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authorJan Beulich <JBeulich@novell.com>2011-08-16 15:07:41 +0100
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2011-08-17 10:26:48 -0400
commitccbcdf7cf1b5f6c6db30d84095b9c6c53043af55 (patch)
treed1c37475f699fcf1ef48f829f379f7cecda357e1
parent30eefc95841ce51c3281876f0b954dd1d3c0bd5f (diff)
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xen/x86: replace order-based range checking of M2P table by linear one
The order-based approach is not only less efficient (requiring a shift and a compare, typical generated code looking like this mov eax, [machine_to_phys_order] mov ecx, eax shr ebx, cl test ebx, ebx jnz ... whereas a direct check requires just a compare, like in cmp ebx, [machine_to_phys_nr] jae ... ), but also slightly dangerous in the 32-on-64 case - the element address calculation can wrap if the next power of two boundary is sufficiently far away from the actual upper limit of the table, and hence can result in user space addresses being accessed (with it being unknown what may actually be mapped there). Additionally, the elimination of the mistaken use of fls() here (should have been __fls()) fixes a latent issue on x86-64 that would trigger if the code was run on a system with memory extending beyond the 44-bit boundary. CC: stable@kernel.org Signed-off-by: Jan Beulich <jbeulich@novell.com> [v1: Based on Jeremy's feedback] Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
-rw-r--r--arch/x86/include/asm/xen/page.h4
-rw-r--r--arch/x86/xen/enlighten.c4
-rw-r--r--arch/x86/xen/mmu.c12
3 files changed, 12 insertions, 8 deletions
diff --git a/arch/x86/include/asm/xen/page.h b/arch/x86/include/asm/xen/page.h
index 64a619d47d3..7ff4669580c 100644
--- a/arch/x86/include/asm/xen/page.h
+++ b/arch/x86/include/asm/xen/page.h
@@ -39,7 +39,7 @@ typedef struct xpaddr {
((unsigned long)((u64)CONFIG_XEN_MAX_DOMAIN_MEMORY * 1024 * 1024 * 1024 / PAGE_SIZE))
extern unsigned long *machine_to_phys_mapping;
-extern unsigned int machine_to_phys_order;
+extern unsigned long machine_to_phys_nr;
extern unsigned long get_phys_to_machine(unsigned long pfn);
extern bool set_phys_to_machine(unsigned long pfn, unsigned long mfn);
@@ -87,7 +87,7 @@ static inline unsigned long mfn_to_pfn(unsigned long mfn)
if (xen_feature(XENFEAT_auto_translated_physmap))
return mfn;
- if (unlikely((mfn >> machine_to_phys_order) != 0)) {
+ if (unlikely(mfn >= machine_to_phys_nr)) {
pfn = ~0;
goto try_override;
}
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 974a528458a..b960429d5b6 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -77,8 +77,8 @@ EXPORT_SYMBOL_GPL(xen_domain_type);
unsigned long *machine_to_phys_mapping = (void *)MACH2PHYS_VIRT_START;
EXPORT_SYMBOL(machine_to_phys_mapping);
-unsigned int machine_to_phys_order;
-EXPORT_SYMBOL(machine_to_phys_order);
+unsigned long machine_to_phys_nr;
+EXPORT_SYMBOL(machine_to_phys_nr);
struct start_info *xen_start_info;
EXPORT_SYMBOL_GPL(xen_start_info);
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index f987bde77c4..24abc1f50dc 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1713,15 +1713,19 @@ static void __init xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
void __init xen_setup_machphys_mapping(void)
{
struct xen_machphys_mapping mapping;
- unsigned long machine_to_phys_nr_ents;
if (HYPERVISOR_memory_op(XENMEM_machphys_mapping, &mapping) == 0) {
machine_to_phys_mapping = (unsigned long *)mapping.v_start;
- machine_to_phys_nr_ents = mapping.max_mfn + 1;
+ machine_to_phys_nr = mapping.max_mfn + 1;
} else {
- machine_to_phys_nr_ents = MACH2PHYS_NR_ENTRIES;
+ machine_to_phys_nr = MACH2PHYS_NR_ENTRIES;
}
- machine_to_phys_order = fls(machine_to_phys_nr_ents - 1);
+#ifdef CONFIG_X86_32
+ if ((machine_to_phys_mapping + machine_to_phys_nr)
+ < machine_to_phys_mapping)
+ machine_to_phys_nr = (unsigned long *)NULL
+ - machine_to_phys_mapping;
+#endif
}
#ifdef CONFIG_X86_64