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Message-ID: <572A13AB.6000208@linaro.org>
Date: Wed, 4 May 2016 17:22:19 +0200
From: Eric Auger <eric.auger@...aro.org>
To: Marc Zyngier <marc.zyngier@....com>, 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
Cc: 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 v8 7/8] genirq/msi: map/unmap the MSI doorbells on
msi_domain_alloc/free_irqs
Hi Marc,
On 05/04/2016 03:21 PM, Marc Zyngier wrote:
> On 28/04/16 09:22, Eric Auger wrote:
>> This patch handles the iommu mapping of MSI doorbells that require to
>> be mapped in an iommu domain. This happens on msi_domain_alloc/free_irqs
>> since this is called in code that can sleep (pci_enable/disable_msi):
>> iommu_map/unmap is not stated as atomic. On msi_domain_(de)activate and
>> msi_domain_set_affinity, which must be atomic, we just lookup for this
>> pre-allocated/mapped IOVA.
>>
>> Signed-off-by: Eric Auger <eric.auger@...aro.org>
>>
>> ---
>> v7 -> v8:
>> - new percpu pointer type
>> - exit from the irq domain hierarchy parsing on first map/unmap success
>> - reset desc->irq to 0 on mapping failure
>>
>> v7: creation
>> ---
>> kernel/irq/msi.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++------
>> 1 file changed, 79 insertions(+), 8 deletions(-)
>>
>> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
>> index 72bf4d6..d5f95e6 100644
>> --- a/kernel/irq/msi.c
>> +++ b/kernel/irq/msi.c
>> @@ -14,6 +14,8 @@
>> #include <linux/irq.h>
>> #include <linux/irqdomain.h>
>> #include <linux/msi.h>
>> +#include <linux/msi-iommu.h>
>> +#include <linux/iommu.h>
>>
>> /* Temparory solution for building, will be removed later */
>> #include <linux/pci.h>
>> @@ -322,6 +324,56 @@ int msi_domain_populate_irqs(struct irq_domain *domain, struct device *dev,
>> }
>>
>> /**
>> + * msi_handle_doorbell_mappings: in case the irq data corresponds to an
>> + * MSI that requires iommu mapping, traverse the irq domain hierarchy
>> + * to retrieve the doorbells to handle and iommu_map/unmap them according
>> + * to @map boolean.
>> + *
>> + * @data: irq data handle
>> + * @map: mapping if true, unmapping if false
>> + */
>> +static int msi_handle_doorbell_mappings(struct irq_data *data, bool map)
>> +{
>> + for (; data; data = data->parent_data) {
>> + struct device *dev =
>> + msi_desc_to_dev(irq_data_get_msi_desc(data));
>> + struct irq_chip *chip = irq_data_get_irq_chip(data);
>> + const struct irq_chip_msi_doorbell_info *dbinfo;
>> + struct iommu_domain *domain;
>> + phys_addr_t __percpu *db_addr;
>> + dma_addr_t iova;
>> + int ret = 0, i;
>> +
>> + domain = iommu_msi_domain(dev);
>> + if (!domain)
>> + continue;
>> +
>> + if (!chip->msi_doorbell_info)
>> + continue;
>> +
>> + dbinfo = chip->msi_doorbell_info(data);
>> + if (!dbinfo)
>> + return -EINVAL;
>> +
>> + for (i = 0; i < dbinfo->nb_doorbells; i++) {
>> + db_addr = per_cpu_ptr(dbinfo->percpu_doorbells, i);
>> + if (map) {
>> + ret = iommu_msi_get_doorbell_iova(domain,
>> + *db_addr,
>> + dbinfo->size,
>> + dbinfo->prot,
>> + &iova);
>> + if (ret)
>> + return ret;
>> + } else
>> + iommu_msi_put_doorbell_iova(domain, *db_addr);
>> + }
>> + break;
>> + }
>> + return 0;
>> +}
>
> I'm really not fond of this whole loop. Could you try to decouple the
> irq_data parsing (looking for a msi_doorbell_info method) from the
> actual mapping/unmapping? This would make it a lot more readable.
> Something along the lines of:
Just sent v9 where I addressed all your comments. Please let me know
whether this looks better.
>
> struct device *dev;
> struct irq_chip *chip;
> struct iommu_domain *domain;
> const struct irq_chip_msi_doorbell_info *dbinfo;
>
> while (data) {
> dev = msi_desc_to_dev(irq_data_get_msi_desc(data));
> domain = iommu_msi_domain(dev);
> if (!domain)
> continue;
>
> chip = irq_data_get_irq_chip(data);
> if (chip->msi_doorbell_info)
> break;
>
> data = data->parent;
> }
>
> if (!data)
> return 0;
>
> dbinfo = chip->msi_doorbell_info(data);
> if (!dbinfo)
> return -EINVAL;
>
> [... handle mapping/unmapping here ...]
>
>> +
>> +/**
>> * msi_domain_alloc_irqs - Allocate interrupts from a MSI interrupt domain
>> * @domain: The domain to allocate from
>> * @dev: Pointer to device struct of the device for which the interrupts
>> @@ -352,17 +404,26 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
>>
>> virq = __irq_domain_alloc_irqs(domain, virq, desc->nvec_used,
>> dev_to_node(dev), &arg, false);
>> - if (virq < 0) {
>> - ret = -ENOSPC;
>> - if (ops->handle_error)
>> - ret = ops->handle_error(domain, desc, ret);
>> - if (ops->msi_finish)
>> - ops->msi_finish(&arg, ret);
>> - return ret;
>> - }
>> + if (virq < 0)
>> + goto error;
>>
>> for (i = 0; i < desc->nvec_used; i++)
>> irq_set_msi_desc_off(virq, i, desc);
>> +
>> + for (i = 0; i < desc->nvec_used; i++) {
>> + ret = msi_handle_doorbell_mappings(
>> + irq_get_irq_data(virq + i), true);
>
> Do not be afraid of longer lines. Or if you are, create an intermediate
> variable. But this kind of construct makes my brain work harder, and I
> hate the feeling... ;-)
Yes I am afraid of checkpatch and I do my utmost to abide by its law ;-)
Well, let me know if the v9 is of any relief for your brain ;-)
Thanks for your time!
Eric
>
>> + if (ret)
>> + break;
>> + }
>> + if (ret) {
>> + for (; i >= 0; i--)
>> + msi_handle_doorbell_mappings(
>> + irq_get_irq_data(virq + i), false);
>> + irq_domain_free_irqs(virq, desc->nvec_used);
>> + desc->irq = 0;
>> + goto error;
>> + }
>> }
>>
>> if (ops->msi_finish)
>> @@ -377,6 +438,13 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
>> }
>>
>> return 0;
>> +error:
>> + ret = -ENOSPC;
>> + if (ops->handle_error)
>> + ret = ops->handle_error(domain, desc, ret);
>> + if (ops->msi_finish)
>> + ops->msi_finish(&arg, ret);
>> + return ret;
>> }
>>
>> /**
>> @@ -396,6 +464,9 @@ void msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
>> * entry. If that's the case, don't do anything.
>> */
>> if (desc->irq) {
>> + msi_handle_doorbell_mappings(
>> + irq_get_irq_data(desc->irq),
>> + false);
>> irq_domain_free_irqs(desc->irq, desc->nvec_used);
>> desc->irq = 0;
>> }
>>
>
> Thanks,
>
> M.
>
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