}
__setup("debugpat", pat_debug_setup);
-static u64 __read_mostly boot_pat_state;
-
#ifdef CONFIG_X86_PAT
/*
* X86 PAT uses page flags WC and Uncached together to keep track of
* configuration.
* Using lower indices is preferred, so we start with highest index.
*/
-void pat_init_cache_modes(void)
+void pat_init_cache_modes(u64 pat)
{
- int i;
enum page_cache_mode cache;
char pat_msg[33];
- u64 pat;
+ int i;
- rdmsrl(MSR_IA32_CR_PAT, pat);
pat_msg[32] = 0;
for (i = 7; i >= 0; i--) {
cache = pat_get_cache_mode((pat >> (i * 8)) & 7,
static void pat_bsp_init(u64 pat)
{
+ u64 tmp_pat;
+
if (!cpu_has_pat) {
pat_disable("PAT not supported by CPU.");
return;
}
- rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);
- if (!boot_pat_state) {
+ if (!pat_enabled())
+ goto done;
+
+ rdmsrl(MSR_IA32_CR_PAT, tmp_pat);
+ if (!tmp_pat) {
pat_disable("PAT MSR is 0, disabled.");
return;
}
wrmsrl(MSR_IA32_CR_PAT, pat);
- pat_init_cache_modes();
+done:
+ pat_init_cache_modes(pat);
}
static void pat_ap_init(u64 pat)
{
+ if (!pat_enabled())
+ return;
+
if (!cpu_has_pat) {
/*
* If this happens we are on a secondary CPU, but switched to
{
u64 pat;
- if (!pat_enabled())
- return;
-
- /*
- * Set PWT to Write-Combining. All other bits stay the same:
- *
- * PTE encoding used in Linux:
- * PAT
- * |PCD
- * ||PWT
- * |||
- * 000 WB _PAGE_CACHE_WB
- * 001 WC _PAGE_CACHE_WC
- * 010 UC- _PAGE_CACHE_UC_MINUS
- * 011 UC _PAGE_CACHE_UC
- * PAT bit unused
- */
- pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
- PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+ if (!pat_enabled()) {
+ /*
+ * No PAT. Emulate the PAT table that corresponds to the two
+ * cache bits, PWT (Write Through) and PCD (Cache Disable). This
+ * setup is the same as the BIOS default setup when the system
+ * has PAT but the "nopat" boot option has been specified. This
+ * emulated PAT table is used when MSR_IA32_CR_PAT returns 0.
+ *
+ * PTE encoding used:
+ *
+ * PCD
+ * |PWT PAT
+ * || slot
+ * 00 0 WB : _PAGE_CACHE_MODE_WB
+ * 01 1 WT : _PAGE_CACHE_MODE_WT
+ * 10 2 UC-: _PAGE_CACHE_MODE_UC_MINUS
+ * 11 3 UC : _PAGE_CACHE_MODE_UC
+ *
+ * NOTE: When WC or WP is used, it is redirected to UC- per
+ * the default setup in __cachemode2pte_tbl[].
+ */
+ pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) |
+ PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
+ } else {
+ /*
+ * PTE encoding used in Linux:
+ * PAT
+ * |PCD
+ * ||PWT
+ * |||
+ * 000 WB _PAGE_CACHE_WB
+ * 001 WC _PAGE_CACHE_WC
+ * 010 UC- _PAGE_CACHE_UC_MINUS
+ * 011 UC _PAGE_CACHE_UC
+ * PAT bit unused
+ */
+ pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
+ PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);
+ }
if (!boot_cpu_done) {
pat_bsp_init(pat);