[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] asm/page.h inconsistencies?
On 6 Jan 2006, at 13:29, Jan Beulich wrote: Could anyone explain the non-symmetric implementation of __pte/__pmd/__pud/__pgd compared to pte_val/pmd_val/pud_val/pgd_val onx86-64? On i386, the "... & 1" is consistently used across all of these,but on x86-64 only the __pte/pte_val pair does so. We only ever test '& 1' in pte_val(). In higher-level *_val functions we need not limit the test to bit 0 (because an unused page directory entry is always 0 in Linux) and also we *cannot* limit the test to bit 0 (at least for pmd_val()) because Xen will silently temporarily remove _PAGE_PRESENT from page directory entries as part of the writable-pagetable implementation. It is certainly arguable that the __pgd/__pud/__pmd macros should do the same test as the corresponding *_val function, for symmetry, but neither xen/i386 nor xen/x86_64 is symmetric right now (at least in xen-unstable.hg). -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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