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rmurphy-armwildea01
rmurphy-arm
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wildea01
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iommu/dma: Allow MSI-only cookies
IOMMU domain users such as VFIO face a similar problem to DMA API ops with regard to mapping MSI messages in systems where the MSI write is subject to IOMMU translation. With the relevant infrastructure now in place for managed DMA domains, it's actually really simple for other users to piggyback off that and reap the benefits without giving up their own IOVA management, and without having to reinvent their own wheel in the MSI layer. Allow such users to opt into automatic MSI remapping by dedicating a region of their IOVA space to a managed cookie, and extend the mapping routine to implement a trivial linear allocator in such cases, to avoid the needless overhead of a full-blown IOVA domain. Signed-off-by: Robin Murphy <robin.murphy@arm.com> Reviewed-by: Tomasz Nowicki <tomasz.nowicki@caviumnetworks.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Tested-by: Eric Auger <eric.auger@redhat.com> Tested-by: Tomasz Nowicki <tomasz.nowicki@caviumnetworks.com> Tested-by: Bharat Bhushan <bharat.bhushan@nxp.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
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2 files changed

+102
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‎drivers/iommu/dma-iommu.c

Lines changed: 96 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -37,15 +37,50 @@ struct iommu_dma_msi_page {
3737
phys_addr_t phys;
3838
};
3939

40+
enum iommu_dma_cookie_type {
41+
IOMMU_DMA_IOVA_COOKIE,
42+
IOMMU_DMA_MSI_COOKIE,
43+
};
44+
4045
struct iommu_dma_cookie {
41-
struct iova_domain iovad;
42-
struct list_head msi_page_list;
43-
spinlock_t msi_lock;
46+
enum iommu_dma_cookie_type type;
47+
union {
48+
/* Full allocator for IOMMU_DMA_IOVA_COOKIE */
49+
struct iova_domain iovad;
50+
/* Trivial linear page allocator for IOMMU_DMA_MSI_COOKIE */
51+
dma_addr_t msi_iova;
52+
};
53+
struct list_head msi_page_list;
54+
spinlock_t msi_lock;
4455
};
4556

57+
static inline size_t cookie_msi_granule(struct iommu_dma_cookie *cookie)
58+
{
59+
if (cookie->type == IOMMU_DMA_IOVA_COOKIE)
60+
return cookie->iovad.granule;
61+
return PAGE_SIZE;
62+
}
63+
4664
static inline struct iova_domain *cookie_iovad(struct iommu_domain *domain)
4765
{
48-
return &((struct iommu_dma_cookie *)domain->iova_cookie)->iovad;
66+
struct iommu_dma_cookie *cookie = domain->iova_cookie;
67+
68+
if (cookie->type == IOMMU_DMA_IOVA_COOKIE)
69+
return &cookie->iovad;
70+
return NULL;
71+
}
72+
73+
static struct iommu_dma_cookie *cookie_alloc(enum iommu_dma_cookie_type type)
74+
{
75+
struct iommu_dma_cookie *cookie;
76+
77+
cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
78+
if (cookie) {
79+
spin_lock_init(&cookie->msi_lock);
80+
INIT_LIST_HEAD(&cookie->msi_page_list);
81+
cookie->type = type;
82+
}
83+
return cookie;
4984
}
5085

5186
int iommu_dma_init(void)
@@ -61,26 +96,54 @@ int iommu_dma_init(void)
6196
* callback when domain->type == IOMMU_DOMAIN_DMA.
6297
*/
6398
int iommu_get_dma_cookie(struct iommu_domain *domain)
99+
{
100+
if (domain->iova_cookie)
101+
return -EEXIST;
102+
103+
domain->iova_cookie = cookie_alloc(IOMMU_DMA_IOVA_COOKIE);
104+
if (!domain->iova_cookie)
105+
return -ENOMEM;
106+
107+
return 0;
108+
}
109+
EXPORT_SYMBOL(iommu_get_dma_cookie);
110+
111+
/**
112+
* iommu_get_msi_cookie - Acquire just MSI remapping resources
113+
* @domain: IOMMU domain to prepare
114+
* @base: Start address of IOVA region for MSI mappings
115+
*
116+
* Users who manage their own IOVA allocation and do not want DMA API support,
117+
* but would still like to take advantage of automatic MSI remapping, can use
118+
* this to initialise their own domain appropriately. Users should reserve a
119+
* contiguous IOVA region, starting at @base, large enough to accommodate the
120+
* number of PAGE_SIZE mappings necessary to cover every MSI doorbell address
121+
* used by the devices attached to @domain.
122+
*/
123+
int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
64124
{
65125
struct iommu_dma_cookie *cookie;
66126

127+
if (domain->type != IOMMU_DOMAIN_UNMANAGED)
128+
return -EINVAL;
129+
67130
if (domain->iova_cookie)
68131
return -EEXIST;
69132

70-
cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
133+
cookie = cookie_alloc(IOMMU_DMA_MSI_COOKIE);
71134
if (!cookie)
72135
return -ENOMEM;
73136

74-
spin_lock_init(&cookie->msi_lock);
75-
INIT_LIST_HEAD(&cookie->msi_page_list);
137+
cookie->msi_iova = base;
76138
domain->iova_cookie = cookie;
77139
return 0;
78140
}
79-
EXPORT_SYMBOL(iommu_get_dma_cookie);
141+
EXPORT_SYMBOL(iommu_get_msi_cookie);
80142

81143
/**
82144
* iommu_put_dma_cookie - Release a domain's DMA mapping resources
83-
* @domain: IOMMU domain previously prepared by iommu_get_dma_cookie()
145+
* @domain: IOMMU domain previously prepared by iommu_get_dma_cookie() or
146+
* iommu_get_msi_cookie()
84147
*
85148
* IOMMU drivers should normally call this from their domain_free callback.
86149
*/
@@ -92,7 +155,7 @@ void iommu_put_dma_cookie(struct iommu_domain *domain)
92155
if (!cookie)
93156
return;
94157

95-
if (cookie->iovad.granule)
158+
if (cookie->type == IOMMU_DMA_IOVA_COOKIE && cookie->iovad.granule)
96159
put_iova_domain(&cookie->iovad);
97160

98161
list_for_each_entry_safe(msi, tmp, &cookie->msi_page_list, list) {
@@ -137,11 +200,12 @@ static void iova_reserve_pci_windows(struct pci_dev *dev,
137200
int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
138201
u64 size, struct device *dev)
139202
{
140-
struct iova_domain *iovad = cookie_iovad(domain);
203+
struct iommu_dma_cookie *cookie = domain->iova_cookie;
204+
struct iova_domain *iovad = &cookie->iovad;
141205
unsigned long order, base_pfn, end_pfn;
142206

143-
if (!iovad)
144-
return -ENODEV;
207+
if (!cookie || cookie->type != IOMMU_DMA_IOVA_COOKIE)
208+
return -EINVAL;
145209

146210
/* Use the smallest supported page size for IOVA granularity */
147211
order = __ffs(domain->pgsize_bitmap);
@@ -662,11 +726,12 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
662726
{
663727
struct iommu_dma_cookie *cookie = domain->iova_cookie;
664728
struct iommu_dma_msi_page *msi_page;
665-
struct iova_domain *iovad = &cookie->iovad;
729+
struct iova_domain *iovad = cookie_iovad(domain);
666730
struct iova *iova;
667731
int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
732+
size_t size = cookie_msi_granule(cookie);
668733

669-
msi_addr &= ~(phys_addr_t)iova_mask(iovad);
734+
msi_addr &= ~(phys_addr_t)(size - 1);
670735
list_for_each_entry(msi_page, &cookie->msi_page_list, list)
671736
if (msi_page->phys == msi_addr)
672737
return msi_page;
@@ -675,21 +740,29 @@ static struct iommu_dma_msi_page *iommu_dma_get_msi_page(struct device *dev,
675740
if (!msi_page)
676741
return NULL;
677742

678-
iova = __alloc_iova(domain, iovad->granule, dma_get_mask(dev));
679-
if (!iova)
680-
goto out_free_page;
681-
682743
msi_page->phys = msi_addr;
683-
msi_page->iova = iova_dma_addr(iovad, iova);
684-
if (iommu_map(domain, msi_page->iova, msi_addr, iovad->granule, prot))
744+
if (iovad) {
745+
iova = __alloc_iova(domain, size, dma_get_mask(dev));
746+
if (!iova)
747+
goto out_free_page;
748+
msi_page->iova = iova_dma_addr(iovad, iova);
749+
} else {
750+
msi_page->iova = cookie->msi_iova;
751+
cookie->msi_iova += size;
752+
}
753+
754+
if (iommu_map(domain, msi_page->iova, msi_addr, size, prot))
685755
goto out_free_iova;
686756

687757
INIT_LIST_HEAD(&msi_page->list);
688758
list_add(&msi_page->list, &cookie->msi_page_list);
689759
return msi_page;
690760

691761
out_free_iova:
692-
__free_iova(iovad, iova);
762+
if (iovad)
763+
__free_iova(iovad, iova);
764+
else
765+
cookie->msi_iova -= size;
693766
out_free_page:
694767
kfree(msi_page);
695768
return NULL;
@@ -730,7 +803,7 @@ void iommu_dma_map_msi_msg(int irq, struct msi_msg *msg)
730803
msg->data = ~0U;
731804
} else {
732805
msg->address_hi = upper_32_bits(msi_page->iova);
733-
msg->address_lo &= iova_mask(&cookie->iovad);
806+
msg->address_lo &= cookie_msi_granule(cookie) - 1;
734807
msg->address_lo += lower_32_bits(msi_page->iova);
735808
}
736809
}

‎include/linux/dma-iommu.h

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -27,6 +27,7 @@ int iommu_dma_init(void);
2727

2828
/* Domain management interface for IOMMU drivers */
2929
int iommu_get_dma_cookie(struct iommu_domain *domain);
30+
int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base);
3031
void iommu_put_dma_cookie(struct iommu_domain *domain);
3132

3233
/* Setup call for arch DMA mapping code */
@@ -86,6 +87,11 @@ static inline int iommu_get_dma_cookie(struct iommu_domain *domain)
8687
return -ENODEV;
8788
}
8889

90+
static inline int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
91+
{
92+
return -ENODEV;
93+
}
94+
8995
static inline void iommu_put_dma_cookie(struct iommu_domain *domain)
9096
{
9197
}

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