RE: [PATCH v9 7/8] iommu: remove the share_p2m operation

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

> From: Tian, Kevin
> Sent: Thursday, September 17, 2020 3:20 PM
> 
> > From: Paul Durrant <paul@xxxxxxx>
> > Sent: Tuesday, September 15, 2020 4:30 PM
> >
> > From: Paul Durrant <pdurrant@xxxxxxxxxx>
> >
> > 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.
> 
> vtd_dump_p2m_table then also needs to use this helper if I didn't overlook.
> 

Please forget this comment. If hap sharing, that callback won't be
invoked. So:

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

> 
> >
> > NOTE: This patch also modifies unmap_vtd_domain_page() to take a const
> >       pointer since the only thing it calls, unmap_domain_page(), also takes
> >       a const pointer.
> >
> > Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> > ---
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
> > Cc: Wei Liu <wl@xxxxxxx>
> > Cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
> > Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
> >
> > v6:
> >  - Adjust code to return P2M paddr
> >  - Add removed comment back in
> >
> > v5:
> >  - Pass 'nr_pt_levels' into domain_pgd_maddr() directly
> >
> > 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/extern.h  |  2 +-
> >  xen/drivers/passthrough/vtd/iommu.c   | 90 +++++++++++++++------------
> >  xen/drivers/passthrough/vtd/x86/vtd.c |  2 +-
> >  xen/include/xen/iommu.h               |  3 -
> >  6 files changed, 52 insertions(+), 56 deletions(-)
> >
> > diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> > index 01ff92862d..d382199c88 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 a9da4d2b06..90748062e5 100644
> > --- a/xen/drivers/passthrough/iommu.c
> > +++ b/xen/drivers/passthrough/iommu.c
> > @@ -500,14 +500,6 @@ 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/extern.h
> > b/xen/drivers/passthrough/vtd/extern.h
> > index ada3c3098c..9cf5b578c9 100644
> > --- a/xen/drivers/passthrough/vtd/extern.h
> > +++ b/xen/drivers/passthrough/vtd/extern.h
> > @@ -72,7 +72,7 @@ void flush_all_cache(void);
> >  uint64_t alloc_pgtable_maddr(unsigned long npages, nodeid_t node);
> >  void free_pgtable_maddr(u64 maddr);
> >  void *map_vtd_domain_page(u64 maddr);
> > -void unmap_vtd_domain_page(void *va);
> > +void unmap_vtd_domain_page(const void *va);
> >  int domain_context_mapping_one(struct domain *domain, struct
> > vtd_iommu *iommu,
> >                                 u8 bus, u8 devfn, const struct pci_dev *);
> >  int domain_context_unmap_one(struct domain *domain, struct
> vtd_iommu
> > *iommu,
> > diff --git a/xen/drivers/passthrough/vtd/iommu.c
> > b/xen/drivers/passthrough/vtd/iommu.c
> > index 68cf0e535a..58d4550a4c 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, unsigned int
> > nr_pt_levels)
> > +{
> > +    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) )
> > +    {
> > +        pagetable_t pgt = p2m_get_pagetable(p2m_get_hostp2m(d));
> > +
> > +        return pagetable_get_paddr(pgt);
> > +    }
> > +
> > +    if ( !hd->arch.vtd.pgd_maddr )
> > +    {
> > +        /* Ensure we have pagetables allocated down to leaf PTE. */
> > +        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(nr_pt_levels);
> > +          agaw-- )
> > +    {
> > +        const 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 )
> > -        {
> > -            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-- )
> > +        pgd_maddr = domain_pgd_maddr(domain, iommu->nr_pt_levels);
> > +        if ( !pgd_maddr )
> >          {
> > -            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/drivers/passthrough/vtd/x86/vtd.c
> > b/xen/drivers/passthrough/vtd/x86/vtd.c
> > index bbe358dc36..6681dccd69 100644
> > --- a/xen/drivers/passthrough/vtd/x86/vtd.c
> > +++ b/xen/drivers/passthrough/vtd/x86/vtd.c
> > @@ -42,7 +42,7 @@ void *map_vtd_domain_page(u64 maddr)
> >      return map_domain_page(_mfn(paddr_to_pfn(maddr)));
> >  }
> >
> > -void unmap_vtd_domain_page(void *va)
> > +void unmap_vtd_domain_page(const void *va)
> >  {
> >      unmap_domain_page(va);
> >  }
> > diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
> > index a2eefe8582..373145266f 100644
> > --- a/xen/include/xen/iommu.h
> > +++ b/xen/include/xen/iommu.h
> > @@ -270,7 +270,6 @@ 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,
> > @@ -347,8 +346,6 @@ 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