** Changed in: linux-azure (Ubuntu Focal)
Status: In Progress => Fix Committed
--
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux-azure in Ubuntu.
https://bugs.launchpad.net/bugs/1977753
Title:
Azure 5.4: vDSO broken with 5.4.0-1075-azure
Status in linux-azure package in Ubuntu:
Fix Released
Status in linux-azure source package in Focal:
Fix Committed
Bug description:
SRU Justification
[Impact]
vDSO works with the 5.4.0-1074-azure kernel, but is broken in
5.4.0-1075-azure and newer due to this commit
https://git.launchpad.net/~canonical-kernel/ubuntu/+source/linux-azure/+git/bionic/commit/?h=Ubuntu-azure-5.4-5.4.0-1075.78_18.04.1&id=5c899e1bcda02c755a5327353ed66f0768771644
Please revert the commit 5c899e1bcda02c755a5327353ed66f0768771644.
How to verify vDSO is working: "strace date 2>&1 | grep time" should not show
the time related syscalls, e.g. clock_gettime()
With 5.4.0-1075-azure and newer, I see the time related syscalls.
****************************************************************
More info:
The buggy commit 5c899e1bcda02c755a5327353ed66f0768771644 was backported from
the mainline commit:
e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO differences inline")
but due to the differences between the mainline kernel and the
5.4.0-107x-azure kernel, we actually should not simply remove
hv_set_clocksource_vdso().
FWIW, the mainline commit is actually buggy and is fixed by this later
mainline path:
commit 3486d2c9be652a31033363bdd50391b0c8a8fe21
Author: Vitaly Kuznetsov [email protected]
Date: Thu May 13 09:32:46 2021 +0200
clocksource/drivers/hyper-v: Re-enable VDSO_CLOCKMODE_HVCLOCK on X86
Mohammed reports (https://bugzilla.kernel.org/show_bug.cgi?id=213029)
the commit e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO
differences inline") broke vDSO on x86. The problem appears to be that
VDSO_CLOCKMODE_HVCLOCK is an enum value in 'enum vdso_clock_mode' and
'#ifdef VDSO_CLOCKMODE_HVCLOCK' branch evaluates to false (it is not
a define).
Use a dedicated HAVE_VDSO_CLOCKMODE_HVCLOCK define instead.
Fixes: e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO differences
inline")
Reported-by: Mohammed Gamal [email protected]
Suggested-by: Thomas Gleixner [email protected]
Signed-off-by: Vitaly Kuznetsov [email protected]
Signed-off-by: Thomas Gleixner [email protected]
Reviewed-by: Michael Kelley [email protected]
Link: https://lore.kernel.org/r/[email protected]
PS, Ubunt 20.04’s 5.13.0-1026-azure is not affected.
After some discussion it was decided that the revert is the best
solution.
[Test Case]
strace date 2>&1 | grep time
also Microsoft tested
[Where things could go wrong]
vDSO entry point could stop working altogether
[Other Info]
SF: #00338309
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/1977753/+subscriptions
--
Mailing list: https://launchpad.net/~kernel-packages
Post to : [email protected]
Unsubscribe : https://launchpad.net/~kernel-packages
More help : https://help.launchpad.net/ListHelp
