RE: [PATCH v4 10/14] iommu: remove the share_p2m operation

["Tian, Kevin" <kevin.tian@intel.com>]

> From: Paul Durrant <paul@xen.org>
> Sent: Tuesday, August 4, 2020 9:42 PM
> 
> From: Paul Durrant <pdurrant@amazon.com>
> 
> Sharing of HAP tables is now VT-d specific so the operation is never defined
> for AMD IOMMU any more. There's also no need to pro-actively set
> vtd.pgd_maddr
> when using shared EPT as it is straightforward to simply define a helper
> function to return the appropriate value in the shared and non-shared cases.
> 
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>

Reviewed-by: Kevin Tian <kevin.tian@intel.com>

> ---
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> Cc: George Dunlap <george.dunlap@citrix.com>
> Cc: Wei Liu <wl@xen.org>
> Cc: "Roger Pau Monné" <roger.pau@citrix.com>
> Cc: Kevin Tian <kevin.tian@intel.com>
> 
> v2:
>   - Put the PGD level adjust into the helper function too, since it is
>     irrelevant in the shared EPT case
> ---
>  xen/arch/x86/mm/p2m.c               |  3 -
>  xen/drivers/passthrough/iommu.c     |  8 ---
>  xen/drivers/passthrough/vtd/iommu.c | 90 ++++++++++++++++-------------
>  xen/include/xen/iommu.h             |  3 -
>  4 files changed, 50 insertions(+), 54 deletions(-)
> 
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index 9f8b9bc5fd..3bd8d83d23 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -726,9 +726,6 @@ int p2m_alloc_table(struct p2m_domain *p2m)
> 
>      p2m->phys_table = pagetable_from_mfn(top_mfn);
> 
> -    if ( hap_enabled(d) )
> -        iommu_share_p2m_table(d);
> -
>      p2m_unlock(p2m);
>      return 0;
>  }
> diff --git a/xen/drivers/passthrough/iommu.c
> b/xen/drivers/passthrough/iommu.c
> index ab44c332bb..7464f10d1c 100644
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -498,14 +498,6 @@ int iommu_do_domctl(
>      return ret;
>  }
> 
> -void iommu_share_p2m_table(struct domain* d)
> -{
> -    ASSERT(hap_enabled(d));
> -
> -    if ( iommu_use_hap_pt(d) )
> -        iommu_get_ops()->share_p2m(d);
> -}
> -
>  void iommu_crash_shutdown(void)
>  {
>      if ( !iommu_crash_disable )
> diff --git a/xen/drivers/passthrough/vtd/iommu.c
> b/xen/drivers/passthrough/vtd/iommu.c
> index 68cf0e535a..a532d9e88c 100644
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -318,6 +318,48 @@ static u64 addr_to_dma_page_maddr(struct
> domain *domain, u64 addr, int alloc)
>      return pte_maddr;
>  }
> 
> +static uint64_t domain_pgd_maddr(struct domain *d, struct vtd_iommu
> *iommu)
> +{
> +    struct domain_iommu *hd = dom_iommu(d);
> +    uint64_t pgd_maddr;
> +    unsigned int agaw;
> +
> +    ASSERT(spin_is_locked(&hd->arch.mapping_lock));
> +
> +    if ( iommu_use_hap_pt(d) )
> +    {
> +        mfn_t pgd_mfn =
> +            pagetable_get_mfn(p2m_get_pagetable(p2m_get_hostp2m(d)));
> +
> +        return pagetable_get_paddr(pagetable_from_mfn(pgd_mfn));
> +    }
> +
> +    if ( !hd->arch.vtd.pgd_maddr )
> +    {
> +        addr_to_dma_page_maddr(d, 0, 1);
> +
> +        if ( !hd->arch.vtd.pgd_maddr )
> +            return 0;
> +    }
> +
> +    pgd_maddr = hd->arch.vtd.pgd_maddr;
> +
> +    /* Skip top levels of page tables for 2- and 3-level DRHDs. */
> +    for ( agaw = level_to_agaw(4);
> +          agaw != level_to_agaw(iommu->nr_pt_levels);
> +          agaw-- )
> +    {
> +        struct dma_pte *p = map_vtd_domain_page(pgd_maddr);
> +
> +        pgd_maddr = dma_pte_addr(*p);
> +        unmap_vtd_domain_page(p);
> +        if ( !pgd_maddr )
> +            return 0;
> +    }
> +
> +    return pgd_maddr;
> +}
> +
>  static void iommu_flush_write_buffer(struct vtd_iommu *iommu)
>  {
>      u32 val;
> @@ -1286,7 +1328,7 @@ int domain_context_mapping_one(
>      struct context_entry *context, *context_entries;
>      u64 maddr, pgd_maddr;
>      u16 seg = iommu->drhd->segment;
> -    int agaw, rc, ret;
> +    int rc, ret;
>      bool_t flush_dev_iotlb;
> 
>      ASSERT(pcidevs_locked());
> @@ -1340,37 +1382,18 @@ int domain_context_mapping_one(
>      if ( iommu_hwdom_passthrough && is_hardware_domain(domain) )
>      {
>          context_set_translation_type(*context, CONTEXT_TT_PASS_THRU);
> -        agaw = level_to_agaw(iommu->nr_pt_levels);
>      }
>      else
>      {
>          spin_lock(&hd->arch.mapping_lock);
> 
> -        /* Ensure we have pagetables allocated down to leaf PTE. */
> -        if ( hd->arch.vtd.pgd_maddr == 0 )
> +        pgd_maddr = domain_pgd_maddr(domain, iommu);
> +        if ( !pgd_maddr )
>          {
> -            addr_to_dma_page_maddr(domain, 0, 1);
> -            if ( hd->arch.vtd.pgd_maddr == 0 )
> -            {
> -            nomem:
> -                spin_unlock(&hd->arch.mapping_lock);
> -                spin_unlock(&iommu->lock);
> -                unmap_vtd_domain_page(context_entries);
> -                return -ENOMEM;
> -            }
> -        }
> -
> -        /* Skip top levels of page tables for 2- and 3-level DRHDs. */
> -        pgd_maddr = hd->arch.vtd.pgd_maddr;
> -        for ( agaw = level_to_agaw(4);
> -              agaw != level_to_agaw(iommu->nr_pt_levels);
> -              agaw-- )
> -        {
> -            struct dma_pte *p = map_vtd_domain_page(pgd_maddr);
> -            pgd_maddr = dma_pte_addr(*p);
> -            unmap_vtd_domain_page(p);
> -            if ( pgd_maddr == 0 )
> -                goto nomem;
> +            spin_unlock(&hd->arch.mapping_lock);
> +            spin_unlock(&iommu->lock);
> +            unmap_vtd_domain_page(context_entries);
> +            return -ENOMEM;
>          }
> 
>          context_set_address_root(*context, pgd_maddr);
> @@ -1389,7 +1412,7 @@ int domain_context_mapping_one(
>          return -EFAULT;
>      }
> 
> -    context_set_address_width(*context, agaw);
> +    context_set_address_width(*context, level_to_agaw(iommu-
> >nr_pt_levels));
>      context_set_fault_enable(*context);
>      context_set_present(*context);
>      iommu_sync_cache(context, sizeof(struct context_entry));
> @@ -1848,18 +1871,6 @@ static int __init vtd_ept_page_compatible(struct
> vtd_iommu *iommu)
>             (ept_has_1gb(ept_cap) && opt_hap_1gb) <= cap_sps_1gb(vtd_cap);
>  }
> 
> -/*
> - * set VT-d page table directory to EPT table if allowed
> - */
> -static void iommu_set_pgd(struct domain *d)
> -{
> -    mfn_t pgd_mfn;
> -
> -    pgd_mfn =
> pagetable_get_mfn(p2m_get_pagetable(p2m_get_hostp2m(d)));
> -    dom_iommu(d)->arch.vtd.pgd_maddr =
> -        pagetable_get_paddr(pagetable_from_mfn(pgd_mfn));
> -}
> -
>  static int rmrr_identity_mapping(struct domain *d, bool_t map,
>                                   const struct acpi_rmrr_unit *rmrr,
>                                   u32 flag)
> @@ -2719,7 +2730,6 @@ static struct iommu_ops __initdata vtd_ops = {
>      .adjust_irq_affinities = adjust_vtd_irq_affinities,
>      .suspend = vtd_suspend,
>      .resume = vtd_resume,
> -    .share_p2m = iommu_set_pgd,
>      .crash_shutdown = vtd_crash_shutdown,
>      .iotlb_flush = iommu_flush_iotlb_pages,
>      .iotlb_flush_all = iommu_flush_iotlb_all,
> diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
> index b7e5d3da09..1f25d2082f 100644
> --- a/xen/include/xen/iommu.h
> +++ b/xen/include/xen/iommu.h
> @@ -271,7 +271,6 @@ struct iommu_ops {
> 
>      int __must_check (*suspend)(void);
>      void (*resume)(void);
> -    void (*share_p2m)(struct domain *d);
>      void (*crash_shutdown)(void);
>      int __must_check (*iotlb_flush)(struct domain *d, dfn_t dfn,
>                                      unsigned long page_count,
> @@ -348,8 +347,6 @@ void iommu_resume(void);
>  void iommu_crash_shutdown(void);
>  int iommu_get_reserved_device_memory(iommu_grdm_t *, void *);
> 
> -void iommu_share_p2m_table(struct domain *d);
> -
>  #ifdef CONFIG_HAS_PCI
>  int iommu_do_pci_domctl(struct xen_domctl *, struct domain *d,
>                          XEN_GUEST_HANDLE_PARAM(xen_domctl_t));
> --
> 2.20.1