diff options
Diffstat (limited to '0003-x86-rtc-Avoid-UIP-flag-being-set-for-longer-than-exp.patch')
| -rw-r--r-- | 0003-x86-rtc-Avoid-UIP-flag-being-set-for-longer-than-exp.patch | 57 |
1 files changed, 0 insertions, 57 deletions
diff --git a/0003-x86-rtc-Avoid-UIP-flag-being-set-for-longer-than-exp.patch b/0003-x86-rtc-Avoid-UIP-flag-being-set-for-longer-than-exp.patch deleted file mode 100644 index 8307630..0000000 --- a/0003-x86-rtc-Avoid-UIP-flag-being-set-for-longer-than-exp.patch +++ /dev/null @@ -1,57 +0,0 @@ -From af0e9ba44a58c87d6d135d8ffbf468b4ceac0a41 Mon Sep 17 00:00:00 2001 -From: Ross Lagerwall <ross.lagerwall@citrix.com> -Date: Mon, 29 Apr 2024 09:36:04 +0200 -Subject: [PATCH 03/56] x86/rtc: Avoid UIP flag being set for longer than - expected - -In a test, OVMF reported an error initializing the RTC without -indicating the precise nature of the error. The only plausible -explanation I can find is as follows: - -As part of the initialization, OVMF reads register C and then reads -register A repatedly until the UIP flag is not set. If this takes longer -than 100 ms, OVMF fails and reports an error. This may happen with the -following sequence of events: - -At guest time=0s, rtc_init() calls check_update_timer() which schedules -update_timer for t=(1 - 244us). - -At t=1s, the update_timer function happens to have been called >= 244us -late. In the timer callback, it sets the UIP flag and schedules -update_timer2 for t=1s. - -Before update_timer2 runs, the guest reads register C which calls -check_update_timer(). check_update_timer() stops the scheduled -update_timer2 and since the guest time is now outside of the update -cycle, it schedules update_timer for t=(2 - 244us). - -The UIP flag will therefore be set for a whole second from t=1 to t=2 -while the guest repeatedly reads register A waiting for the UIP flag to -clear. Fix it by clearing the UIP flag when scheduling update_timer. - -I was able to reproduce this issue with a synthetic test and this -resolves the issue. - -Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com> -Reviewed-by: Jan Beulich <jbeulich@suse.com> -master commit: 43a07069863b419433dee12c9b58c1f7ce70aa97 -master date: 2024-04-23 14:09:18 +0200 ---- - xen/arch/x86/hvm/rtc.c | 1 + - 1 file changed, 1 insertion(+) - -diff --git a/xen/arch/x86/hvm/rtc.c b/xen/arch/x86/hvm/rtc.c -index 206b4296e9..4839374352 100644 ---- a/xen/arch/x86/hvm/rtc.c -+++ b/xen/arch/x86/hvm/rtc.c -@@ -202,6 +202,7 @@ static void check_update_timer(RTCState *s) - } - else - { -+ s->hw.cmos_data[RTC_REG_A] &= ~RTC_UIP; - next_update_time = (USEC_PER_SEC - guest_usec - 244) * NS_PER_USEC; - expire_time = NOW() + next_update_time; - s->next_update_time = expire_time; --- -2.45.2 - |