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[PATCH] paravirt: kpte flush
Create a new PTE function which combines clearing a kernel PTE with the subsequent flush. This allows the two to be easily combined into a single hypercall or paravirt-op. More subtly, reverse the order of the flush for kmap_atomic. Instead of flushing on establishing a mapping, flush on clearing a mapping. This eliminates the possibility of leaving stale kmap entries which may still have valid TLB mappings. This is required for direct mode hypervisors, which need to reprotect all mappings of a given page when changing the page type from a normal page to a protected page (such as a page table or descriptor table page). But it also provides some nicer semantics for real hardware, by providing extra debug-proofing against using stale mappings, as well as ensuring that no stale mappings exist when changing the cacheability attributes of a page, which could lead to cache conflicts when two different types of mappings exist for the same page. Signed-off-by: Zachary Amsden <[email protected]> Cc: Rusty Russell <[email protected]> Cc: Jeremy Fitzhardinge <[email protected]> Cc: Andi Kleen <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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2 changed files with 14 additions and 11 deletions
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@ -441,6 +441,13 @@ extern pte_t *lookup_address(unsigned long address);
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#define pte_unmap_nested(pte) do { } while (0)
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#endif
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/* Clear a kernel PTE and flush it from the TLB */
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#define kpte_clear_flush(ptep, vaddr) \
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do { \
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pte_clear(&init_mm, vaddr, ptep); \
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__flush_tlb_one(vaddr); \
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} while (0)
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/*
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* The i386 doesn't have any external MMU info: the kernel page
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* tables contain all the necessary information.
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