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

[Michael Kelley <mikelley@xxxxxxxxxxxxx>]

From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Tuesday, September 14, 2021 6:39 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 initialize swiotlb bounce
> buffer in the hyperv_iommu_swiotlb_later_init().
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
> 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);

Aren't these two declarations now spurious?

>  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