** Description changed:
[Impact]
- cntvct_el0 could be left untrapped if reset with the user access bit set
+ This bug captures a few issues with the ARM arch_timer driver:
+
+ 1) Some arm64 systems have hardware defects in their architected timer
+ implementations that require errata, which we workaround in the kernel.
+ However, it's possible that this workaround will not be applied if the
+ timer was reset w/ the user access bit set.
+
+ 2) The Juno board fails to initialize a timer at boot:
+
+ arch_timer: Unable to map frame @ 0x0000000000000000
+ arch_timer: Frame missing phys irq.
+ Failed to initialize '/timer@2a810000': -22
+
+ 3) Possible boot warning from arch_timer_mem_of_init():
+ 'Trying to vfree() nonexistent vm area'
+
+ 4) There's a theoretical problem where the first frame of a timer could
+ be used even though a better suited timer frame is available.
+
+ 5) An infinite recursion loop will occur when enabling the function
+ tracer in builds with CONFIG_PREEMPT_TRACER=y. Ubuntu does not enable
+ CONFIG_PREEMPT_TRACER, so this will only be a problem if that changes.
[Test Case]
+
[Regression Risk]
** Changed in: linux (Ubuntu)
Status: Incomplete => Confirmed
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https://bugs.launchpad.net/bugs/1713821
Title:
arm64 arch_timer fixes
Status in linux package in Ubuntu:
Confirmed
Status in linux source package in Zesty:
Confirmed
Bug description:
[Impact]
This bug captures a few issues with the ARM arch_timer driver:
1) Some arm64 systems have hardware defects in their architected timer
implementations that require errata, which we workaround in the
kernel. However, it's possible that this workaround will not be
applied if the timer was reset w/ the user access bit set.
2) The Juno board fails to initialize a timer at boot:
arch_timer: Unable to map frame @ 0x0000000000000000
arch_timer: Frame missing phys irq.
Failed to initialize '/timer@2a810000': -22
3) Possible boot warning from arch_timer_mem_of_init():
'Trying to vfree() nonexistent vm area'
4) There's a theoretical problem where the first frame of a timer
could be used even though a better suited timer frame is available.
5) An infinite recursion loop will occur when enabling the function
tracer in builds with CONFIG_PREEMPT_TRACER=y. Ubuntu does not enable
CONFIG_PREEMPT_TRACER, so this will only be a problem if that changes.
[Test Case]
[Regression Risk]
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