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

["Michael Kelley (LINUX)" <mikelley@xxxxxxxxxxxxx>]

From: Tianyu Lan <ltykernel@xxxxxxxxx> 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@xxxxxxxxxxxxx>
> ---
> 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