@@ -387,10 +387,6 @@ SYM_CODE_START(startup_64)
* For the trampoline, we need the top page table to reside in lower
* memory as we don't have a way to load 64-bit values into CR3 in
* 32-bit mode.
- *
- * We go though the trampoline even if we don't have to: if we're
- * already in a desired paging mode. This way the trampoline code gets
- * tested on every boot.
*/
/* Make sure we have GDT with 32-bit code segment */
@@ -526,8 +522,7 @@ SYM_FUNC_END(.Lrelocated)
*
* Return address is at the top of the stack (might be above 4G).
* The first argument (EDI) contains the 32-bit addressable base of the
- * trampoline memory. A non-zero second argument (ESI) means that the
- * trampoline needs to enable 5-level paging.
+ * trampoline memory.
*/
.section ".rodata", "a", @progbits
SYM_CODE_START(trampoline_32bit_src)
@@ -579,25 +574,10 @@ SYM_CODE_START(trampoline_32bit_src)
btrl $X86_CR0_PG_BIT, %eax
movl %eax, %cr0
- /* Check what paging mode we want to be in after the trampoline */
- testl %esi, %esi
- jz 1f
-
- /* We want 5-level paging: don't touch CR3 if it already points to 5-level page tables */
- movl %cr4, %eax
- testl $X86_CR4_LA57, %eax
- jnz 3f
- jmp 2f
-1:
- /* We want 4-level paging: don't touch CR3 if it already points to 4-level page tables */
- movl %cr4, %eax
- testl $X86_CR4_LA57, %eax
- jz 3f
-2:
/* Point CR3 to the trampoline's new top level page table */
leal TRAMPOLINE_32BIT_PGTABLE_OFFSET(%edi), %eax
movl %eax, %cr3
-3:
+
/* Set EFER.LME=1 as a precaution in case hypervsior pulls the rug */
movl $MSR_EFER, %ecx
rdmsr
@@ -606,26 +586,9 @@ SYM_CODE_START(trampoline_32bit_src)
jc 1f
wrmsr
1:
-#ifdef CONFIG_X86_MCE
- /*
- * Preserve CR4.MCE if the kernel will enable #MC support.
- * Clearing MCE may fault in some environments (that also force #MC
- * support). Any machine check that occurs before #MC support is fully
- * configured will crash the system regardless of the CR4.MCE value set
- * here.
- */
+ /* Toggle CR4.LA57 */
movl %cr4, %eax
- andl $X86_CR4_MCE, %eax
-#else
- movl $0, %eax
-#endif
-
- /* Enable PAE and LA57 (if required) paging modes */
- orl $X86_CR4_PAE, %eax
- testl %esi, %esi
- jz 1f
- orl $X86_CR4_LA57, %eax
-1:
+ btcl $X86_CR4_LA57_BIT, %eax
movl %eax, %cr4
/* Enable paging again. */
@@ -103,7 +103,7 @@ static unsigned long find_trampoline_placement(void)
asmlinkage void configure_5level_paging(struct boot_params *bp)
{
- void (*toggle_la57)(void *trampoline, bool enable_5lvl);
+ void (*toggle_la57)(void *trampoline);
bool l5_required = false;
/* Initialize boot_params. Required for cmdline_find_option_bool(). */
@@ -133,6 +133,13 @@ asmlinkage void configure_5level_paging(struct boot_params *bp)
ptrs_per_p4d = 512;
}
+ /*
+ * The trampoline will not be used if the paging mode is already set to
+ * the desired one.
+ */
+ if (l5_required == !!(native_read_cr4() & X86_CR4_LA57))
+ return;
+
trampoline_32bit = (unsigned long *)find_trampoline_placement();
/* Preserve trampoline memory */
@@ -160,18 +167,8 @@ asmlinkage void configure_5level_paging(struct boot_params *bp)
*
* The new page table will be used by trampoline code for switching
* from 4- to 5-level paging or vice versa.
- *
- * If switching is not required, the page table is unused: trampoline
- * code wouldn't touch CR3.
*/
- /*
- * We are not going to use the page table in trampoline memory if we
- * are already in the desired paging mode.
- */
- if (l5_required == !!(native_read_cr4() & X86_CR4_LA57))
- goto out;
-
if (l5_required) {
/*
* For 4- to 5-level paging transition, set up current CR3 as
@@ -194,8 +191,7 @@ asmlinkage void configure_5level_paging(struct boot_params *bp)
(void *)src, PAGE_SIZE);
}
-out:
- toggle_la57(trampoline_32bit, l5_required);
+ toggle_la57(trampoline_32bit);
}
void cleanup_trampoline(void *pgtable)