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[PATCH] paravirt: kpte flush

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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 <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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Zachary Amsden 2006-09-30 23:29:35 -07:00 committed by Linus Torvalds
parent 25e4df5bae
commit 23002d88be
2 changed files with 15 additions and 12 deletions
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20
arch/i386/mm/highmem.c
View file

@ -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();
/*
* force other mappings to Oops if they'll try to access
* this pte without first remap it
*/
pte_clear(&init_mm, vaddr, kmap_pte-idx);
__flush_tlb_one(vaddr);
#endif
/*
* 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.
*/
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;
}

7
include/asm-i386/pgtable.h
View file

@ -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.