aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/lguest/lg.h
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/lguest/lg.h')
-rw-r--r--drivers/lguest/lg.h19
1 files changed, 16 insertions, 3 deletions
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index 3b9dc123a7d..269116eee85 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -58,9 +58,18 @@ struct lguest_dma_info
58 u8 interrupt; /* 0 when not registered */ 58 u8 interrupt; /* 0 when not registered */
59}; 59};
60 60
61/* We have separate types for the guest's ptes & pgds and the shadow ptes & 61/*H:310 The page-table code owes a great debt of gratitude to Andi Kleen. He
62 * pgds. Since this host might use three-level pagetables and the guest and 62 * reviewed the original code which used "u32" for all page table entries, and
63 * shadow pagetables don't, we can't use the normal pte_t/pgd_t. */ 63 * insisted that it would be far clearer with explicit typing. I thought it
64 * was overkill, but he was right: it is much clearer than it was before.
65 *
66 * We have separate types for the Guest's ptes & pgds and the shadow ptes &
67 * pgds. There's already a Linux type for these (pte_t and pgd_t) but they
68 * change depending on kernel config options (PAE). */
69
70/* Each entry is identical: lower 12 bits of flags and upper 20 bits for the
71 * "page frame number" (0 == first physical page, etc). They are different
72 * types so the compiler will warn us if we mix them improperly. */
64typedef union { 73typedef union {
65 struct { unsigned flags:12, pfn:20; }; 74 struct { unsigned flags:12, pfn:20; };
66 struct { unsigned long val; } raw; 75 struct { unsigned long val; } raw;
@@ -77,8 +86,12 @@ typedef union {
77 struct { unsigned flags:12, pfn:20; }; 86 struct { unsigned flags:12, pfn:20; };
78 struct { unsigned long val; } raw; 87 struct { unsigned long val; } raw;
79} gpte_t; 88} gpte_t;
89
90/* We have two convenient macros to convert a "raw" value as handed to us by
91 * the Guest into the correct Guest PGD or PTE type. */
80#define mkgpte(_val) ((gpte_t){.raw.val = _val}) 92#define mkgpte(_val) ((gpte_t){.raw.val = _val})
81#define mkgpgd(_val) ((gpgd_t){.raw.val = _val}) 93#define mkgpgd(_val) ((gpgd_t){.raw.val = _val})
94/*:*/
82 95
83struct pgdir 96struct pgdir
84{ 97{