lkml.org 
[lkml]   [2019]   [Apr]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH 2/7] iommu/dma-iommu: Split iommu_dma_map_msi_msg in two parts
From
Date
Hi Marc,

On 23/04/2019 11:54, Marc Zyngier wrote:
> On 18/04/2019 18:26, Julien Grall wrote:
>> On RT, the function iommu_dma_map_msi_msg may be called from
>> non-preemptible context. This will lead to a splat with
>> CONFIG_DEBUG_ATOMIC_SLEEP as the function is using spin_lock
>> (they can sleep on RT).
>>
>> The function iommu_dma_map_msi_msg is used to map the MSI page in the
>> IOMMU PT and update the MSI message with the IOVA.
>>
>> Only the part to lookup for the MSI page requires to be called in
>> preemptible context. As the MSI page cannot change over the lifecycle
>> of the MSI interrupt, the lookup can be cached and re-used later on.
>>
>> This patch split the function iommu_dma_map_msi_msg in two new
>> functions:
>> - iommu_dma_prepare_msi: This function will prepare the mapping in
>> the IOMMU and store the cookie in the structure msi_desc. This
>> function should be called in preemptible context.
>> - iommu_dma_compose_msi_msg: This function will update the MSI
>> message with the IOVA when the device is behind an IOMMU.
>>
>> Signed-off-by: Julien Grall <julien.grall@arm.com>
>> ---
>> drivers/iommu/dma-iommu.c | 43 ++++++++++++++++++++++++++++++++-----------
>> include/linux/dma-iommu.h | 21 +++++++++++++++++++++
>> 2 files changed, 53 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index 77aabe637a60..f5c1f1685095 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -888,17 +888,17 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
>> return NULL;
>> }
>>
>> -void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg)
>> +int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr)
>
> I quite like the idea of moving from having an irq to having an msi_desc
> passed to the IOMMU layer...
>
>> {
>> - struct device *dev = msi_desc_to_dev(irq_get_msi_desc(irq));
>> + struct device *dev = msi_desc_to_dev(desc);
>> struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
>> struct iommu_dma_cookie *cookie;
>> - struct iommu_dma_msi_page *msi_page;
>> - phys_addr_t msi_addr = (u64)msg->address_hi << 32 | msg->address_lo;
>> unsigned long flags;
>>
>> - if (!domain || !domain->iova_cookie)
>> - return;
>> + if (!domain || !domain->iova_cookie) {
>> + desc->iommu_cookie = NULL;
>> + return 0;
>> + }
>>
>> cookie = domain->iova_cookie;
>>
>> @@ -908,10 +908,33 @@ void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg)
>> * of an MSI from within an IPI handler.
>> */
>> spin_lock_irqsave(&cookie->msi_lock, flags);
>> - msi_page = iommu_dma_get_msi_page(dev, msi_addr, domain);
>> + desc->iommu_cookie = iommu_dma_get_msi_page(dev, msi_addr, domain);
>> spin_unlock_irqrestore(&cookie->msi_lock, flags);
>>
>> - if (WARN_ON(!msi_page)) {
>> + return (desc->iommu_cookie) ? 0 : -ENOMEM;
>> +}
>> +
>> +void iommu_dma_compose_msi_msg(int irq, struct msi_msg *msg)
>
> ... but I'd like it even better if it was uniform. Can you please move
> the irq_get_msi_desc() to the callers of iommu_dma_compose_msi_msg(),
> and make both functions take a msi_desc?

Make sense. I will modify iommu_dma_compose_msi_msg to take a msi_desc in parameter.

Cheers,

--
Julien Grall

\
 
 \ /
  Last update: 2019-04-29 15:14    [W:0.053 / U:0.844 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site