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Intel IOMMU Pass Through Support 

The patch adds kernel parameter intel_iommu=pt to set up pass through
mode in context mapping entry. This disables DMAR in linux kernel; but
KVM still runs on VT-d and interrupt remapping still works.

In this mode, kernel uses swiotlb for DMA API functions but other VT-d
functionalities are enabled for KVM. KVM always uses multi level
translation page table in VT-d. By default, pass though mode is disabled
in kernel.

This is useful when people don't want to enable VT-d DMAR in kernel but
still want to use KVM and interrupt remapping for reasons like DMAR
performance concern or debug purpose.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Acked-by: Weidong Han <weidong@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
This commit is contained in:
Fenghua Yu 2009-04-24 17:30:20 -07:00 committed by David Woodhouse
parent 0910697403
commit 4ed0d3e6c6
10 changed files with 166 additions and 51 deletions
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1
Documentation/kernel-parameters.txt
View File

@ -965,6 +965,7 @@ and is between 256 and 4096 characters. It is defined in the file
nomerge
forcesac
soft
pt [x86, IA64]
io7= [HW] IO7 for Marvel based alpha systems
See comment before marvel_specify_io7 in

1
arch/ia64/include/asm/iommu.h
View File

@ -9,6 +9,7 @@ extern void pci_iommu_shutdown(void);
extern void no_iommu_init(void);
extern int force_iommu, no_iommu;
extern int iommu_detected;
extern int iommu_pass_through;
extern void iommu_dma_init(void);
extern void machvec_init(const char *name);

2
arch/ia64/kernel/pci-swiotlb.c
View File

@ -46,7 +46,7 @@ void __init swiotlb_dma_init(void)
void __init pci_swiotlb_init(void)
{
if (!iommu_detected) {
if (!iommu_detected || iommu_pass_through) {
#ifdef CONFIG_IA64_GENERIC
swiotlb = 1;
printk(KERN_INFO "PCI-DMA: Re-initialize machine vector.\n");

1
arch/x86/include/asm/iommu.h
View File

@ -6,6 +6,7 @@ extern void no_iommu_init(void);
extern struct dma_map_ops nommu_dma_ops;
extern int force_iommu, no_iommu;
extern int iommu_detected;
extern int iommu_pass_through;
/* 10 seconds */
#define DMAR_OPERATION_TIMEOUT ((cycles_t) tsc_khz*10*1000)

6
arch/x86/kernel/pci-dma.c
View File

@ -160,6 +160,8 @@ again:
return page_address(page);
}
extern int iommu_pass_through;
/*
* See <Documentation/x86_64/boot-options.txt> for the iommu kernel parameter
* documentation.
@ -209,6 +211,10 @@ static __init int iommu_setup(char *p)
#ifdef CONFIG_SWIOTLB
if (!strncmp(p, "soft", 4))
swiotlb = 1;
if (!strncmp(p, "pt", 2)) {
iommu_pass_through = 1;
return 1;
}
#endif
gart_parse_options(p);

3
arch/x86/kernel/pci-swiotlb.c
View File

@ -71,7 +71,8 @@ void __init pci_swiotlb_init(void)
{
/* don't initialize swiotlb if iommu=off (no_iommu=1) */
#ifdef CONFIG_X86_64
if (!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN)
if ((!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN) ||
iommu_pass_through)
swiotlb = 1;
#endif
if (swiotlb_force)

11
drivers/pci/dmar.c
View File

@ -515,6 +515,7 @@ int alloc_iommu(struct dmar_drhd_unit *drhd)
u32 ver;
static int iommu_allocated = 0;
int agaw = 0;
int msagaw = 0;
iommu = kzalloc(sizeof(*iommu), GFP_KERNEL);
if (!iommu)
@ -535,12 +536,20 @@ int alloc_iommu(struct dmar_drhd_unit *drhd)
agaw = iommu_calculate_agaw(iommu);
if (agaw < 0) {
printk(KERN_ERR
"Cannot get a valid agaw for iommu (seq_id = %d)\n",
"Cannot get a valid agaw for iommu (seq_id = %d)\n",
iommu->seq_id);
goto error;
}
msagaw = iommu_calculate_max_sagaw(iommu);
if (msagaw < 0) {
printk(KERN_ERR
"Cannot get a valid max agaw for iommu (seq_id = %d)\n",
iommu->seq_id);
goto error;
}
#endif
iommu->agaw = agaw;
iommu->msagaw = msagaw;
/* the registers might be more than one page */
map_size = max_t(int, ecap_max_iotlb_offset(iommu->ecap),

182
drivers/pci/intel-iommu.c
View File

@ -53,6 +53,8 @@
#define DEFAULT_DOMAIN_ADDRESS_WIDTH 48
#define MAX_AGAW_WIDTH 64
#define DOMAIN_MAX_ADDR(gaw) ((((u64)1) << gaw) - 1)
#define IOVA_PFN(addr) ((addr) >> PAGE_SHIFT)
@ -127,8 +129,6 @@ static inline void context_set_fault_enable(struct context_entry *context)
context->lo &= (((u64)-1) << 2) | 1;
}
#define CONTEXT_TT_MULTI_LEVEL 0
static inline void context_set_translation_type(struct context_entry *context,
unsigned long value)
{
@ -288,6 +288,7 @@ int dmar_disabled = 1;
static int __initdata dmar_map_gfx = 1;
static int dmar_forcedac;
static int intel_iommu_strict;
int iommu_pass_through;
#define DUMMY_DEVICE_DOMAIN_INFO ((struct device_domain_info *)(-1))
static DEFINE_SPINLOCK(device_domain_lock);
@ -397,17 +398,13 @@ void free_iova_mem(struct iova *iova)
static inline int width_to_agaw(int width);
/* calculate agaw for each iommu.
* "SAGAW" may be different across iommus, use a default agaw, and
* get a supported less agaw for iommus that don't support the default agaw.
*/
int iommu_calculate_agaw(struct intel_iommu *iommu)
static int __iommu_calculate_agaw(struct intel_iommu *iommu, int max_gaw)
{
unsigned long sagaw;
int agaw = -1;
sagaw = cap_sagaw(iommu->cap);
for (agaw = width_to_agaw(DEFAULT_DOMAIN_ADDRESS_WIDTH);
for (agaw = width_to_agaw(max_gaw);
agaw >= 0; agaw--) {
if (test_bit(agaw, &sagaw))
break;
@ -416,6 +413,24 @@ int iommu_calculate_agaw(struct intel_iommu *iommu)
return agaw;
}
/*
* Calculate max SAGAW for each iommu.
*/
int iommu_calculate_max_sagaw(struct intel_iommu *iommu)
{
return __iommu_calculate_agaw(iommu, MAX_AGAW_WIDTH);
}
/*
* calculate agaw for each iommu.
* "SAGAW" may be different across iommus, use a default agaw, and
* get a supported less agaw for iommus that don't support the default agaw.
*/
int iommu_calculate_agaw(struct intel_iommu *iommu)
{
return __iommu_calculate_agaw(iommu, DEFAULT_DOMAIN_ADDRESS_WIDTH);
}
/* in native case, each domain is related to only one iommu */
static struct intel_iommu *domain_get_iommu(struct dmar_domain *domain)
{
@ -1321,8 +1336,8 @@ static void domain_exit(struct dmar_domain *domain)
free_domain_mem(domain);
}
static int domain_context_mapping_one(struct dmar_domain *domain,
int segment, u8 bus, u8 devfn)
static int domain_context_mapping_one(struct dmar_domain *domain, int segment,
u8 bus, u8 devfn, int translation)
{
struct context_entry *context;
unsigned long flags;
@ -1335,7 +1350,10 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
pr_debug("Set context mapping for %02x:%02x.%d\n",
bus, PCI_SLOT(devfn), PCI_FUNC(devfn));
BUG_ON(!domain->pgd);
BUG_ON(translation != CONTEXT_TT_PASS_THROUGH &&
translation != CONTEXT_TT_MULTI_LEVEL);
iommu = device_to_iommu(segment, bus, devfn);
if (!iommu)
@ -1395,9 +1413,18 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
}
context_set_domain_id(context, id);
context_set_address_width(context, iommu->agaw);
context_set_address_root(context, virt_to_phys(pgd));
context_set_translation_type(context, CONTEXT_TT_MULTI_LEVEL);
/*
* In pass through mode, AW must be programmed to indicate the largest
* AGAW value supported by hardware. And ASR is ignored by hardware.
*/
if (likely(translation == CONTEXT_TT_MULTI_LEVEL)) {
context_set_address_width(context, iommu->agaw);
context_set_address_root(context, virt_to_phys(pgd));
} else
context_set_address_width(context, iommu->msagaw);
context_set_translation_type(context, translation);
context_set_fault_enable(context);
context_set_present(context);
domain_flush_cache(domain, context, sizeof(*context));
@ -1422,13 +1449,15 @@ static int domain_context_mapping_one(struct dmar_domain *domain,
}
static int
domain_context_mapping(struct dmar_domain *domain, struct pci_dev *pdev)
domain_context_mapping(struct dmar_domain *domain, struct pci_dev *pdev,
int translation)
{
int ret;
struct pci_dev *tmp, *parent;
ret = domain_context_mapping_one(domain, pci_domain_nr(pdev->bus),
pdev->bus->number, pdev->devfn);
pdev->bus->number, pdev->devfn,
translation);
if (ret)
return ret;
@ -1442,7 +1471,7 @@ domain_context_mapping(struct dmar_domain *domain, struct pci_dev *pdev)
ret = domain_context_mapping_one(domain,
pci_domain_nr(parent->bus),
parent->bus->number,
parent->devfn);
parent->devfn, translation);
if (ret)
return ret;
parent = parent->bus->self;
@ -1450,12 +1479,14 @@ domain_context_mapping(struct dmar_domain *domain, struct pci_dev *pdev)
if (tmp->is_pcie) /* this is a PCIE-to-PCI bridge */
return domain_context_mapping_one(domain,
pci_domain_nr(tmp->subordinate),
tmp->subordinate->number, 0);
tmp->subordinate->number, 0,
translation);
else /* this is a legacy PCI bridge */
return domain_context_mapping_one(domain,
pci_domain_nr(tmp->bus),
tmp->bus->number,
tmp->devfn);
tmp->devfn,
translation);
}
static int domain_context_mapped(struct pci_dev *pdev)
@ -1752,7 +1783,7 @@ static int iommu_prepare_identity_map(struct pci_dev *pdev,
goto error;
/* context entry init */
ret = domain_context_mapping(domain, pdev);
ret = domain_context_mapping(domain, pdev, CONTEXT_TT_MULTI_LEVEL);
if (!ret)
return 0;
error:
@ -1853,6 +1884,23 @@ static inline void iommu_prepare_isa(void)
}
#endif /* !CONFIG_DMAR_FLPY_WA */
/* Initialize each context entry as pass through.*/
static int __init init_context_pass_through(void)
{
struct pci_dev *pdev = NULL;
struct dmar_domain *domain;
int ret;
for_each_pci_dev(pdev) {
domain = get_domain_for_dev(pdev, DEFAULT_DOMAIN_ADDRESS_WIDTH);
ret = domain_context_mapping(domain, pdev,
CONTEXT_TT_PASS_THROUGH);
if (ret)
return ret;
}
return 0;
}
static int __init init_dmars(void)
{
struct dmar_drhd_unit *drhd;
@ -1860,6 +1908,7 @@ static int __init init_dmars(void)
struct pci_dev *pdev;
struct intel_iommu *iommu;
int i, ret;
int pass_through = 1;
/*
* for each drhd
@ -1913,7 +1962,15 @@ static int __init init_dmars(void)
printk(KERN_ERR "IOMMU: allocate root entry failed\n");
goto error;
}
if (!ecap_pass_through(iommu->ecap))
pass_through = 0;
}
if (iommu_pass_through)
if (!pass_through) {
printk(KERN_INFO
"Pass Through is not supported by hardware.\n");
iommu_pass_through = 0;
}
/*
* Start from the sane iommu hardware state.
@ -1976,37 +2033,57 @@ static int __init init_dmars(void)
"IOMMU: enable interrupt remapping failed\n");
}
#endif
/*
* For each rmrr
* for each dev attached to rmrr
* do
* locate drhd for dev, alloc domain for dev
* allocate free domain
* allocate page table entries for rmrr
* if context not allocated for bus
* allocate and init context
* set present in root table for this bus
* init context with domain, translation etc
* endfor
* endfor
* If pass through is set and enabled, context entries of all pci
* devices are intialized by pass through translation type.
*/
for_each_rmrr_units(rmrr) {
for (i = 0; i < rmrr->devices_cnt; i++) {
pdev = rmrr->devices[i];
/* some BIOS lists non-exist devices in DMAR table */
if (!pdev)
continue;
ret = iommu_prepare_rmrr_dev(rmrr, pdev);
if (ret)
printk(KERN_ERR
"IOMMU: mapping reserved region failed\n");
if (iommu_pass_through) {
ret = init_context_pass_through();
if (ret) {
printk(KERN_ERR "IOMMU: Pass through init failed.\n");
iommu_pass_through = 0;
}
}
iommu_prepare_gfx_mapping();
/*
* If pass through is not set or not enabled, setup context entries for
* identity mappings for rmrr, gfx, and isa.
*/
if (!iommu_pass_through) {
/*
* For each rmrr
* for each dev attached to rmrr
* do
* locate drhd for dev, alloc domain for dev
* allocate free domain
* allocate page table entries for rmrr
* if context not allocated for bus
* allocate and init context
* set present in root table for this bus
* init context with domain, translation etc
* endfor
* endfor
*/
for_each_rmrr_units(rmrr) {
for (i = 0; i < rmrr->devices_cnt; i++) {
pdev = rmrr->devices[i];
/*
* some BIOS lists non-exist devices in DMAR
* table.
*/
if (!pdev)
continue;
ret = iommu_prepare_rmrr_dev(rmrr, pdev);
if (ret)
printk(KERN_ERR
"IOMMU: mapping reserved region failed\n");
}
}
iommu_prepare_isa();
iommu_prepare_gfx_mapping();
iommu_prepare_isa();
}
/*
* for each drhd
@ -2117,7 +2194,8 @@ get_valid_domain_for_dev(struct pci_dev *pdev)
/* make sure context mapping is ok */
if (unlikely(!domain_context_mapped(pdev))) {
ret = domain_context_mapping(domain, pdev);
ret = domain_context_mapping(domain, pdev,
CONTEXT_TT_MULTI_LEVEL);
if (ret) {
printk(KERN_ERR
"Domain context map for %s failed",
@ -2786,7 +2864,7 @@ int __init intel_iommu_init(void)
* Check the need for DMA-remapping initialization now.
* Above initialization will also be used by Interrupt-remapping.
*/
if (no_iommu || swiotlb || dmar_disabled)
if (no_iommu || (swiotlb && !iommu_pass_through) || dmar_disabled)
return -ENODEV;
iommu_init_mempool();
@ -2806,7 +2884,15 @@ int __init intel_iommu_init(void)
init_timer(&unmap_timer);
force_iommu = 1;
dma_ops = &intel_dma_ops;
if (!iommu_pass_through) {
printk(KERN_INFO
"Multi-level page-table translation for DMAR.\n");
dma_ops = &intel_dma_ops;
} else
printk(KERN_INFO
"DMAR: Pass through translation for DMAR.\n");
init_iommu_sysfs();
register_iommu(&intel_iommu_ops);
@ -3146,7 +3232,7 @@ static int intel_iommu_attach_device(struct iommu_domain *domain,
return -EFAULT;
}
ret = domain_context_mapping(dmar_domain, pdev);
ret = domain_context_mapping(dmar_domain, pdev, CONTEXT_TT_MULTI_LEVEL);
if (ret)
return ret;

8
include/linux/dma_remapping.h
View File

@ -13,6 +13,9 @@
#define DMA_PTE_WRITE (2)
#define DMA_PTE_SNP (1 << 11)
#define CONTEXT_TT_MULTI_LEVEL 0
#define CONTEXT_TT_PASS_THROUGH 2
struct intel_iommu;
struct dmar_domain;
struct root_entry;
@ -21,11 +24,16 @@ extern void free_dmar_iommu(struct intel_iommu *iommu);
#ifdef CONFIG_DMAR
extern int iommu_calculate_agaw(struct intel_iommu *iommu);
extern int iommu_calculate_max_sagaw(struct intel_iommu *iommu);
#else
static inline int iommu_calculate_agaw(struct intel_iommu *iommu)
{
return 0;
}
static inline int iommu_calculate_max_sagaw(struct intel_iommu *iommu)
{
return 0;
}
#endif
extern int dmar_disabled;

2
include/linux/intel-iommu.h
View File

@ -120,6 +120,7 @@ static inline void dmar_writeq(void __iomem *addr, u64 val)
(ecap_iotlb_offset(e) + ecap_niotlb_iunits(e) * 16)
#define ecap_coherent(e) ((e) & 0x1)
#define ecap_qis(e) ((e) & 0x2)
#define ecap_pass_through(e) ((e >> 6) & 0x1)
#define ecap_eim_support(e) ((e >> 4) & 0x1)
#define ecap_ir_support(e) ((e >> 3) & 0x1)
#define ecap_max_handle_mask(e) ((e >> 20) & 0xf)
@ -302,6 +303,7 @@ struct intel_iommu {
spinlock_t register_lock; /* protect register handling */
int seq_id; /* sequence id of the iommu */
int agaw; /* agaw of this iommu */
int msagaw; /* max sagaw of this iommu */
unsigned int irq;
unsigned char name[13]; /* Device Name */