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

[Duan, Zhenzhong]

Hi Eric,

>-----Original Message-----
>From: Eric Auger <eric.auger@redhat.com>
>Subject: Re: [PATCH rfcv1 6/6] intel_iommu: add a framework to check and
>sync host IOMMU cap/ecap
>
>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.

I think your patch works with iommufd BE too😊 Because iommufd BE
also fills bcontainer->iova_ranges in iommufd_cdev_get_info_iova_range().

> In my case I want to pass the reserved memory regions which
>also model the aw.
>So this is a pretty similar use case.

Yes.

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

Passing iommu_hw_info is ok for this series, but we want more from
IOMMUFDDevice in nesting series. I.e., allocate/free ioas/hwpt,
attach/detach from hwpt, get dirty bitmap, etc. It's more flexible to
let vIOMMU get what it want itself.

>
>
>
>> +        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?

I'll doc it. Above we have one line to explain when cap/ecap are initialized.
vtd_init() is called in qemu init and guest reset. In qemu init,
Cap/ecap is finalized, after that we don't want cap/ecap to be changed.
So we bypass change to cap/ecap here.

>>
>>      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).

Will bump vtd_vmstate .version_id works?

Thanks
Zhenzhong

>
>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(),