Re: [PATCH rfcv1 6/6] intel_iommu: add a framework to check and sync host IOMMU cap/ecap

[Eric Auger <eric.auger@redhat.com>]

Hi Zhenzhong,

On 1/15/24 11:13, Zhenzhong Duan wrote:
> From: Yi Liu <yi.l.liu@intel.com>
>
> Add a framework to check and synchronize host IOMMU cap/ecap with
> vIOMMU cap/ecap.
>
> Currently only stage-2 translation is supported which is backed by
> shadow page table on host side. So we don't need exact matching of
> each bit of cap/ecap between vIOMMU and host. However, we can still
> utilize this framework to ensure compatibility of host and vIOMMU's
> address width at least, i.e., vIOMMU's aw_bits <= host aw_bits,
> which is missed before.
>
> When stage-1 translation is supported in future, a.k.a. scalable
> modern mode, we need to ensure compatibility of each bits. Some
> bits are user controllable, they should be checked with host side
> to ensure compatibility. Other bits are not, they should be synced
> into vIOMMU cap/ecap for compatibility.
>
> The sequence will be:
>
> vtd_cap_init() initializes iommu->cap/ecap. ---- vtd_cap_init()
> iommu->host_cap/ecap is initialized as iommu->cap/ecap.  ---- vtd_init()
> iommu->host_cap/ecap is checked and updated some bits with host cap/ecap. ---- vtd_sync_hw_info()
> iommu->cap/ecap is finalized as iommu->host_cap/ecap.  ---- vtd_machine_done_hook()
>
> iommu->host_cap/ecap is a temporary storage to hold intermediate value
> when synthesize host cap/ecap and vIOMMU's initial configured cap/ecap.
>
> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>  include/hw/i386/intel_iommu.h |  4 ++
>  hw/i386/intel_iommu.c         | 78 +++++++++++++++++++++++++++++++----
>  2 files changed, 75 insertions(+), 7 deletions(-)
>
> diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
> index c65fdde56f..b8abbcce12 100644
> --- a/include/hw/i386/intel_iommu.h
> +++ b/include/hw/i386/intel_iommu.h
> @@ -292,6 +292,9 @@ struct IntelIOMMUState {
>      uint64_t cap;                   /* The value of capability reg */
>      uint64_t ecap;                  /* The value of extended capability reg */
>  
> +    uint64_t host_cap;              /* The value of host capability reg */
> +    uint64_t host_ecap;             /* The value of host ext-capability reg */
> +
>      uint32_t context_cache_gen;     /* Should be in [1,MAX] */
>      GHashTable *iotlb;              /* IOTLB */
>  
> @@ -314,6 +317,7 @@ struct IntelIOMMUState {
>      bool dma_translation;           /* Whether DMA translation supported */
>      bool pasid;                     /* Whether to support PASID */
>  
> +    bool cap_finalized;             /* Whether VTD capability finalized */
>      /*
>       * Protects IOMMU states in general.  Currently it protects the
>       * per-IOMMU IOTLB cache, and context entry cache in VTDAddressSpace.
> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> index 4c1d058ebd..be03fcbf52 100644
> --- a/hw/i386/intel_iommu.c
> +++ b/hw/i386/intel_iommu.c
> @@ -3819,6 +3819,47 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus,
>      return vtd_dev_as;
>  }
>  
> +static bool vtd_sync_hw_info(IntelIOMMUState *s, struct iommu_hw_info_vtd *vtd,
> +                             Error **errp)
> +{
> +    uint64_t addr_width;
> +
> +    addr_width = (vtd->cap_reg >> 16) & 0x3fULL;
> +    if (s->aw_bits > addr_width) {
> +        error_setg(errp, "User aw-bits: %u > host address width: %lu",
> +                   s->aw_bits, addr_width);
> +        return false;
> +    }
> +
> +    /* TODO: check and sync host cap/ecap into vIOMMU cap/ecap */
> +
> +    return true;
> +}
> +
> +/*
> + * virtual VT-d which wants nested needs to check the host IOMMU
> + * nesting cap info behind the assigned devices. Thus that vIOMMU
> + * could bind guest page table to host.
> + */
> +static bool vtd_check_idev(IntelIOMMUState *s, IOMMUFDDevice *idev,
> +                           Error **errp)
> +{
> +    struct iommu_hw_info_vtd vtd;
> +    enum iommu_hw_info_type type = IOMMU_HW_INFO_TYPE_INTEL_VTD;
> +
> +    if (iommufd_device_get_info(idev, &type, sizeof(vtd), &vtd)) {
> +        error_setg(errp, "Failed to get IOMMU capability!!!");
> +        return false;
> +    }
> +
> +    if (type != IOMMU_HW_INFO_TYPE_INTEL_VTD) {
> +        error_setg(errp, "IOMMU hardware is not compatible!!!");
> +        return false;
> +    }
> +
> +    return vtd_sync_hw_info(s, &vtd, errp);
> +}
> +
>  static int vtd_dev_set_iommu_device(PCIBus *bus, void *opaque, int32_t devfn,
>                                      IOMMUFDDevice *idev, Error **errp)
>  {
> @@ -3837,6 +3878,10 @@ static int vtd_dev_set_iommu_device(PCIBus *bus, void *opaque, int32_t devfn,
>          return 0;
>      }
>  
> +    if (!vtd_check_idev(s, idev, errp)) {In
In
[RFC 0/7] VIRTIO-IOMMU/VFIO: Fix host iommu geometry handling for
hotplugged devices
https://lore.kernel.org/all/20240117080414.316890-1-eric.auger@redhat.com/

I also attempt to pass host iommu info to the virtio-iommu but with
legacy BE. In my case I want to pass the reserved memory regions which
also model the aw.
So this is a pretty similar use case.

Why don't we pass the pointer to an opaque iommu_hw_info instead,
through the PCIIOMMUOps?



> +        return -1;
> +    }
> +
>      vtd_iommu_lock(s);
>  
>      vtd_idev = g_hash_table_lookup(s->vtd_iommufd_dev, &key);
> @@ -4071,10 +4116,11 @@ static void vtd_init(IntelIOMMUState *s)
>  {
>      X86IOMMUState *x86_iommu = X86_IOMMU_DEVICE(s);
>  
> -    memset(s->csr, 0, DMAR_REG_SIZE);
> -    memset(s->wmask, 0, DMAR_REG_SIZE);
> -    memset(s->w1cmask, 0, DMAR_REG_SIZE);
> -    memset(s->womask, 0, DMAR_REG_SIZE);
> +    /* CAP/ECAP are initialized in machine create done stage */
> +    memset(s->csr + DMAR_GCMD_REG, 0, DMAR_REG_SIZE - DMAR_GCMD_REG);
> +    memset(s->wmask + DMAR_GCMD_REG, 0, DMAR_REG_SIZE - DMAR_GCMD_REG);
> +    memset(s->w1cmask + DMAR_GCMD_REG, 0, DMAR_REG_SIZE - DMAR_GCMD_REG);
> +    memset(s->womask + DMAR_GCMD_REG, 0, DMAR_REG_SIZE - DMAR_GCMD_REG);
This change is not documented in the commit msg.
Sorry I don't get why this is needed?
>  
>      s->root = 0;
>      s->root_scalable = false;
> @@ -4110,13 +4156,16 @@ static void vtd_init(IntelIOMMUState *s)
>          vtd_spte_rsvd_large[3] &= ~VTD_SPTE_SNP;
>      }
>  
> -    vtd_cap_init(s);
> +    if (!s->cap_finalized) {
> +        vtd_cap_init(s);
> +        s->host_cap = s->cap;
> +        s->host_ecap = s->ecap;
> +    }
> +
>      vtd_reset_caches(s);
>  
>      /* Define registers with default values and bit semantics */
>      vtd_define_long(s, DMAR_VER_REG, 0x10UL, 0, 0);
> -    vtd_define_quad(s, DMAR_CAP_REG, s->cap, 0, 0);
> -    vtd_define_quad(s, DMAR_ECAP_REG, s->ecap, 0, 0);
>      vtd_define_long(s, DMAR_GCMD_REG, 0, 0xff800000UL, 0);
>      vtd_define_long_wo(s, DMAR_GCMD_REG, 0xff800000UL);
>      vtd_define_long(s, DMAR_GSTS_REG, 0, 0, 0);
> @@ -4241,6 +4290,12 @@ static bool vtd_decide_config(IntelIOMMUState *s, Error **errp)
>      return true;
>  }
>  
> +static void vtd_setup_capability_reg(IntelIOMMUState *s)
> +{
> +    vtd_define_quad(s, DMAR_CAP_REG, s->cap, 0, 0);
> +    vtd_define_quad(s, DMAR_ECAP_REG, s->ecap, 0, 0);
> +}
> +
>  static int vtd_machine_done_notify_one(Object *child, void *unused)
>  {
>      IntelIOMMUState *iommu = INTEL_IOMMU_DEVICE(x86_iommu_get_default());
> @@ -4259,6 +4314,14 @@ static int vtd_machine_done_notify_one(Object *child, void *unused)
>  
>  static void vtd_machine_done_hook(Notifier *notifier, void *unused)
>  {
> +    IntelIOMMUState *iommu = INTEL_IOMMU_DEVICE(x86_iommu_get_default());
> +
> +    iommu->cap = iommu->host_cap;
> +    iommu->ecap = iommu->host_ecap;
> +    iommu->cap_finalized = true;
I don't think you can change the defaults like this without taking care
of compats (migration).

Thanks

Eric
> +
> +    vtd_setup_capability_reg(iommu);
> +
>      object_child_foreach_recursive(object_get_root(),
>                                     vtd_machine_done_notify_one, NULL);
>  }
> @@ -4292,6 +4355,7 @@ static void vtd_realize(DeviceState *dev, Error **errp)
>  
>      QLIST_INIT(&s->vtd_as_with_notifiers);
>      qemu_mutex_init(&s->iommu_lock);
> +    s->cap_finalized = false;
>      memory_region_init_io(&s->csrmem, OBJECT(s), &vtd_mem_ops, s,
>                            "intel_iommu", DMAR_REG_SIZE);
>      memory_region_add_subregion(get_system_memory(),