler is allowed to >> reorder the writes to p2m_generation across set_pmd(). > > They do need smp_wmb() to guarantee that the increment is visible before > the update occurs, just as the toolstack will need smp_rmb() to read.
Okay, I'll add smp_wmb() before and after calling set_pmd().
Juergen
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