[PATCH V5 10/12] hyperv/IOMMU: Enable swiotlb bounce buffer for Isolation VM

Tianyu Lan
2021-09-14T13:40:34Z

From: Tianyu Lan <Tianyu.Lan@microsoft.com>

hyperv Isolation VM requires bounce buffer support to copy
data from/to encrypted memory and so enable swiotlb force
mode to use swiotlb bounce buffer for DMA transaction.

In Isolation VM with AMD SEV, the bounce buffer needs to be
accessed via extra address space which is above shared_gpa_boundary
(E.G 39 bit address line) reported by Hyper-V CPUID ISOLATION_CONFIG.
The access physical address will be original physical address +
shared_gpa_boundary. The shared_gpa_boundary in the AMD SEV SNP
spec is called virtual top of memory(vTOM). Memory addresses below
vTOM are automatically treated as private while memory above
vTOM is treated as shared.

Hyper-V initalizes swiotlb bounce buffer and default swiotlb
needs to be disabled. pci_swiotlb_detect_override() and
pci_swiotlb_detect_4gb() enable the default one. To override
the setting, hyperv_swiotlb_detect() needs to run before
these detect functions which depends on the pci_xen_swiotlb_
init(). Make pci_xen_swiotlb_init() depends on the hyperv_swiotlb
_detect() to keep the order.

Swiotlb bounce buffer code calls set_memory_decrypted()
to mark bounce buffer visible to host and map it in extra
address space via memremap. Populate the shared_gpa_boundary
(vTOM) via swiotlb_unencrypted_base variable.

The map function memremap() can't work in the early place
hyperv_iommu_swiotlb_init() and so initialize swiotlb bounce
buffer in the hyperv_iommu_swiotlb_later_init().

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
---
Change since v4:
* Use swiotlb_unencrypted_base variable to pass shared_gpa_
boundary and map bounce buffer inside swiotlb code.

Change since v3:
* Get hyperv bounce bufffer size via default swiotlb
bounce buffer size function and keep default size as
same as the one in the AMD SEV VM.
---
arch/x86/include/asm/mshyperv.h | 2 ++
arch/x86/mm/mem_encrypt.c | 3 +-
arch/x86/xen/pci-swiotlb-xen.c | 3 +-
drivers/hv/vmbus_drv.c | 3 ++
drivers/iommu/hyperv-iommu.c | 60 +++++++++++++++++++++++++++++++++
include/linux/hyperv.h | 1 +
6 files changed, 70 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 165423e8b67a..2d22f29f90c9 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -182,6 +182,8 @@ int hv_map_ioapic_interrupt(int ioapic_id, bool level, int vcpu, int vector,
struct hv_interrupt_entry *entry);
int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry);
int hv_set_mem_host_visibility(unsigned long addr, int numpages, bool visible);
+void *hv_map_memory(void *addr, unsigned long size);
+void hv_unmap_memory(void *addr);
void hv_ghcb_msr_write(u64 msr, u64 value);
void hv_ghcb_msr_read(u64 msr, u64 *value);
#else /* CONFIG_HYPERV */
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index ff08dc463634..e2db0b8ed938 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -30,6 +30,7 @@
#include <asm/processor-flags.h>
#include <asm/msr.h>
#include <asm/cmdline.h>
+#include <asm/mshyperv.h>

#include "mm_internal.h"

@@ -202,7 +203,7 @@ void __init sev_setup_arch(void)
phys_addr_t total_mem = memblock_phys_mem_size();
unsigned long size;

- if (!sev_active())
+ if (!sev_active() && !hv_is_isolation_supported())
return;

/*
diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
index 54f9aa7e8457..43bd031aa332 100644
--- a/arch/x86/xen/pci-swiotlb-xen.c
+++ b/arch/x86/xen/pci-swiotlb-xen.c
@@ -4,6 +4,7 @@

#include <linux/dma-map-ops.h>
#include <linux/pci.h>
+#include <linux/hyperv.h>
#include <xen/swiotlb-xen.h>

#include <asm/xen/hypervisor.h>
@@ -91,6 +92,6 @@ int pci_xen_swiotlb_init_late(void)
EXPORT_SYMBOL_GPL(pci_xen_swiotlb_init_late);

IOMMU_INIT_FINISH(pci_xen_swiotlb_detect,
- NULL,
+ hyperv_swiotlb_detect,
pci_xen_swiotlb_init,
NULL);
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 392c1ac4f819..b0be287e9a32 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -23,6 +23,7 @@
#include <linux/cpu.h>
#include <linux/sched/task_stack.h>

+#include <linux/dma-map-ops.h>
#include <linux/delay.h>
#include <linux/notifier.h>
#include <linux/panic_notifier.h>
@@ -2078,6 +2079,7 @@ struct hv_device *vmbus_device_create(const guid_t *type,
return child_device_obj;
}

+static u64 vmbus_dma_mask = DMA_BIT_MASK(64);
/*
* vmbus_device_register - Register the child device
*/
@@ -2118,6 +2120,7 @@ int vmbus_device_register(struct hv_device *child_device_obj)
}
hv_debug_add_dev_dir(child_device_obj);

+ child_device_obj->device.dma_mask = &vmbus_dma_mask;
return 0;

err_kset_unregister:
diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
index e285a220c913..a8ac2239de0f 100644
--- a/drivers/iommu/hyperv-iommu.c
+++ b/drivers/iommu/hyperv-iommu.c
@@ -13,14 +13,22 @@
#include <linux/irq.h>
#include <linux/iommu.h>
#include <linux/module.h>
+#include <linux/hyperv.h>
+#include <linux/io.h>

#include <asm/apic.h>
#include <asm/cpu.h>
#include <asm/hw_irq.h>
#include <asm/io_apic.h>
+#include <asm/iommu.h>
+#include <asm/iommu_table.h>
#include <asm/irq_remapping.h>
#include <asm/hypervisor.h>
#include <asm/mshyperv.h>
+#include <asm/swiotlb.h>
+#include <linux/dma-map-ops.h>
+#include <linux/dma-direct.h>
+#include <linux/set_memory.h>

#include "irq_remapping.h"

@@ -36,6 +44,9 @@
static cpumask_t ioapic_max_cpumask = { CPU_BITS_NONE };
static struct irq_domain *ioapic_ir_domain;

+static unsigned long hyperv_io_tlb_size;
+static void *hyperv_io_tlb_start;
+
static int hyperv_ir_set_affinity(struct irq_data *data,
const struct cpumask *mask, bool force)
{
@@ -337,4 +348,53 @@ static const struct irq_domain_ops hyperv_root_ir_domain_ops = {
.free = hyperv_root_irq_remapping_free,
};

+static void __init hyperv_iommu_swiotlb_init(void)
+{
+ /*
+ * Allocate Hyper-V swiotlb bounce buffer at early place
+ * to reserve large contiguous memory.
+ */
+ hyperv_io_tlb_size = swiotlb_size_or_default();
+ hyperv_io_tlb_start = memblock_alloc(
+ hyperv_io_tlb_size, PAGE_SIZE);
+
+ if (!hyperv_io_tlb_start) {
+ pr_warn("Fail to allocate Hyper-V swiotlb buffer.\n");
+ return;
+ }
+}
+
+int __init hyperv_swiotlb_detect(void)
+{
+ if (!hypervisor_is_type(X86_HYPER_MS_HYPERV))
+ return 0;
+
+ if (!hv_is_isolation_supported())
+ return 0;
+
+ /*
+ * Enable swiotlb force mode in Isolation VM to
+ * use swiotlb bounce buffer for dma transaction.
+ */
+ swiotlb_unencrypted_base = ms_hyperv.shared_gpa_boundary;
+ swiotlb_force = SWIOTLB_FORCE;
+ return 1;
+}
+
+static void __init hyperv_iommu_swiotlb_later_init(void)
+{
+ /*
+ * Swiotlb bounce buffer needs to be mapped in extra address
+ * space. Map function doesn't work in the early place and so
+ * call swiotlb_late_init_with_tbl() here.
+ */
+ if (swiotlb_late_init_with_tbl(hyperv_io_tlb_start,
+ hyperv_io_tlb_size >> IO_TLB_SHIFT))
+ panic("Fail to initialize hyperv swiotlb.\n");
+}
+
+IOMMU_INIT_FINISH(hyperv_swiotlb_detect,
+ NULL, hyperv_iommu_swiotlb_init,
+ hyperv_iommu_swiotlb_later_init);
+
#endif
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index a9e0bc3b1511..bb1a1519b93a 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1739,6 +1739,7 @@ int hyperv_write_cfg_blk(struct pci_dev *dev, void *buf, unsigned int len,
int hyperv_reg_block_invalidate(struct pci_dev *dev, void *context,
void (*block_invalidate)(void *context,
u64 block_mask));
+int __init hyperv_swiotlb_detect(void);

struct hyperv_pci_block_ops {
int (*read_block)(struct pci_dev *dev, void *buf, unsigned int buf_len,
--
2.25.1