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?
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.
And I'd rather see any fix for this problem stay out of the asm code.
b. bl kvmppc_handle_exit
c. kvmppc_handle_exit()
{
int r = RESUME_HOST;
int s;
/* update before a new last_exit_type is rewritten */
kvmppc_update_timing_stats(vcpu);
/* restart interrupts if they were meant for the host */
kvmppc_restart_interrupt(vcpu, exit_nr);
local_irq_enable(); ==> Enable again.
....
And shouldn't we handle kvmppc_restart_interrupt() like the original
HOST flow?
#define MASKABLE_EXCEPTION(trapnum, intnum, label, hdlr,
ack) \
START_EXCEPTION(label); \
NORMAL_EXCEPTION_PROLOG(trapnum, intnum,
PROLOG_ADDITION_MASKABLE)\
EXCEPTION_COMMON(trapnum, PACA_EXGEN,
*INTS_DISABLE*) \
...
Could you elaborate on what you mean?
-Scott
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