diff options
| author | Jeremy Fitzhardinge <jeremy@goop.org> | 2008-05-26 23:31:20 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2008-05-27 10:11:37 +0200 |
| commit | cf0923ea295ba08ae656ef04164a43cb6553ba99 (patch) | |
| tree | c5c8ea1a226edcf7a29bec1953f65469a21756e5 | |
| parent | 8006ec3e911f93d702e1d4a4e387e244ab434924 (diff) | |
xen: efficiently support a holey p2m table
When using sparsemem and memory hotplug, the kernel's pseudo-physical
address space can be discontigious. Previously this was dealt with by
having the upper parts of the radix tree stubbed off. Unfortunately,
this is incompatible with save/restore, which requires a complete p2m
table.
The solution is to have a special distinguished all-invalid p2m leaf
page, which we can point all the hole areas at. This allows the tools
to see a complete p2m table, but it only costs a page for all memory
holes.
It also simplifies the code since it removes a few special cases.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| -rw-r--r-- | arch/x86/xen/mmu.c | 18 |
1 files changed, 12 insertions, 6 deletions
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index 644232aa7bf..da7b45b0506 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -57,8 +57,17 @@ #include "mmu.h" #define P2M_ENTRIES_PER_PAGE (PAGE_SIZE / sizeof(unsigned long)) +#define TOP_ENTRIES (MAX_DOMAIN_PAGES / P2M_ENTRIES_PER_PAGE) -static unsigned long *p2m_top[MAX_DOMAIN_PAGES / P2M_ENTRIES_PER_PAGE]; +/* Placeholder for holes in the address space */ +static unsigned long p2m_missing[P2M_ENTRIES_PER_PAGE] + __attribute__((section(".data.page_aligned"))) = + { [ 0 ... P2M_ENTRIES_PER_PAGE-1 ] = ~0UL }; + + /* Array of pointers to pages containing p2m entries */ +static unsigned long *p2m_top[TOP_ENTRIES] + __attribute__((section(".data.page_aligned"))) = + { [ 0 ... TOP_ENTRIES - 1] = &p2m_missing[0] }; static inline unsigned p2m_top_index(unsigned long pfn) { @@ -92,9 +101,6 @@ unsigned long get_phys_to_machine(unsigned long pfn) return INVALID_P2M_ENTRY; topidx = p2m_top_index(pfn); - if (p2m_top[topidx] == NULL) - return INVALID_P2M_ENTRY; - idx = p2m_index(pfn); return p2m_top[topidx][idx]; } @@ -110,7 +116,7 @@ static void alloc_p2m(unsigned long **pp) for(i = 0; i < P2M_ENTRIES_PER_PAGE; i++) p[i] = INVALID_P2M_ENTRY; - if (cmpxchg(pp, NULL, p) != NULL) + if (cmpxchg(pp, p2m_missing, p) != p2m_missing) free_page((unsigned long)p); } @@ -129,7 +135,7 @@ void set_phys_to_machine(unsigned long pfn, unsigned long mfn) } topidx = p2m_top_index(pfn); - if (p2m_top[topidx] == NULL) { + if (p2m_top[topidx] == p2m_missing) { /* no need to allocate a page to store an invalid entry */ if (mfn == INVALID_P2M_ENTRY) return; |