Messages in this thread |  | | Subject | Re: [PATCH 0/2] KVM: MMU: support VMAs that got remap_pfn_range-ed | From | Xiao Guangrong <> | Date | Mon, 4 Jul 2016 16:21:39 +0800 |
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On 07/04/2016 04:14 PM, Paolo Bonzini wrote: > > > On 04/07/2016 09:59, Xiao Guangrong wrote: >> >>> But apart from this, it's much more obvious to consider the refcount. >>> The x86 MMU code doesn't care if the page is reserved or not; >>> mmu_set_spte does a kvm_release_pfn_clean, hence it makes sense for >>> hva_to_pfn_remapped to try doing a get_page (via kvm_get_pfn) after >>> invoking the fault handler, just like the get_user_pages family of >>> function does. >> >> Well, it's little strange as you always try to get refcont >> for a PFNMAP region without MIXEDMAP which indicates all the memory >> in this region is no 'struct page' backend. > > Fair enough, I can modify the comment. > > /* > * In case the VMA has VM_MIXEDMAP set, whoever called remap_pfn_range > * is also going to call e.g. unmap_mapping_range before the underlying > * non-reserved pages are freed, which will then call our MMU notifier. > * We still have to get a reference here to the page, because the callers > * of *hva_to_pfn* and *gfn_to_pfn* ultimately end up doing a > * kvm_release_pfn_clean on the returned pfn. If the pfn is > * reserved, the kvm_get_pfn/kvm_release_pfn_clean pair will simply > * do nothing. > */ >
Excellent. I like it. :)
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