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iommu: Make iommu_dma_prepare_msi() into a generic operation
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SW_MSI supports IOMMU to translate an MSI message before the MSI message
is delivered to the interrupt controller. On such systems, an iommu_domain
must have a translation for the MSI message for interrupts to work.

The IRQ subsystem will call into IOMMU to request that a physical page be
set up to receive MSI messages, and the IOMMU then sets an IOVA that maps
to that physical page. Ultimately the IOVA is programmed into the device
via the msi_msg.

Generalize this by allowing iommu_domain owners to provide implementations
of this mapping. Add a function pointer in struct iommu_domain to allow a
domain owner to provide its own implementation.

Have dma-iommu supply its implementation for IOMMU_DOMAIN_DMA types during
the iommu_get_dma_cookie() path. For IOMMU_DOMAIN_UNMANAGED types used by
VFIO (and iommufd for now), have the same iommu_dma_sw_msi set as well in
the iommu_get_msi_cookie() path.

Hold the group mutex while in iommu_dma_prepare_msi() to ensure the domain
doesn't change or become freed while running. Races with IRQ operations
from VFIO and domain changes from iommufd are possible here.

Replace the msi_prepare_lock with a lockdep assertion for the group mutex
as documentation. For the dmau_iommu.c each iommu_domain is unique to a
group.

Link: https://patch.msgid.link/r/4ca696150d2baee03af27c4ddefdb7b0b0280e7b.1740014950.git.nicolinc@nvidia.com
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
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Jason Gunthorpe committed Feb 21, 2025
1 parent 9349887 commit 288683c
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Showing 3 changed files with 73 additions and 33 deletions.
33 changes: 14 additions & 19 deletions drivers/iommu/dma-iommu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@
#include <linux/memremap.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/msi.h>
#include <linux/of_iommu.h>
#include <linux/pci.h>
#include <linux/scatterlist.h>
Expand Down Expand Up @@ -102,6 +103,9 @@ static int __init iommu_dma_forcedac_setup(char *str)
}
early_param("iommu.forcedac", iommu_dma_forcedac_setup);

static int iommu_dma_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
phys_addr_t msi_addr);

/* Number of entries per flush queue */
#define IOVA_DEFAULT_FQ_SIZE 256
#define IOVA_SINGLE_FQ_SIZE 32768
Expand Down Expand Up @@ -398,6 +402,7 @@ int iommu_get_dma_cookie(struct iommu_domain *domain)
return -ENOMEM;

mutex_init(&domain->iova_cookie->mutex);
iommu_domain_set_sw_msi(domain, iommu_dma_sw_msi);
return 0;
}

Expand Down Expand Up @@ -429,6 +434,7 @@ int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)

cookie->msi_iova = base;
domain->iova_cookie = cookie;
iommu_domain_set_sw_msi(domain, iommu_dma_sw_msi);
return 0;
}
EXPORT_SYMBOL(iommu_get_msi_cookie);
Expand All @@ -443,6 +449,9 @@ void iommu_put_dma_cookie(struct iommu_domain *domain)
struct iommu_dma_cookie *cookie = domain->iova_cookie;
struct iommu_dma_msi_page *msi, *tmp;

if (domain->sw_msi != iommu_dma_sw_msi)
return;

if (!cookie)
return;

Expand Down Expand Up @@ -1800,33 +1809,19 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
return NULL;
}

/**
* iommu_dma_prepare_msi() - Map the MSI page in the IOMMU domain
* @desc: MSI descriptor, will store the MSI page
* @msi_addr: MSI target address to be mapped
*
* Return: 0 on success or negative error code if the mapping failed.
*/
int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr)
static int iommu_dma_sw_msi(struct iommu_domain *domain, struct msi_desc *desc,
phys_addr_t msi_addr)
{
struct device *dev = msi_desc_to_dev(desc);
struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
struct iommu_dma_msi_page *msi_page;
static DEFINE_MUTEX(msi_prepare_lock); /* see below */
const struct iommu_dma_msi_page *msi_page;

if (!domain || !domain->iova_cookie) {
if (!domain->iova_cookie) {
msi_desc_set_iommu_msi_iova(desc, 0, 0);
return 0;
}

/*
* In fact the whole prepare operation should already be serialised by
* irq_domain_mutex further up the callchain, but that's pretty subtle
* on its own, so consider this locking as failsafe documentation...
*/
mutex_lock(&msi_prepare_lock);
iommu_group_mutex_assert(dev);
msi_page = iommu_dma_get_msi_page(dev, msi_addr, domain);
mutex_unlock(&msi_prepare_lock);
if (!msi_page)
return -ENOMEM;

Expand Down
29 changes: 29 additions & 0 deletions drivers/iommu/iommu.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3596,3 +3596,32 @@ int iommu_replace_group_handle(struct iommu_group *group,
return ret;
}
EXPORT_SYMBOL_NS_GPL(iommu_replace_group_handle, "IOMMUFD_INTERNAL");

#if IS_ENABLED(CONFIG_IRQ_MSI_IOMMU)
/**
* iommu_dma_prepare_msi() - Map the MSI page in the IOMMU domain
* @desc: MSI descriptor, will store the MSI page
* @msi_addr: MSI target address to be mapped
*
* The implementation of sw_msi() should take msi_addr and map it to
* an IOVA in the domain and call msi_desc_set_iommu_msi_iova() with the
* mapping information.
*
* Return: 0 on success or negative error code if the mapping failed.
*/
int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr)
{
struct device *dev = msi_desc_to_dev(desc);
struct iommu_group *group = dev->iommu_group;
int ret = 0;

if (!group)
return 0;

mutex_lock(&group->mutex);
if (group->domain && group->domain->sw_msi)
ret = group->domain->sw_msi(group->domain, desc, msi_addr);
mutex_unlock(&group->mutex);
return ret;
}
#endif /* CONFIG_IRQ_MSI_IOMMU */
44 changes: 30 additions & 14 deletions include/linux/iommu.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,8 @@ struct iommu_dma_cookie;
struct iommu_fault_param;
struct iommufd_ctx;
struct iommufd_viommu;
struct msi_desc;
struct msi_msg;

#define IOMMU_FAULT_PERM_READ (1 << 0) /* read */
#define IOMMU_FAULT_PERM_WRITE (1 << 1) /* write */
Expand Down Expand Up @@ -216,6 +218,12 @@ struct iommu_domain {
struct iommu_domain_geometry geometry;
struct iommu_dma_cookie *iova_cookie;
int (*iopf_handler)(struct iopf_group *group);

#if IS_ENABLED(CONFIG_IRQ_MSI_IOMMU)
int (*sw_msi)(struct iommu_domain *domain, struct msi_desc *desc,
phys_addr_t msi_addr);
#endif

void *fault_data;
union {
struct {
Expand All @@ -234,6 +242,16 @@ struct iommu_domain {
};
};

static inline void iommu_domain_set_sw_msi(
struct iommu_domain *domain,
int (*sw_msi)(struct iommu_domain *domain, struct msi_desc *desc,
phys_addr_t msi_addr))
{
#if IS_ENABLED(CONFIG_IRQ_MSI_IOMMU)
domain->sw_msi = sw_msi;
#endif
}

static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
{
return domain->type & __IOMMU_DOMAIN_DMA_API;
Expand Down Expand Up @@ -1470,6 +1488,18 @@ static inline ioasid_t iommu_alloc_global_pasid(struct device *dev)
static inline void iommu_free_global_pasid(ioasid_t pasid) {}
#endif /* CONFIG_IOMMU_API */

#ifdef CONFIG_IRQ_MSI_IOMMU
#ifdef CONFIG_IOMMU_API
int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr);
#else
static inline int iommu_dma_prepare_msi(struct msi_desc *desc,
phys_addr_t msi_addr)
{
return 0;
}
#endif /* CONFIG_IOMMU_API */
#endif /* CONFIG_IRQ_MSI_IOMMU */

#if IS_ENABLED(CONFIG_LOCKDEP) && IS_ENABLED(CONFIG_IOMMU_API)
void iommu_group_mutex_assert(struct device *dev);
#else
Expand Down Expand Up @@ -1503,26 +1533,12 @@ static inline void iommu_debugfs_setup(void) {}
#endif

#ifdef CONFIG_IOMMU_DMA
#include <linux/msi.h>

int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base);

int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr);

#else /* CONFIG_IOMMU_DMA */

struct msi_desc;
struct msi_msg;

static inline int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
{
return -ENODEV;
}

static inline int iommu_dma_prepare_msi(struct msi_desc *desc, phys_addr_t msi_addr)
{
return 0;
}
#endif /* CONFIG_IOMMU_DMA */

/*
Expand Down

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