[SeaBIOS] [PATCH] smm: ignore bits 16,18-31 of SMM revision ID

[Paolo Bonzini]

Bits 16-31 of the SMM revision ID are feature bits.  We only need to
check that SMBASE relocation is supported, but do not care about other
features.  In particular, this allows the SMM I/O instruction restart
feature to be present.

Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
---
 src/fw/smm.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/fw/smm.c b/src/fw/smm.c
index dabc677..6cb484e 100644
--- a/src/fw/smm.c
+++ b/src/fw/smm.c
@@ -18,8 +18,14 @@
 #include "util.h" // smm_setup
 #include "x86.h" // wbinvd
 
-#define SMM_REV_I32 0x00020000
-#define SMM_REV_I64 0x00020064
+/*
+ * Check SMM state save area format (bits 0-15) and require support
+ * for SMBASE relocation.
+ */
+#define SMM_REV_MASK 0x0002ffff
+
+#define SMM_REV_I32  0x00020000
+#define SMM_REV_I64  0x00020064
 
 struct smm_state {
     union {
@@ -62,9 +68,10 @@ handle_smi(u16 cs)
 
     if (smm == (void*)BUILD_SMM_INIT_ADDR) {
         // relocate SMBASE to 0xa0000
-        if (smm->cpu.i32.smm_rev == SMM_REV_I32) {
+        u32 rev = smm->cpu.i32.smm_rev & SMM_REV_MASK;
+        if (rev == SMM_REV_I32) {
             smm->cpu.i32.smm_base = BUILD_SMM_ADDR;
-        } else if (smm->cpu.i64.smm_rev == SMM_REV_I64) {
+        } else if (rev == SMM_REV_I64) {
             smm->cpu.i64.smm_base = BUILD_SMM_ADDR;
         } else {
             warn_internalerror();
-- 
2.3.5