RE: [PATCH V2 4/6] hyperv/IOMMU: Enable swiotlb bounce buffer for Isolation VM

Michael Kelley (LINUX)
2021-11-23T17:45:18Z

From: Tianyu Lan <ltykernel@gmail.com> Sent: Tuesday, November 23, 2021 6:31 AM
>
> 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 call swiotlb_update_mem_attributes()
> in the hyperv_iommu_swiotlb_later_init().
>
> Add Hyper-V dma ops and provide alloc/free and vmap/vunmap noncontiguous
> callback to handle request of allocating and mapping noncontiguous dma
> memory in vmbus device driver. Netvsc driver will use this. Set dma_ops_
> bypass flag for hv device to use dma direct functions during mapping/unmapping
> dma page.
>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
> ---
> Change since v1:
> * Remove hv isolation check in the sev_setup_arch()
>
> arch/x86/mm/mem_encrypt.c | 1 +
> arch/x86/xen/pci-swiotlb-xen.c | 3 +-
> drivers/hv/Kconfig | 1 +
> drivers/hv/vmbus_drv.c | 6 ++
> drivers/iommu/hyperv-iommu.c | 164 +++++++++++++++++++++++++++++++++
> include/linux/hyperv.h | 10 ++
> 6 files changed, 184 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 35487305d8af..e48c73b3dd41 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -31,6 +31,7 @@
> #include <asm/processor-flags.h>
> #include <asm/msr.h>
> #include <asm/cmdline.h>
> +#include <asm/mshyperv.h>

There is no longer any need to add this #include since code changes to this
file in a previous version of the patch are now gone.

>
> #include "mm_internal.h"
>
> diff --git a/arch/x86/xen/pci-swiotlb-xen.c b/arch/x86/xen/pci-swiotlb-xen.c
> index 46df59aeaa06..30fd0600b008 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/Kconfig b/drivers/hv/Kconfig
> index dd12af20e467..d43b4cd88f57 100644
> --- a/drivers/hv/Kconfig
> +++ b/drivers/hv/Kconfig
> @@ -9,6 +9,7 @@ config HYPERV
> select PARAVIRT
> select X86_HV_CALLBACK_VECTOR if X86
> select VMAP_PFN
> + select DMA_OPS_BYPASS
> help
> Select this option to run Linux as a Hyper-V client operating
> system.
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 392c1ac4f819..32dc193e31cd 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -33,6 +33,7 @@
> #include <linux/random.h>
> #include <linux/kernel.h>
> #include <linux/syscore_ops.h>
> +#include <linux/dma-map-ops.h>
> #include <clocksource/hyperv_timer.h>
> #include "hyperv_vmbus.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 +2120,10 @@ int vmbus_device_register(struct hv_device *child_device_obj)
> }
> hv_debug_add_dev_dir(child_device_obj);
>
> + child_device_obj->device.dma_ops_bypass = true;
> + child_device_obj->device.dma_ops = &hyperv_iommu_dma_ops;
> + child_device_obj->device.dma_mask = &vmbus_dma_mask;
> + child_device_obj->device.dma_parms = &child_device_obj->dma_parms;
> return 0;
>
> err_kset_unregister:
> diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
> index e285a220c913..ebcb628e7e8f 100644
> --- a/drivers/iommu/hyperv-iommu.c
> +++ b/drivers/iommu/hyperv-iommu.c
> @@ -13,14 +13,21 @@
> #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 "irq_remapping.h"
>
> @@ -337,4 +344,161 @@ 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)
> +{
> + unsigned long hyperv_io_tlb_size;
> + void *hyperv_io_tlb_start;
> +
> + /*
> + * 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");
> +
> + swiotlb_init_with_tbl(hyperv_io_tlb_start,
> + hyperv_io_tlb_size >> IO_TLB_SHIFT, true);
> +}
> +
> +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.
> + */
> + if (hv_isolation_type_snp())
> + 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_update_mem_attributes() here.
> + */
> + swiotlb_update_mem_attributes();
> +}
> +
> +IOMMU_INIT_FINISH(hyperv_swiotlb_detect,
> + NULL, hyperv_iommu_swiotlb_init,
> + hyperv_iommu_swiotlb_later_init);
> +
> +static struct sg_table *hyperv_dma_alloc_noncontiguous(struct device *dev,
> + size_t size, enum dma_data_direction dir, gfp_t gfp,
> + unsigned long attrs)
> +{
> + struct dma_sgt_handle *sh;
> + struct page **pages;
> + int num_pages = size >> PAGE_SHIFT;

This assumes "size" is a multiple of PAGE_SIZE. Probably should round
up for safety.

> + void *vaddr, *ptr;
> + int rc, i;
> +
> + if (!hv_isolation_type_snp())
> + return NULL;
> +
> + sh = kmalloc(sizeof(*sh), gfp);
> + if (!sh)
> + return NULL;
> +
> + vaddr = vmalloc(size);
> + if (!vaddr)
> + goto free_sgt;
> +
> + pages = kvmalloc_array(num_pages, sizeof(struct page *),
> + GFP_KERNEL | __GFP_ZERO);
> + if (!pages)
> + goto free_mem;
> +
> + for (i = 0, ptr = vaddr; i < num_pages; ++i, ptr += PAGE_SIZE)
> + pages[i] = vmalloc_to_page(ptr);
> +
> + rc = sg_alloc_table_from_pages(&sh->sgt, pages, num_pages, 0, size, GFP_KERNEL);
> + if (rc)
> + goto free_pages;
> +
> + sh->sgt.sgl->dma_address = (dma_addr_t)vaddr;
> + sh->sgt.sgl->dma_length = size;

include/linux/scatterlist.h defines macros sg_dma_address() and
sg_dma_len() for accessing these two fields. It's probably best to use them.

> + sh->pages = pages;
> +
> + return &sh->sgt;
> +
> +free_pages:
> + kvfree(pages);
> +free_mem:
> + vfree(vaddr);
> +free_sgt:
> + kfree(sh);
> + return NULL;
> +}
> +
> +static void hyperv_dma_free_noncontiguous(struct device *dev, size_t size,
> + struct sg_table *sgt, enum dma_data_direction dir)
> +{
> + struct dma_sgt_handle *sh = sgt_handle(sgt);
> +
> + if (!hv_isolation_type_snp())
> + return;
> +
> + vfree((void *)sh->sgt.sgl->dma_address);

Use sg_dma_address()

> + sg_free_table(&sh->sgt);
> + kvfree(sh->pages);
> + kfree(sh);
> +}
> +
> +static void *hyperv_dma_vmap_noncontiguous(struct device *dev, size_t size,
> + struct sg_table *sgt)
> +{
> + int pg_count = size >> PAGE_SHIFT;

Round up so don't assume size is a multiple of PAGE_SIZE?

> + unsigned long *pfns;
> + struct page **pages = sgt_handle(sgt)->pages;
> + void *vaddr = NULL;
> + int i;
> +
> + if (!hv_isolation_type_snp())
> + return NULL;
> +
> + if (!pages)
> + return NULL;
> +
> + pfns = kcalloc(pg_count, sizeof(*pfns), GFP_KERNEL);
> + if (!pfns)
> + return NULL;
> +
> + for (i = 0; i < pg_count; i++)
> + pfns[i] = page_to_pfn(pages[i]) +
> + (ms_hyperv.shared_gpa_boundary >> PAGE_SHIFT);
> +
> + vaddr = vmap_pfn(pfns, pg_count, PAGE_KERNEL);
> + kfree(pfns);
> + return vaddr;
> +
> +}
> +
> +static void hyperv_dma_vunmap_noncontiguous(struct device *dev, void *addr)
> +{
> + if (!hv_isolation_type_snp())
> + return;
> + vunmap(addr);
> +}
> +
> +const struct dma_map_ops hyperv_iommu_dma_ops = {
> + .alloc_noncontiguous = hyperv_dma_alloc_noncontiguous,
> + .free_noncontiguous = hyperv_dma_free_noncontiguous,
> + .vmap_noncontiguous = hyperv_dma_vmap_noncontiguous,
> + .vunmap_noncontiguous = hyperv_dma_vunmap_noncontiguous,
> +};
> +EXPORT_SYMBOL_GPL(hyperv_iommu_dma_ops);
> +
> #endif
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index b823311eac79..4d44fb3b3f1c 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1726,6 +1726,16 @@ 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));
> +#ifdef CONFIG_HYPERV
> +int __init hyperv_swiotlb_detect(void);
> +#else
> +static inline int __init hyperv_swiotlb_detect(void)
> +{
> + return 0;
> +}
> +#endif
> +
> +extern const struct dma_map_ops hyperv_iommu_dma_ops;
>
> struct hyperv_pci_block_ops {
> int (*read_block)(struct pci_dev *dev, void *buf, unsigned int buf_len,
> --
> 2.25.1