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>
diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 001b328..1312182 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
}
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(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 @@
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 @@
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 @@
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 @@
}
#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 @@
struct pci_dev *pdev;
struct intel_iommu *iommu;
int i, ret;
+ int pass_through = 1;
/*
* for each drhd
@@ -1913,7 +1962,15 @@
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 @@
"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 @@
/* 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 @@
* 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 @@
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 @@
return -EFAULT;
}
- ret = domain_context_mapping(dmar_domain, pdev);
+ ret = domain_context_mapping(dmar_domain, pdev, CONTEXT_TT_MULTI_LEVEL);
if (ret)
return ret;