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Message-ID: <20160420185648.5982deb7@arm.com>
Date: Wed, 20 Apr 2016 18:56:48 +0100
From: Marc Zyngier <marc.zyngier@....com>
To: Eric Auger <eric.auger@...aro.org>
Cc: eric.auger@...com, robin.murphy@....com,
alex.williamson@...hat.com, will.deacon@....com, joro@...tes.org,
tglx@...utronix.de, jason@...edaemon.net,
christoffer.dall@...aro.org, linux-arm-kernel@...ts.infradead.org,
patches@...aro.org, linux-kernel@...r.kernel.org,
Bharat.Bhushan@...escale.com, pranav.sawargaonkar@...il.com,
p.fedin@...sung.com, iommu@...ts.linux-foundation.org,
Jean-Philippe.Brucker@....com, julien.grall@....com
Subject: Re: [PATCH v7 6/8] irqchip/gicv2m: implement msi_doorbell_info
callback
On Wed, 20 Apr 2016 14:33:17 +0200
Eric Auger <eric.auger@...aro.org> wrote:
> Marc,
> On 04/20/2016 11:27 AM, Marc Zyngier wrote:
> > On 19/04/16 18:13, Eric Auger wrote:
> >> This patch implements the msi_doorbell_info callback in the
> >> gicv2m driver.
> >>
> >> The driver now is able to return its doorbell characteristics
> >> (base, size, prot). A single doorbell is exposed.
> >>
> >> This will allow the msi layer to iommu_map this doorbell when
> >> requested.
> >>
> >> Signed-off-by: Eric Auger <eric.auger@...aro.org>
> >>
> >> ---
> >>
> >> v7: creation
> >> ---
> >> drivers/irqchip/irq-gic-v2m.c | 32 +++++++++++++++++++++++++++++++-
> >> 1 file changed, 31 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/irqchip/irq-gic-v2m.c b/drivers/irqchip/irq-gic-v2m.c
> >> index 28f047c..54690b9 100644
> >> --- a/drivers/irqchip/irq-gic-v2m.c
> >> +++ b/drivers/irqchip/irq-gic-v2m.c
> >> @@ -24,6 +24,8 @@
> >> #include <linux/of_pci.h>
> >> #include <linux/slab.h>
> >> #include <linux/spinlock.h>
> >> +#include <linux/percpu.h>
> >> +#include <linux/iommu.h>
> >>
> >> /*
> >> * MSI_TYPER:
> >> @@ -64,6 +66,7 @@ struct v2m_data {
> >> u32 nr_spis; /* The number of SPIs for MSIs */
> >> unsigned long *bm; /* MSI vector bitmap */
> >> u32 flags; /* v2m flags for specific implementation */
> >> + struct irq_chip_msi_doorbell_info doorbell_info;
> >> };
> >>
> >> static void gicv2m_mask_msi_irq(struct irq_data *d)
> >> @@ -105,6 +108,16 @@ static void gicv2m_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
> >> msg->data -= v2m->spi_start;
> >> }
> >>
> >> +static const struct irq_chip_msi_doorbell_info *
> >> +gicv2m_msi_doorbell_info(struct irq_data *data)
> >> +{
> >> + struct v2m_data *v2m = irq_data_get_irq_chip_data(data);
> >> +
> >> + if (!v2m)
> >> + return NULL;
> >
> > How can this ever be NULL? I think you can drop that test.
> OK
> >
> >> + return (const struct irq_chip_msi_doorbell_info *)(&v2m->doorbell_info);
> >
> > Please don't do that. Use "const" in the functions that are using
> > irq_chip_msi_doorbell_info, but do not make this "const" here.
> It definitively compiles without casting so obviously this is not needed
> but is there any other wrong thing I don't see?
> we still want this function to return a pointer to a const?
I don't think we can return a const pointer, because it is obviously
not (the memory has been kmalloc'ed, and you've written to it, so it is
not really "read-only").
Maybe I'm being overly zealous, but I've seen compilers taking amazing
shortcuts when offered a const qualifier...
> >
> >> +}
> >> +
> >> static struct irq_chip gicv2m_irq_chip = {
> >> .name = "GICv2m",
> >> .irq_mask = irq_chip_mask_parent,
> >> @@ -112,6 +125,7 @@ static struct irq_chip gicv2m_irq_chip = {
> >> .irq_eoi = irq_chip_eoi_parent,
> >> .irq_set_affinity = irq_chip_set_affinity_parent,
> >> .irq_compose_msi_msg = gicv2m_compose_msi_msg,
> >> + .msi_doorbell_info = gicv2m_msi_doorbell_info,
> >> };
> >>
> >> static int gicv2m_irq_gic_domain_alloc(struct irq_domain *domain,
> >> @@ -247,6 +261,7 @@ static void gicv2m_teardown(void)
> >>
> >> list_for_each_entry_safe(v2m, tmp, &v2m_nodes, entry) {
> >> list_del(&v2m->entry);
> >> + free_percpu(v2m->doorbell_info.percpu_doorbells);
> >> kfree(v2m->bm);
> >> iounmap(v2m->base);
> >> of_node_put(to_of_node(v2m->fwnode));
> >> @@ -299,6 +314,7 @@ static int __init gicv2m_init_one(struct fwnode_handle *fwnode,
> >> {
> >> int ret;
> >> struct v2m_data *v2m;
> >> + struct irq_chip_msi_doorbell __percpu *doorbell;
> >>
> >> v2m = kzalloc(sizeof(struct v2m_data), GFP_KERNEL);
> >> if (!v2m) {
> >> @@ -311,11 +327,23 @@ static int __init gicv2m_init_one(struct fwnode_handle *fwnode,
> >>
> >> memcpy(&v2m->res, res, sizeof(struct resource));
> >>
> >> + v2m->doorbell_info.percpu_doorbells =
> >> + alloc_percpu(struct irq_chip_msi_doorbell);
> >> + if (WARN_ON(!v2m->doorbell_info.percpu_doorbells)) {
> >> + ret = -ENOMEM;
> >> + goto err_free_v2m;
> >> + }
> >> + doorbell = per_cpu_ptr(v2m->doorbell_info.percpu_doorbells, 0);
> >> + doorbell->base = v2m->res.start;
> >> + doorbell->size = 4;
> >> + doorbell->prot = IOMMU_WRITE;
> >
> > You probably need to also have something that says IOMMU_DEVICE or
> > something similar, because I'm afraid you're getting a memory mapping
> > here. I've had a quick look at the two other series, but couldn't find
> > anything that would force the memory attributes.
> Yes you're right I currently just enforce the direction (which is
> checked against what VFIO user registered). Do you refer to IOMMU_MMIO,
> latterly proposed on the ML. In the positive, yes I intend to add it
> once it gets upstreamed.
Yeah, Robin's patches should become a dependency here, because there is
absolutely no guarantee that the device write to the doorbell won't be
treated a normal cacheable memory, with disastrous effects.
Thanks,
M.
--
Jazz is not dead. It just smells funny.
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