On 05/06/2013 09:43:37 PM, tiejun.chen wrote:
On 05/07/2013 10:06 AM, Scott Wood wrote:
On 05/06/2013 08:56:25 PM, tiejun.chen wrote:
On 05/07/2013 07:50 AM, Scott Wood wrote:
On 05/05/2013 10:13:17 PM, tiejun.chen wrote:
On 05/06/2013 11:10 AM, Tiejun Chen wrote:
For the external interrupt, the decrementer exception and the
doorbell
excpetion, we also need to soft-disable interrupts while doing
as host
interrupt handlers since the DO_KVM hook is always performed to
skip
EXCEPTION_COMMON then miss this original chance with the 'ints'
(INTS_DISABLE).
http://patchwork.ozlabs.org/patch/241344/
http://patchwork.ozlabs.org/patch/241412/
:-)
I'm observing the same behaviour as well:
WARN_ON_ONCE(!irqs_disabled());
So, could you explain the benefits of your approach over what's
being discussed
in those threads?
They're a long thread so I think I need to take time to see :)
Why wouldn't we always disable them? kvmppc_handle_exit() will
enable
interrupts when it's ready.
This only disable soft interrupt for kvmppc_restart_interrupt()
that restarts
interrupts if they were meant for the host:
a. SOFT_DISABLE_INTS() only for BOOKE_INTERRUPT_EXTERNAL |
BOOKE_INTERRUPT_DECREMENTER | BOOKE_INTERRUPT_DOORBELL
Those aren't the only exceptions that can end up going to the host.
We could
get a TLB miss that results in a heavyweight MMIO exit, etc.
This is like host handler, so I'm just disabling soft interrupt
during kvmppc_restart_interrupt() for Doorbell interrupt/Decrementer
Interrupt/External Input Interrupt.
I don't see anything should be disabled for any TLB exception in host
handler.
Every exception type needs consistent lazy EE state once we hit the
local_irq_enable() (or any other C code that cares).
Plus, if you're going to add code to make something conditional, you
should have a good reason for making it conditional. Being more like
the 64-bit host handler for its own sake isn't good enough, especially
if you introduce differences between 32 and 64 bit in the process.
And I'd rather see any fix for this problem stay out of the asm code.
We already have an appropriate SOFT_DISABLE_INTS so I think we can
take this easily :)
An unconditional call to hard_irq_disable() at the beginning of
kvmppc_handle_exit() should suffice. I already have this in the next
version of my patch that I'll be posting shortly.
Note that we need this on 32-bit as well, so that trace_hardirqs_off()
gets called.
-Scott
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