From d320b19cacb31ca9154682d623dd004eb0681843 Mon Sep 17 00:00:00 2001
From: Radim Krcmar <rkrcmar@redhat.com>
Date: Mon, 10 Mar 2014 15:14:27 +0100
Subject: Workaround for a win8.1-32 S4 resume bug
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RH-Author: Radim Krcmar <rkrcmar@redhat.com>
Message-id: <1394464467-23560-1-git-send-email-rkrcmar@redhat.com>
Patchwork-id: 58069
O-Subject: [RHEL7.0 seabios PATCH] Workaround for a win8.1-32 S4 resume bug
Bugzilla: 1050775
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Gerd Hoffmann <kraxel@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>

bug:  https://bugzilla.redhat.com/show_bug.cgi?id=1050775
brew: http://brewweb.devel.redhat.com/brew/taskinfo?taskID=7176174
This patch has no upstream equivalent.

When a 32 bit version of windows 8.1 resumes from suspend, it writes 1
into 0x72 in the early boot because it didn't expect a NULL pointer.
0x72 is lower offset byte of 0x1c interrupt entry, so we jump into a
middle of other function if this interrupt is triggered.

Because 0x1c is only triggered from our handle_08, we detect if our
default value (function that does only iret) has its lower offset byte
overwritten and skip it in that case.
(Windows never sets own callback there, so we always detect this bug
 correctly, as seabios doesn't use it either
 Other sources shouldn't incorrectly overwrite it or use seabios code,
 but it is quite ok even if the guest did this on purpose.)

The reason Windows uses NULL pointer is still unknown, but this bug is
blocking WHQL certification, so we have to work around it in 7.0.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
 src/clock.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/clock.c b/src/clock.c
index e44e112..298a722 100644
--- a/src/clock.c
+++ b/src/clock.c
@@ -309,7 +309,13 @@ handle_08(void)
     struct bregs br;
     memset(&br, 0, sizeof(br));
     br.flags = F_IF;
-    call16_int(0x1c, &br);
+    struct segoff_s isr1c = GET_IVT(0x1c);
+    // hardcoded address of entry_iret_official with lower segment byte
+    // overwritten by 1
+    if (isr1c.seg == ((SEG_BIOS & ~0xff) | 0x1) && isr1c.offset == 0xff53)
+        dprintf(1, "Worked around win8.1-32 S4 resume bug\n");
+    else
+        call16_int(0x1c, &br);
 
     pic_eoi1();
 }
-- 
2.18.4