On 05/09/2013 04:23 PM, Bhushan Bharat-R65777 wrote:
-----Original Message-----
From: Linuxppc-dev [mailto:linuxppc-dev-
bounces+bharat.bhushan=freescale....@lists.ozlabs.org] On Behalf Of Caraman
Mihai Claudiu-B02008
Sent: Wednesday, May 08, 2013 6:44 PM
To: Wood Scott-B07421; tiejun.chen
Cc: linuxppc-...@lists.ozlabs.org; ag...@suse.de; kvm-ppc@vger.kernel.org;
k...@vger.kernel.org
Subject: RE: [RFC][KVM][PATCH 1/1] kvm:ppc:booke-64: soft-disable interrupts
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 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?
I think Tiejun was saying that host has flags and replays only EE/DEC/DBELL
interrupts. There is special macro masked_interrupt_book3e in those exception
handlers that sets paca->irq_happened.
The list of replied interrupts is limited to asynchronous noncritical interrupts
which can be masked by MSR[EE] (therefore no TLB miss). Now on KVM book3e we
don't want to put them in the irq_happened lazy state but rather to execute them
directly, so there is no reason for exception handling symmetry between host and
guest.
Another Question:
The case is:
Actually in the case GS=1 even if EE=0, EXT/DEC/DBELL still occur as I recall.
Case 1)
-> Local_irq_disable() will set soft_enabled = 0
-> Now Externel interrupt happens, there we set PACA_IRQ_EE in irq_happened,
Also clears EE in SRR1 and rfi. So interrupts are hard disabled. No more other
interrupt gated by MSR.EE can happen. Looks like the idea here is to not let a
device keep on inserting interrupt till the interrupt condition on device is
cleared, right?
I don't understand "the interrupt condition on device is cleared" here.
I think regardless if you clear the device interrupt status, the system still
receive a pending interrupt once EE or GS = 1.
-> local_irq_enable() - This checks that irq_happened is set, and replays
ret_from_except also check to replay.
Now the case 2)
Case 2)
-> Local_irq_disable() will set soft_enabled = 0
-> Now DEC interrupt happens. We set PACA_IRQ_DEC in irq_happened, But do not
clear EE in SRR1 and rfi. So interrupts are not hard disabled.
-> Now say EE interrupt happens, there we set PACA_IRQ_EE in irq_happened,
Also clears EE in SRR1 and rfi. So interrupts are hard disabled.
-> local_irq_enable() - This checks that irq_happened is set.
IIUC, it replays only one interrupt? is not it?
After anyone is replayed in arch_local_irq_restore(), we will set soft/hard
interrupt there:
set_soft_enabled(1);
__hard_irq_enable();
Then any pending interrupt can be executed now.
Additionally, ret_from_except probably check to replay all.
Tiejun
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