From 8629f200084ce1aab31d193280d34b5fb16e543f Mon Sep 17 00:00:00 2001 From: Radim Krcmar Date: Mon, 10 Mar 2014 15:14:27 +0100 Subject: Workaround for a win8.1-32 S4 resume bug MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Radim Krcmar 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 RH-Acked-by: Gerd Hoffmann RH-Acked-by: Laszlo Ersek 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 --- 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(); } -- 2.27.0