Messages in this thread | | | Date | Tue, 15 Jun 2010 14:22:06 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH 3/6] KVM: MMU: introduce gfn_to_page_atomic() and gfn_to_pfn_atomic() |
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On 06/15/2010 05:46 AM, Xiao Guangrong wrote: > Introduce gfn_to_page_atomic() and gfn_to_pfn_atomic(), those > functions is fast path and can used in atomic context, the later > patch will use those > > > @@ -942,6 +942,41 @@ unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn) > } > EXPORT_SYMBOL_GPL(gfn_to_hva); > > +static pfn_t hva_to_pfn_atomic(struct kvm *kvm, unsigned long addr) > +{ > + struct page *page[1]; > + int npages; > + pfn_t pfn; > + > + npages = __get_user_pages_fast(addr, 1, 1, page); > + > + if (unlikely(npages != 1)) { > + if (is_hwpoison_address(addr)) { > + get_page(hwpoison_page); > + return page_to_pfn(hwpoison_page); > + } > + get_page(bad_page); > + return page_to_pfn(bad_page); > + } else > + pfn = page_to_pfn(page[0]); > + > + return pfn; > +} >
Too much duplication. How about putting the tail end of the function in a common helper (with an inatomic flag)?
btw, is_hwpoison_address() is racy. While it looks up the address, some other task can unmap the page tables under us.
Andi/Huang?
One way of fixing it is get_user_pages_ptes_fast(), which also returns the pte, also atomically. I want it for other reasons as well (respond to a read fault by gupping the page for read, but allowing write access if the pte indicates it is writeable).
-- error compiling committee.c: too many arguments to function
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