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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH] xen/x86: Use 2M superpages for text/data/bss mappings
This balloons the size of Xen in memory from 3.4MB to 12MB, because of the
required alignment adjustments.
However
* All mappings are 2M superpages.
* .text (and .init at boot) are the only sections marked executable.
* .text and .rodata are marked read-only.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
xen/arch/x86/setup.c | 44 +++++++++++++++++++++++++++++++++++++++++---
xen/arch/x86/xen.lds.S | 33 +++++++++++++++++++++++++++++++++
xen/include/xen/kernel.h | 6 ++++++
3 files changed, 80 insertions(+), 3 deletions(-)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index cddf954..c360fbc 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -921,13 +921,51 @@ void __init noreturn __start_xen(unsigned long mbi_p)
/* The only data mappings to be relocated are in the Xen area. */
pl2e = __va(__pa(l2_xenmap));
*pl2e++ = l2e_from_pfn(xen_phys_start >> PAGE_SHIFT,
- PAGE_HYPERVISOR_RWX | _PAGE_PSE);
+ PAGE_HYPERVISOR_RX | _PAGE_PSE);
for ( i = 1; i < L2_PAGETABLE_ENTRIES; i++, pl2e++ )
{
+ unsigned int flags;
+
if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) )
continue;
- *pl2e = l2e_from_intpte(l2e_get_intpte(*pl2e) +
- xen_phys_start);
+
+ if ( /*
+ * Should be:
+ *
+ * i >= l2_table_offset((unsigned long)&__2M_text_start)
&&
+ *
+ * but the EFI build can't manage the relocation. It
+ * evaluates to 0, so just use the upper bound.
+ */
+ i < l2_table_offset((unsigned long)&__2M_text_end) )
+ {
+ flags = PAGE_HYPERVISOR_RX | _PAGE_PSE;
+ }
+ else if ( i >= l2_table_offset((unsigned
long)&__2M_rodata_start) &&
+ i < l2_table_offset((unsigned
long)&__2M_rodata_end) )
+ {
+ flags = PAGE_HYPERVISOR_RO | _PAGE_PSE;
+ }
+ else if ( (i >= l2_table_offset((unsigned
long)&__2M_data_start) &&
+ i < l2_table_offset((unsigned
long)&__2M_data_end)) ||
+ (i >= l2_table_offset((unsigned
long)&__2M_bss_start) &&
+ i < l2_table_offset((unsigned long)&__2M_bss_end))
)
+ {
+ flags = PAGE_HYPERVISOR_RW | _PAGE_PSE;
+ }
+ else if ( i >= l2_table_offset((unsigned
long)&__2M_init_start) &&
+ i < l2_table_offset((unsigned long)&__2M_init_end) )
+ {
+ flags = PAGE_HYPERVISOR_RWX | _PAGE_PSE;
+ }
+ else
+ {
+ *pl2e = l2e_empty();
+ continue;
+ }
+
+ *pl2e = l2e_from_paddr(
+ l2e_get_paddr(*pl2e) + xen_phys_start, flags);
}
/* Re-sync the stack and then switch to relocated pagetables. */
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 9fde1db..6c23c02 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -38,6 +38,9 @@ SECTIONS
. = __XEN_VIRT_START;
__image_base__ = .;
#endif
+
+ __2M_text_start = .; /* Start of 2M superpages, mapped RX. */
+
. = __XEN_VIRT_START + MB(1);
_start = .;
.text : {
@@ -50,6 +53,10 @@ SECTIONS
_etext = .; /* End of text section */
} :text = 0x9090
+ . = ALIGN(MB(2));
+ __2M_text_end = .;
+
+ __2M_rodata_start = .; /* Start of 2M superpages, mapped RO. */
.rodata : {
/* Bug frames table */
. = ALIGN(4);
@@ -67,6 +74,10 @@ SECTIONS
*(.rodata.*)
} :text
+ . = ALIGN(MB(2));
+ __2M_rodata_end = .;
+
+ __2M_data_start = .; /* Start of 2M superpages, mapped RW. */
. = ALIGN(SMP_CACHE_BYTES);
.data.read_mostly : {
/* Exception table */
@@ -104,6 +115,10 @@ SECTIONS
__lock_profile_end = .;
#endif
+ . = ALIGN(MB(2));
+ __2M_data_end = .;
+
+ __2M_init_start = .; /* Start of 2M superpages, mapped RWX (boot
only). */
. = ALIGN(PAGE_SIZE); /* Init code and data */
__init_begin = .;
.init.text : {
@@ -166,6 +181,10 @@ SECTIONS
. = ALIGN(STACK_SIZE);
__init_end = .;
+ . = ALIGN(MB(2));
+ __2M_init_end = .;
+
+ __2M_bss_start = .; /* Start of 2M superpages, mapped RW. */
.bss : { /* BSS */
__bss_start = .;
*(.bss.stack_aligned)
@@ -183,6 +202,9 @@ SECTIONS
} :text
_end = . ;
+ . = ALIGN(MB(2));
+ __2M_bss_end = .;
+
#ifdef EFI
. = ALIGN(4);
.reloc : {
@@ -229,4 +251,15 @@ ASSERT(__image_base__ > XEN_VIRT_START ||
ASSERT(kexec_reloc_size - kexec_reloc <= PAGE_SIZE, "kexec_reloc is too large")
#endif
+ASSERT(IS_ALIGNED(__2M_text_start, MB(2)), "__2M_text_start misaligned")
+ASSERT(IS_ALIGNED(__2M_text_end, MB(2)), "__2M_text_end misaligned")
+ASSERT(IS_ALIGNED(__2M_rodata_start, MB(2)), "__2M_rodata_start misaligned")
+ASSERT(IS_ALIGNED(__2M_rodata_end, MB(2)), "__2M_rodata_end misaligned")
+ASSERT(IS_ALIGNED(__2M_data_start, MB(2)), "__2M_data_start misaligned")
+ASSERT(IS_ALIGNED(__2M_data_end, MB(2)), "__2M_data_end misaligned")
+ASSERT(IS_ALIGNED(__2M_init_start, MB(2)), "__2M_init_start misaligned")
+ASSERT(IS_ALIGNED(__2M_init_end, MB(2)), "__2M_init_end misaligned")
+ASSERT(IS_ALIGNED(__2M_bss_start, MB(2)), "__2M_bss_start misaligned")
+ASSERT(IS_ALIGNED(__2M_bss_end, MB(2)), "__2M_bss_end misaligned")
+
ASSERT(IS_ALIGNED(cpu0_stack, STACK_SIZE), "cpu0_stack misaligned")
diff --git a/xen/include/xen/kernel.h b/xen/include/xen/kernel.h
index 548b64d..8d08eca 100644
--- a/xen/include/xen/kernel.h
+++ b/xen/include/xen/kernel.h
@@ -65,6 +65,12 @@
1; \
})
+extern unsigned long __2M_text_start[], __2M_text_end[];
+extern unsigned long __2M_rodata_start[], __2M_rodata_end[];
+extern unsigned long __2M_data_start[], __2M_data_end[];
+extern unsigned long __2M_init_start[], __2M_init_end[];
+extern unsigned long __2M_bss_start[], __2M_bss_end[];
+
extern char _start[], _end[], start[];
#define is_kernel(p) ({ \
char *__p = (char *)(unsigned long)(p); \
--
2.1.4
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