[SeaBIOS] [PATCH 1/2] resume: Make KVM soft reboot loop detection more flexible

[Kevin O'Connor]

Move the check for soft reboot loops from resume.c to shadow.c and
directly check for the case where the copy of the BIOS in flash
appears to be a memory alias instead.  This prevents a hang if an
external reboot request occurs during the BIOS memcpy.

Signed-off-by: Kevin O'Connor <kevin at koconnor.net>
---
 src/fw/shadow.c | 15 +++++++++++++--
 src/resume.c    |  9 ---------
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/fw/shadow.c b/src/fw/shadow.c
index ee87d36..4486884 100644
--- a/src/fw/shadow.c
+++ b/src/fw/shadow.c
@@ -163,7 +163,18 @@ qemu_prep_reset(void)
         return;
     // QEMU doesn't map 0xc0000-0xfffff back to the original rom on a
     // reset, so do that manually before invoking a hard reset.
+    void *cstart = VSYMBOL(code32flat_start), *cend = VSYMBOL(code32flat_end);
+    void *hrp = &HaveRunPost;
+    if (readl(hrp + BIOS_SRC_OFFSET)) {
+        // Some old versions of KVM don't store a pristine copy of the
+        // BIOS in high memory.  Try to shutdown the machine instead.
+        dprintf(1, "Unable to hard-reboot machine - attempting shutdown.\n");
+        apm_shutdown();
+    }
+    // Copy the BIOS making sure to only reset HaveRunPost at end
     make_bios_writable();
-    memcpy(VSYMBOL(code32flat_start), VSYMBOL(code32flat_start) + BIOS_SRC_OFFSET
-           , SYMBOL(code32flat_end) - SYMBOL(code32flat_start));
+    memcpy(cstart, cstart + BIOS_SRC_OFFSET, hrp - cstart);
+    memcpy(hrp + 4, hrp + 4 + BIOS_SRC_OFFSET, cend - (hrp + 4));
+    barrier();
+    HaveRunPost = 0;
 }
diff --git a/src/resume.c b/src/resume.c
index a5465d8..afeadcf 100644
--- a/src/resume.c
+++ b/src/resume.c
@@ -114,19 +114,10 @@ s3_resume(void)
     farcall16big(&br);
 }
 
-u8 HaveAttemptedReboot VARLOW;
-
 // Attempt to invoke a hard-reboot.
 static void
 tryReboot(void)
 {
-    if (HaveAttemptedReboot) {
-        // Hard reboot has failed - try to shutdown machine.
-        dprintf(1, "Unable to hard-reboot machine - attempting shutdown.\n");
-        apm_shutdown();
-    }
-    HaveAttemptedReboot = 1;
-
     dprintf(1, "Attempting a hard reboot\n");
 
     // Setup for reset on qemu.
-- 
2.5.0