Re: [RFC v3 15/15] irqchip/gicv2m/v3-its-pci-msi: IOMMU map the MSI frame when needed

[Eric Auger]

Hi Marc,
On 02/18/2016 12:33 PM, Marc Zyngier wrote:
> On Fri, 12 Feb 2016 08:13:17 +0000
> Eric Auger <eric.auger@xxxxxxxxxx> wrote:
> 
>> In case the msi_desc references a device attached to an iommu
>> domain, the msi address needs to be mapped in the IOMMU. Else any
>> MSI write transaction will cause a fault.
>>
>> gic_set_msi_addr detects that case and allocates an iova bound
>> to the physical address page comprising the MSI frame. This iova
>> then is used as the msi_msg address. Unset operation decrements the
>> reference on the binding.
>>
>> The functions are called in the irq_write_msi_msg ops implementation.
>> At that time we can recognize whether the msi is setup or teared down
>> looking at the msi_msg content. Indeed msi_domain_deactivate zeroes all
>> the fields.
>>
>> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
>>
>> ---
>>
>> v2 -> v3:
>> - protect iova/addr manipulation with CONFIG_ARCH_DMA_ADDR_T_64BIT and
>>   CONFIG_PHYS_ADDR_T_64BIT
>> - only expose gic_pci_msi_domain_write_msg in case CONFIG_IOMMU_API &
>>   CONFIG_PCI_MSI_IRQ_DOMAIN are set.
>> - gic_set/unset_msi_addr duly become static
>> ---
>>  drivers/irqchip/irq-gic-common.c         | 69 ++++++++++++++++++++++++++++++++
>>  drivers/irqchip/irq-gic-common.h         |  5 +++
>>  drivers/irqchip/irq-gic-v2m.c            |  7 +++-
>>  drivers/irqchip/irq-gic-v3-its-pci-msi.c |  5 +++
>>  4 files changed, 85 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/irqchip/irq-gic-common.c b/drivers/irqchip/irq-gic-common.c
>> index f174ce0..46cd06c 100644
>> --- a/drivers/irqchip/irq-gic-common.c
>> +++ b/drivers/irqchip/irq-gic-common.c
>> @@ -18,6 +18,8 @@
>>  #include <linux/io.h>
>>  #include <linux/irq.h>
>>  #include <linux/irqchip/arm-gic.h>
>> +#include <linux/iommu.h>
>> +#include <linux/msi.h>
>>  
>>  #include "irq-gic-common.h"
>>  
>> @@ -121,3 +123,70 @@ void gic_cpu_config(void __iomem *base, void (*sync_access)(void))
>>  	if (sync_access)
>>  		sync_access();
>>  }
>> +
>> +#if defined(CONFIG_IOMMU_API) && defined(CONFIG_PCI_MSI_IRQ_DOMAIN)
>> +static int gic_set_msi_addr(struct irq_data *data, struct msi_msg *msg)
>> +{
>> +	struct msi_desc *desc = irq_data_get_msi_desc(data);
>> +	struct device *dev = msi_desc_to_dev(desc);
>> +	struct iommu_domain *d;
>> +	phys_addr_t addr;
>> +	dma_addr_t iova;
>> +	int ret;
>> +
>> +	d = iommu_get_domain_for_dev(dev);
>> +	if (!d)
>> +		return 0;
>> +#ifdef CONFIG_PHYS_ADDR_T_64BIT
>> +	addr = ((phys_addr_t)(msg->address_hi) << 32) | msg->address_lo;
>> +#else
>> +	addr = msg->address_lo;
>> +#endif
>> +
>> +	ret = iommu_get_single_reserved(d, addr, IOMMU_WRITE, &iova);
>> +
>> +	if (!ret) {
>> +		msg->address_lo = lower_32_bits(iova);
>> +		msg->address_hi = upper_32_bits(iova);
>> +	}
>> +	return ret;
>> +}
>> +
>> +
>> +static void gic_unset_msi_addr(struct irq_data *data)
>> +{
>> +	struct msi_desc *desc = irq_data_get_msi_desc(data);
>> +	struct device *dev;
>> +	struct iommu_domain *d;
>> +	dma_addr_t iova;
>> +
>> +#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
>> +	iova = ((dma_addr_t)(desc->msg.address_hi) << 32) |
>> +		desc->msg.address_lo;
>> +#else
>> +	iova = desc->msg.address_lo;
>> +#endif
>> +
>> +	dev = msi_desc_to_dev(desc);
>> +	if (!dev)
>> +		return;
>> +
>> +	d = iommu_get_domain_for_dev(dev);
>> +	if (!d)
>> +		return;
>> +
>> +	iommu_put_single_reserved(d, iova);
>> +}
>> +
>> +void gic_pci_msi_domain_write_msg(struct irq_data *irq_data,
>> +				  struct msi_msg *msg)
>> +{
>> +	if (!msg->address_hi && !msg->address_lo && !msg->data)
>> +		gic_unset_msi_addr(irq_data); /* deactivate */
>> +	else
>> +		gic_set_msi_addr(irq_data, msg); /* activate, set_affinity */
>> +
>> +	pci_msi_domain_write_msg(irq_data, msg);
>> +}
> 
> So by doing that, you are specializing this infrastructure to PCI.
> If you hijacked irq_compose_msi_msg() instead, you'd have both
> platform and PCI MSI for the same price.
> 
> I can see a potential problem with the teardown of an MSI (I don't
> think the compose method is called on teardown), but I think this could
> be easily addressed.
Yes effectively this is the reason why I moved it from
irq_compose_msi_msg (my original implementation) to irq_write_msi_msg. I
noticed I had no way to detect the teardown whereas the
msi_domain_deactivate also calls irq_write_msi_msg which is quite
practical ;-) To be honest I need to further look at the non PCI
implementation.


> 
>> +#endif
>> +
>> diff --git a/drivers/irqchip/irq-gic-common.h b/drivers/irqchip/irq-gic-common.h
>> index fff697d..98681fd 100644
>> --- a/drivers/irqchip/irq-gic-common.h
>> +++ b/drivers/irqchip/irq-gic-common.h
>> @@ -35,4 +35,9 @@ void gic_cpu_config(void __iomem *base, void (*sync_access)(void));
>>  void gic_enable_quirks(u32 iidr, const struct gic_quirk *quirks,
>>  		void *data);
>>  
>> +#if defined(CONFIG_PCI_MSI_IRQ_DOMAIN) && defined(CONFIG_IOMMU_API)
>> +void gic_pci_msi_domain_write_msg(struct irq_data *irq_data,
>> +				  struct msi_msg *msg);
>> +#endif
>> +
>>  #endif /* _IRQ_GIC_COMMON_H */
>> diff --git a/drivers/irqchip/irq-gic-v2m.c b/drivers/irqchip/irq-gic-v2m.c
>> index c779f83..692d809 100644
>> --- a/drivers/irqchip/irq-gic-v2m.c
>> +++ b/drivers/irqchip/irq-gic-v2m.c
>> @@ -24,6 +24,7 @@
>>  #include <linux/of_pci.h>
>>  #include <linux/slab.h>
>>  #include <linux/spinlock.h>
>> +#include "irq-gic-common.h"
>>  
>>  /*
>>  * MSI_TYPER:
>> @@ -83,7 +84,11 @@ static struct irq_chip gicv2m_msi_irq_chip = {
>>  	.irq_mask		= gicv2m_mask_msi_irq,
>>  	.irq_unmask		= gicv2m_unmask_msi_irq,
>>  	.irq_eoi		= irq_chip_eoi_parent,
>> -	.irq_write_msi_msg	= pci_msi_domain_write_msg,
>> +#ifdef CONFIG_IOMMU_API
>> +	.irq_write_msi_msg	= gic_pci_msi_domain_write_msg,
>> +#else
>> +	.irq_write_msi_msg      = pci_msi_domain_write_msg,
>> +#endif
> 
> Irrespective of the way you implement the translation procedure, you
> should make this unconditional, and have the #ifdefery in the code that
> implements it.

OK

Thanks

Eric
> 
>>  };
>>  
>>  static struct msi_domain_info gicv2m_msi_domain_info = {
>> diff --git a/drivers/irqchip/irq-gic-v3-its-pci-msi.c b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
>> index 8223765..690504e 100644
>> --- a/drivers/irqchip/irq-gic-v3-its-pci-msi.c
>> +++ b/drivers/irqchip/irq-gic-v3-its-pci-msi.c
>> @@ -19,6 +19,7 @@
>>  #include <linux/of.h>
>>  #include <linux/of_irq.h>
>>  #include <linux/of_pci.h>
>> +#include "irq-gic-common.h"
>>  
>>  static void its_mask_msi_irq(struct irq_data *d)
>>  {
>> @@ -37,7 +38,11 @@ static struct irq_chip its_msi_irq_chip = {
>>  	.irq_unmask		= its_unmask_msi_irq,
>>  	.irq_mask		= its_mask_msi_irq,
>>  	.irq_eoi		= irq_chip_eoi_parent,
>> +#ifdef CONFIG_IOMMU_API
>> +	.irq_write_msi_msg	= gic_pci_msi_domain_write_msg,
>> +#else
>>  	.irq_write_msi_msg	= pci_msi_domain_write_msg,
>> +#endif
>>  };
>>  
>>  struct its_pci_alias {
> 
> Thanks,
> 
> 	M.
>