From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Paul Mackerras <paulus@ozlabs.org>
Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org
Subject: Re: [PATCH v2 08/11] powerpc/kvm/xive: Keep escalation interrupt masked unless ceded
Date: Mon, 27 Nov 2017 08:55:48 +1100 [thread overview]
Message-ID: <1511733348.2466.63.camel@kernel.crashing.org> (raw)
In-Reply-To: <20171125045634.GA10920@fergus.ozlabs.ibm.com>
On Sat, 2017-11-25 at 15:56 +1100, Paul Mackerras wrote:
> On Thu, Nov 23, 2017 at 03:36:16PM +1100, Benjamin Herrenschmidt wrote:
> > This works on top of the single escalation support. When in single
> > escalation, with this change, we will keep the escalation interrupt
> > disabled unless the VCPU is in H_CEDE (idle). In any other case, we
> > know the VCPU will be rescheduled and thus there is no need to take
> > escalation interrupts in the host whenever a guest interrupt fires.
>
> Some comments below...
>
> > @@ -2705,7 +2740,32 @@ kvm_cede_prodded:
> > /* we've ceded but we want to give control to the host */
> > kvm_cede_exit:
> > ld r9, HSTATE_KVM_VCPU(r13)
> > - b guest_exit_cont
> > +#ifdef CONFIG_KVM_XICS
> > + /* Abort if we still have a pending escalation */
>
> This comment might be clearer if you say "Cancel cede" rather than
> "Abort".
>
> > diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
> > index eef9ccafdc09..7a047bc88f11 100644
> > --- a/arch/powerpc/kvm/book3s_xive.c
> > +++ b/arch/powerpc/kvm/book3s_xive.c
> > @@ -89,6 +89,17 @@ static irqreturn_t xive_esc_irq(int irq, void *data)
> > if (vcpu->arch.ceded)
> > kvmppc_fast_vcpu_kick(vcpu);
> >
> > + /* Since we have the no-EOI flag, the interrupt is effectively
> > + * disabled now. Clearing xive_esc_on means we won't bother
> > + * doing so on the next entry.
> > + *
> > + * This also allows the entry code to know that if a PQ combination
> > + * of 10 is observed while xive_esc_on is true, it means the queue
> > + * contains an unprocessed escalation interrupt. We don't make use of
> > + * that knowledge today but might (see comment in book3s_hv_rmhandler.S)
>
> Is "We don't make use of that knowledge" actually true? I thought we
> did make use of it in the assembly code in book3s_hv_rmhandlers.S (in
> the code that this patch adds). In what way don't we make use of it?
Obsolete comment, sorry.
Cheers,
Ben.
next prev parent reply other threads:[~2017-11-26 21:55 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-23 4:36 [PATCH v2 01/11] powerpc/kvm/xive: Add more debugfs queues info Benjamin Herrenschmidt
2017-11-23 4:36 ` [PATCH v2 02/11] powerpc/kvm/xive: Enable use of the new "single escalation" feature Benjamin Herrenschmidt
2017-11-23 4:36 ` [PATCH v2 03/11] powerpc/kvm/xive: Don't use existing "prodded" flag for xive escalations Benjamin Herrenschmidt
2017-11-23 4:36 ` [PATCH v2 04/11] powerpc/kvm/xive: Check DR not IR to chose real vs virt mode MMIOs Benjamin Herrenschmidt
2017-11-23 4:36 ` [PATCH v2 05/11] powerpc/kvm/xive: Make xive_pushed a byte, not a word Benjamin Herrenschmidt
2017-11-23 4:36 ` [PATCH v2 06/11] powerpc/xive: Move definition of ESB bits Benjamin Herrenschmidt
2017-11-23 4:36 ` [PATCH v2 07/11] powerpc/xive: Add interrupt flag to disable automatic EOI Benjamin Herrenschmidt
2017-11-23 4:36 ` [PATCH v2 08/11] powerpc/kvm/xive: Keep escalation interrupt masked unless ceded Benjamin Herrenschmidt
2017-11-25 4:56 ` Paul Mackerras
2017-11-26 21:55 ` Benjamin Herrenschmidt [this message]
2017-11-23 4:36 ` [PATCH v2 09/11] powerpc/kvm: Make "no_xive:" label local Benjamin Herrenschmidt
2017-11-23 4:36 ` [PATCH v2 10/11] powerpc/kvm: Store the MMU mode in the PACA on KVM exit Benjamin Herrenschmidt
2017-11-24 15:15 ` kbuild test robot
2017-11-25 5:03 ` Paul Mackerras
2017-11-26 21:57 ` Benjamin Herrenschmidt
2017-11-23 4:36 ` [PATCH v2 11/11] powerpc/kvm: Use the PACA virt/real mode info instead of mfmsr Benjamin Herrenschmidt
2017-11-25 5:17 ` Paul Mackerras
2017-11-26 21:58 ` Benjamin Herrenschmidt
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