mb/emulation/qemu: Copy page tables to DRAM in assembly
To work around various bugs running KVM enabled, copy page tables to
DRAM in assembly before jumping to x86_64 mode.
Tested on QEMU using KVM, no more stange bugs happen:
Tested on host
- CPU Intel(R) Core(TM) i7-7700HQ
- Linux 5.9
- qemu 4.2.1
Used to crash on emulating MMX instructions and failed to translate
some addresses using the virtual MMU when running in long mode.
Tested on host
- CPU AMD EPYC 7401P 24-Core Processor
- Linux 5.4
- qemu 4.2.1
Used to crash on jumping to long mode.
Change-Id: Ic0bdd2bef7197edd2e7488a8efdeba7eb4ab0dd4
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49228
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/src/cpu/qemu-x86/cache_as_ram_bootblock.S b/src/cpu/qemu-x86/cache_as_ram_bootblock.S
index e3a26b0..07f848a 100644
--- a/src/cpu/qemu-x86/cache_as_ram_bootblock.S
+++ b/src/cpu/qemu-x86/cache_as_ram_bootblock.S
@@ -2,7 +2,14 @@
#include <cpu/x86/post_code.h>
+#define CBFS_FILE_MAGIC 0
+#define CBFS_FILE_LEN (CBFS_FILE_MAGIC + 8)
+#define CBFS_FILE_TYPE (CBFS_FILE_LEN + 4)
+#define CBFS_FILE_CHECKSUM (CBFS_FILE_TYPE + 4)
+#define CBFS_FILE_OFFSET (CBFS_FILE_CHECKSUM + 4)
+
.section .init, "ax", @progbits
+.code32
.global bootblock_pre_c_entry
bootblock_pre_c_entry:
@@ -24,12 +31,55 @@
post_code(0x21)
+#if defined(__x86_64__)
+ /*
+ * Copy page tables to final location in DRAM. This prevents some strange
+ * bugs when running KVM enabled:
+ * Accessing MMX instructions in long mode causes an abort
+ * Some physical addresses aren't properly translated
+ * Emulation fault on every instruction fetched due to page tables in ROM
+ * Enabling or disabling paging causes a fault
+ *
+ * First, find page tables in CBFS:
+ */
+ lea pagetables_name, %esi
+ mov $1f, %esp
+ jmp walkcbfs_asm
+1:
+ cmpl $0, %eax
+ je .Lhlt
+
+ /* Test if page tables are memory-mapped and skip relocation */
+ cmpl $(CONFIG_ARCH_X86_64_PGTBL_LOC), %eax
+ je pages_done
+
+ movl CBFS_FILE_OFFSET(%eax), %ebx
+ bswap %ebx
+ addl %eax, %ebx
+ movl %ebx, %esi
+
+ movl CBFS_FILE_LEN(%eax), %ecx
+ bswap %ecx
+ shr $2, %ecx
+
+ movl $(CONFIG_ARCH_X86_64_PGTBL_LOC), %edi
+
+loop:
+ movl (%esi), %eax
+ movl %eax, (%edi)
+ addl $4, %esi
+ addl $4, %edi
+ decl %ecx
+ jnz loop
+pages_done:
+#endif
+
movl $_ecar_stack, %esp
/* Align the stack and keep aligned for call to bootblock_c_entry() */
and $0xfffffff0, %esp
- /* entry64.inc preserves ebx. */
+ /* entry64.inc preserves ebx. */
#include <cpu/x86/64bit/entry64.inc>
/* Restore the BIST result and timestamps. */
@@ -60,3 +110,6 @@
post_code(POST_DEAD_CODE)
hlt
jmp .Lhlt
+
+pagetables_name:
+ .string "pagetables"