QEMU does not store the A20 setting in the SMM cpu environment area
(and it does not look like real CPUs do either). So, manually backup
and restore A20 on a mode switch.
Signed-off-by: Kevin O'Connor <kevin(a)koconnor.net>
---
src/fw/smm.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/src/fw/smm.c b/src/fw/smm.c
index 95f6ba7..178959c 100644
--- a/src/fw/smm.c
+++ b/src/fw/smm.c
@@ -52,7 +52,8 @@ struct smm_state {
struct smm_layout {
struct smm_state backup1;
struct smm_state backup2;
- u8 stack[0x7c00];
+ u32 backup_a20;
+ u8 stack[0x8000 - sizeof(struct smm_state)*2 - sizeof(u32)];
u64 codeentry;
u8 pad_8008[0x7df8];
struct smm_state cpu;
@@ -102,10 +103,13 @@ handle_smi(u16 cs)
memcpy(&smm->cpu, &smm->backup1, sizeof(smm->cpu));
memcpy(&smm->cpu.i32.eax, regs, sizeof(regs));
smm->cpu.i32.eip = regs[3];
+ // Enable a20 and backup its previous state
+ smm->backup_a20 = set_a20(1);
} else if (smm->cpu.i32.ecx == CALL32SMM_RETURNID) {
dprintf(9, "smm cpu ret %x esp=%x\n", regs[3], regs[4]);
memcpy(&smm->cpu, &smm->backup2, sizeof(smm->cpu));
memcpy(&smm->cpu.i32.eax, regs, sizeof(regs));
+ set_a20(smm->backup_a20);
smm->cpu.i32.eip = regs[3];
}
} else if (rev == SMM_REV_I64) {
@@ -116,9 +120,12 @@ handle_smi(u16 cs)
memcpy(&smm->cpu, &smm->backup1, sizeof(smm->cpu));
memcpy(&smm->cpu.i64.rdi, regs, sizeof(regs));
smm->cpu.i64.rip = (u32)regs[4];
+ // Enable a20 and backup its previous state
+ smm->backup_a20 = set_a20(1);
} else if ((u32)smm->cpu.i64.rcx == CALL32SMM_RETURNID) {
memcpy(&smm->cpu, &smm->backup2, sizeof(smm->cpu));
memcpy(&smm->cpu.i64.rdi, regs, sizeof(regs));
+ set_a20(smm->backup_a20);
smm->cpu.i64.rip = (u32)regs[4];
}
}
--
2.9.3