Commit 23002d88 authored by Zachary Amsden's avatar Zachary Amsden Committed by Linus Torvalds
Browse files

[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: default avatarZachary Amsden <zach@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 25e4df5b

arch/i386/mm/highmem.c

+7 −11
Original line number Diff line number Diff line
@@ -38,22 +38,19 @@ void *kmap_atomic(struct page *page, enum km_type type) 


	idx = type + KM_TYPE_NR*smp_processor_id();

	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);

#ifdef CONFIG_DEBUG_HIGHMEM

	if (!pte_none(*(kmap_pte-idx)))

		BUG();

#endif

	set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));

	__flush_tlb_one(vaddr);



	return (void*) vaddr;

}



void kunmap_atomic(void *kvaddr, enum km_type type)

{

#ifdef CONFIG_DEBUG_HIGHMEM

	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;

	enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();



#ifdef CONFIG_DEBUG_HIGHMEM

	if (vaddr >= PAGE_OFFSET && vaddr < (unsigned long)high_memory) {

		dec_preempt_count();

		preempt_check_resched();
@@ -62,14 +59,14 @@ void kunmap_atomic(void *kvaddr, enum km_type type) 


	if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx))

		BUG();



#endif

	/*

	 * force other mappings to Oops if they'll try to access

	 * this pte without first remap it

	 * Force other mappings to Oops if they'll try to access this pte

	 * without first remap it.  Keeping stale mappings around is a bad idea

	 * also, in case the page changes cacheability attributes or becomes

	 * a protected page in a hypervisor.

	 */

	pte_clear(&init_mm, vaddr, kmap_pte-idx);

	__flush_tlb_one(vaddr);

#endif

	kpte_clear_flush(kmap_pte-idx, vaddr);



	dec_preempt_count();

	preempt_check_resched();
@@ -88,7 +85,6 @@ void *kmap_atomic_pfn(unsigned long pfn, enum km_type type) 
	idx = type + KM_TYPE_NR*smp_processor_id();

	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);

	set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));

	__flush_tlb_one(vaddr);



	return (void*) vaddr;

}

include/asm-i386/pgtable.h

+7 −0
Original line number Diff line number Diff line
@@ -441,6 +441,13 @@ extern pte_t *lookup_address(unsigned long address); 
#define pte_unmap_nested(pte) do { } while (0)

#endif



/* Clear a kernel PTE and flush it from the TLB */

#define kpte_clear_flush(ptep, vaddr)					\

do {									\

	pte_clear(&init_mm, vaddr, ptep);				\

	__flush_tlb_one(vaddr);						\

} while (0)



/*

 * The i386 doesn't have any external MMU info: the kernel page

 * tables contain all the necessary information.

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