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Message-ID: <20110404171739.GA15070@dumpdata.com>
Date: Mon, 4 Apr 2011 13:17:39 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc: "xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Jeremy Fitzhardinge <Jeremy.Fitzhardinge@...rix.com>
Subject: Re: [PATCH] xen: do not clear and mask evtchns in
__xen_evtchn_do_upcall
> I reworded this part of the commit message, see below updated patch.
>
[looking]
.. snip..
> > Can you expand? As in for the GSI? Or for the MSI/MSI-X?
>
> Linux on native would use handle_edge_irq for edge irqs and msis, and
> handle_fasteoi_irq for everything else.
What about per_cpu one?
.. snip ..
> >
> > OK. You need a big comment about this in the code. Explain
> > why this is happening. B/c if you look at this from code
> > it seems like wrong thing to do for gsi's (as in you would
> > think handle_level_irq would the right choice).
>
> Except handle_level_irq is not used anymore anywhere in the kernel, give
> a look at arch/x86/kernel/apic/io_apic.c:ioapic_register_intr.
'make_8259A_irq' ? But yeah, I don't think we will hit machines with
that architecture anymore.
>
> Updated patch, rebased on 2.6.39-rc1 follows:
>
> ---
>
>
> commit 6978531913b45abf3aff048475a2174a2cdaf288
> Author: Stefano Stabellini <stefano.stabellini@...citrix.com>
> Date: Tue Mar 29 14:15:06 2011 +0000
>
> xen: do not clear and mask evtchns in __xen_evtchn_do_upcall
>
> Change the irq handler of virqs and pirqs that don't need EOI (pirqs
> that correspond to physical edge interrupts) to handle_edge_irq.
>
> Use handle_fasteoi_irq for pirqs that need eoi (they generally
> correspond to level triggered irqs), no risk in loosing interrupts
> because we have to EOI the irq anyway.
>
> This change has the following benefits:
>
> - it uses the very same handlers that Linux would use on native for the
> same irqs (handle_edge_irq for edge irqs and msis, and
^^^-'MSIs/MSI-Xs'
> handle_fasteoi_irq for everything else);
>
> - it uses these handlers in the same way Linux would use them: it let
^- 's'
> Linux mask\unmask and ack the irq when Linux want to mask\unmask and ack
^- 's'
> the irq;
>
> See genericirq in the kernel docbook docs for more informations.
Say 'Documentation/DocBook/genericirq.tmpl'
[edit: The patch looks OK to me, but let me think about this some more over this
week and sketch out the flow].
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
>
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index 036343b..186eb1e 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -118,6 +118,8 @@ static DEFINE_PER_CPU(unsigned long [NR_EVENT_CHANNELS/BITS_PER_LONG],
> static struct irq_chip xen_dynamic_chip;
> static struct irq_chip xen_percpu_chip;
> static struct irq_chip xen_pirq_chip;
> +static void enable_dynirq(struct irq_data *data);
> +static void disable_dynirq(struct irq_data *data);
>
> /* Get info for IRQ */
> static struct irq_info *info_for_irq(unsigned irq)
> @@ -473,16 +475,6 @@ static void xen_free_irq(unsigned irq)
> irq_free_desc(irq);
> }
>
> -static void pirq_unmask_notify(int irq)
> -{
> - struct physdev_eoi eoi = { .irq = pirq_from_irq(irq) };
> -
> - if (unlikely(pirq_needs_eoi(irq))) {
> - int rc = HYPERVISOR_physdev_op(PHYSDEVOP_eoi, &eoi);
> - WARN_ON(rc);
> - }
> -}
> -
> static void pirq_query_unmask(int irq)
> {
> struct physdev_irq_status_query irq_status;
> @@ -506,6 +498,29 @@ static bool probing_irq(int irq)
> return desc && desc->action == NULL;
> }
>
> +static void eoi_pirq(struct irq_data *data)
> +{
> + int evtchn = evtchn_from_irq(data->irq);
> + struct physdev_eoi eoi = { .irq = pirq_from_irq(data->irq) };
> + int rc = 0;
> +
> + irq_move_irq(data);
> +
> + if (VALID_EVTCHN(evtchn))
> + clear_evtchn(evtchn);
> +
> + if (pirq_needs_eoi(data->irq)) {
> + rc = HYPERVISOR_physdev_op(PHYSDEVOP_eoi, &eoi);
> + WARN_ON(rc);
> + }
> +}
> +
> +static void mask_ack_pirq(struct irq_data *data)
> +{
> + disable_dynirq(data);
> + eoi_pirq(data);
> +}
> +
> static unsigned int __startup_pirq(unsigned int irq)
> {
> struct evtchn_bind_pirq bind_pirq;
> @@ -539,7 +554,7 @@ static unsigned int __startup_pirq(unsigned int irq)
>
> out:
> unmask_evtchn(evtchn);
> - pirq_unmask_notify(irq);
> + eoi_pirq(irq_get_irq_data(irq));
>
> return 0;
> }
> @@ -572,27 +587,6 @@ static void shutdown_pirq(struct irq_data *data)
> info->evtchn = 0;
> }
>
> -static void enable_pirq(struct irq_data *data)
> -{
> - startup_pirq(data);
> -}
> -
> -static void disable_pirq(struct irq_data *data)
> -{
> -}
> -
> -static void ack_pirq(struct irq_data *data)
> -{
> - int evtchn = evtchn_from_irq(data->irq);
> -
> - irq_move_irq(data);
> -
> - if (VALID_EVTCHN(evtchn)) {
> - mask_evtchn(evtchn);
> - clear_evtchn(evtchn);
> - }
> -}
> -
> static int find_irq_by_gsi(unsigned gsi)
> {
> struct irq_info *info;
> @@ -639,9 +633,6 @@ int xen_bind_pirq_gsi_to_irq(unsigned gsi,
> if (irq < 0)
> goto out;
>
> - irq_set_chip_and_handler_name(irq, &xen_pirq_chip, handle_level_irq,
> - name);
> -
> irq_op.irq = irq;
> irq_op.vector = 0;
>
> @@ -658,6 +649,19 @@ int xen_bind_pirq_gsi_to_irq(unsigned gsi,
> xen_irq_info_pirq_init(irq, 0, pirq, gsi, irq_op.vector,
> shareable ? PIRQ_SHAREABLE : 0);
>
> + pirq_query_unmask(irq);
> + /* we try to follow the same convention as Linux on native:
> + * handle_edge_irq for edge irqs and handle_fasteoi_irq for level
> + * irqs, see ioapic_register_intr (handle_level_irq is not used
> + * anymore).
> + */
> + if (pirq_needs_eoi(irq))
> + irq_set_chip_and_handler_name(irq, &xen_pirq_chip,
> + handle_fasteoi_irq, name);
> + else
> + irq_set_chip_and_handler_name(irq, &xen_pirq_chip,
> + handle_edge_irq, name);
> +
> out:
> spin_unlock(&irq_mapping_update_lock);
>
> @@ -690,8 +694,8 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct msi_desc *msidesc,
> if (irq == -1)
> goto out;
>
> - irq_set_chip_and_handler_name(irq, &xen_pirq_chip, handle_level_irq,
> - name);
> + irq_set_chip_and_handler_name(irq, &xen_pirq_chip, handle_edge_irq,
> + name);
>
> xen_irq_info_pirq_init(irq, 0, pirq, 0, vector, 0);
> ret = irq_set_msi_desc(irq, msidesc);
> @@ -773,7 +777,7 @@ int bind_evtchn_to_irq(unsigned int evtchn)
> goto out;
>
> irq_set_chip_and_handler_name(irq, &xen_dynamic_chip,
> - handle_fasteoi_irq, "event");
> + handle_edge_irq, "event");
>
> xen_irq_info_evtchn_init(irq, evtchn);
> }
> @@ -1181,9 +1185,6 @@ static void __xen_evtchn_do_upcall(void)
> port = (word_idx * BITS_PER_LONG) + bit_idx;
> irq = evtchn_to_irq[port];
>
> - mask_evtchn(port);
> - clear_evtchn(port);
> -
> if (irq != -1) {
> desc = irq_to_desc(irq);
> if (desc)
> @@ -1339,12 +1340,18 @@ static void ack_dynirq(struct irq_data *data)
> {
> int evtchn = evtchn_from_irq(data->irq);
>
> - irq_move_masked_irq(data);
> + irq_move_irq(data);
>
> if (VALID_EVTCHN(evtchn))
> - unmask_evtchn(evtchn);
> + clear_evtchn(evtchn);
> }
>
> +static void mask_ack_dynirq(struct irq_data *data)
> +{
> + disable_dynirq(data);
> + ack_dynirq(data);
> +}
> +
> static int retrigger_dynirq(struct irq_data *data)
> {
> int evtchn = evtchn_from_irq(data->irq);
> @@ -1533,11 +1540,12 @@ void xen_irq_resume(void)
> static struct irq_chip xen_dynamic_chip __read_mostly = {
> .name = "xen-dyn",
>
> - .irq_disable = disable_dynirq,
> .irq_mask = disable_dynirq,
> .irq_unmask = enable_dynirq,
>
> - .irq_eoi = ack_dynirq,
> + .irq_ack = ack_dynirq,
> + .irq_mask_ack = mask_ack_dynirq,
> +
> .irq_set_affinity = set_affinity_irq,
> .irq_retrigger = retrigger_dynirq,
> };
> @@ -1548,13 +1556,12 @@ static struct irq_chip xen_pirq_chip __read_mostly = {
> .irq_startup = startup_pirq,
> .irq_shutdown = shutdown_pirq,
>
> - .irq_enable = enable_pirq,
> - .irq_unmask = enable_pirq,
> -
> - .irq_disable = disable_pirq,
> - .irq_mask = disable_pirq,
> + .irq_mask = disable_dynirq,
> + .irq_unmask = enable_dynirq,
>
> - .irq_ack = ack_pirq,
> + .irq_ack = eoi_pirq,
> + .irq_eoi = eoi_pirq,
> + .irq_mask_ack = mask_ack_pirq,
>
> .irq_set_affinity = set_affinity_irq,
>
--
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