Previously, Xen used information from the BDA to detect the amount of
available low memory. This does not work on some scenarios such as
Coreboot, or when booting from Kexec on a UEFI system without CSM.
Use the information directly supplied by Multiboot boot information
instead.
---
xen/arch/x86/boot/head.S | 34 ++++++++++++----------------------
1 file changed, 12 insertions(+), 22 deletions(-)
diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index dd1bea0d10..62fe3fe55b 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -524,33 +524,23 @@ trampoline_bios_setup:
mov %ecx,%fs
mov %ecx,%gs
- /* Set up trampoline segment 64k below EBDA */
- movzwl 0x40e,%ecx /* EBDA segment */
- cmp $0xa000,%ecx /* sanity check (high) */
- jae 0f
- cmp $0x4000,%ecx /* sanity check (low) */
- jae 1f
-0:
- movzwl 0x413,%ecx /* use base memory size on failure */
- shl $10-4,%ecx
-1:
+ /* Use lower memory size directly from Multiboot */
+ mov %edx,%ecx
/*
- * Compare the value in the BDA with the information from the
- * multiboot structure (if available) and use the smallest.
+ * Old Kexec used to report the value in bytes instead of kilobytes
+ * like it's supposed to, so fix that if detected.
*/
- cmp $0x100,%edx /* is the multiboot value too small? */
- jb 2f /* if so, do not use it */
- shl $10-4,%edx
- cmp %ecx,%edx /* compare with BDA value */
- cmovb %edx,%ecx /* and use the smaller */
+ cmpl $640,%ecx
+ jbe 1f
+ shr $10,%ecx
+1:
+ /* From arch/x86/smpboot.c: start_eip had better be page-aligned! */
+ shr $2,%ecx
-2:
/* Reserve memory for the trampoline and the low-memory stack. */
- sub $((TRAMPOLINE_SPACE+TRAMPOLINE_STACK_SPACE)>>4),%ecx
+ sub $((TRAMPOLINE_SPACE+TRAMPOLINE_STACK_SPACE)>>12),%ecx
- /* From arch/x86/smpboot.c: start_eip had better be page-aligned! */
- xor %cl, %cl
- shl $4, %ecx
+ shl $12,%ecx
mov %ecx,sym_esi(trampoline_phys)
trampoline_setup:
--
2.25.1
