Re: [Xen-devel] [PATCH v6 8/8] AMD/IOMMU: pre-fill all DTEs right after table allocation

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Jan 
> Beulich
> Sent: 19 September 2019 14:25
> To: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Suravee Suthikulpanit 
> <suravee.suthikulpanit@xxxxxxx>
> Subject: [Xen-devel] [PATCH v6 8/8] AMD/IOMMU: pre-fill all DTEs right after 
> table allocation
> 
> Make sure we don't leave any DTEs unexpected requests through which
> would be passed through untranslated. Set V and IV right away (with
> all other fields left as zero), relying on the V and/or IV bits
> getting cleared only by amd_iommu_set_root_page_table() and
> amd_iommu_set_intremap_table() under special pass-through circumstances.
> Switch back to initial settings in amd_iommu_disable_domain_device().
> 
> Take the liberty and also make the latter function static, constifying
> its first parameter at the same time, at this occasion.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

> ---
> v6: New.
> 
> ---
>  xen/drivers/passthrough/amd/iommu_init.c    |   22 +++++++++++++++++++---
>  xen/drivers/passthrough/amd/pci_amd_iommu.c |   20 ++++++++++++++++----
>  2 files changed, 35 insertions(+), 7 deletions(-)
> 
> --- a/xen/drivers/passthrough/amd/iommu_init.c
> +++ b/xen/drivers/passthrough/amd/iommu_init.c
> @@ -1255,12 +1255,28 @@ static int __init amd_iommu_setup_device
> 
>      if ( !dt )
>      {
> +        unsigned int size = dt_alloc_size();
> +
>          /* allocate 'device table' on a 4K boundary */
>          dt = IVRS_MAPPINGS_DEVTAB(ivrs_mappings) =
> -            allocate_buffer(dt_alloc_size(), "Device Table");
> +            allocate_buffer(size, "Device Table");
> +        if ( !dt )
> +            return -ENOMEM;
> +
> +        /*
> +         * Prefill every DTE such that all kinds of requests will get 
> aborted.
> +         * Besides the two bits set to true below this builds upon
> +         * IOMMU_DEV_TABLE_SYS_MGT_DMA_ABORTED,
> +         * IOMMU_DEV_TABLE_IO_CONTROL_ABORTED, as well as
> +         * IOMMU_DEV_TABLE_INT_CONTROL_ABORTED all being zero, and us also
> +         * wanting at least TV, GV, I, and EX set to false.
> +         */
> +        for ( bdf = 0, size /= sizeof(*dt); bdf < size; ++bdf )
> +        {
> +            dt[bdf].v = true;
> +            dt[bdf].iv = true;
> +        }
>      }
> -    if ( !dt )
> -        return -ENOMEM;
> 
>      /* Add device table entries */
>      for ( bdf = 0; bdf < ivrs_bdf_entries; bdf++ )
> --- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
> +++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
> @@ -267,9 +267,9 @@ static void __hwdom_init amd_iommu_hwdom
>      setup_hwdom_pci_devices(d, amd_iommu_add_device);
>  }
> 
> -void amd_iommu_disable_domain_device(struct domain *domain,
> -                                     struct amd_iommu *iommu,
> -                                     u8 devfn, struct pci_dev *pdev)
> +static void amd_iommu_disable_domain_device(const struct domain *domain,
> +                                            struct amd_iommu *iommu,
> +                                            uint8_t devfn, struct pci_dev 
> *pdev)
>  {
>      struct amd_iommu_dte *table, *dte;
>      unsigned long flags;
> @@ -284,9 +284,21 @@ void amd_iommu_disable_domain_device(str
>      spin_lock_irqsave(&iommu->lock, flags);
>      if ( dte->tv || dte->v )
>      {
> +        /* See the comment in amd_iommu_setup_device_table(). */
> +        dte->int_ctl = IOMMU_DEV_TABLE_INT_CONTROL_ABORTED;
> +        smp_wmb();
> +        dte->iv = true;
>          dte->tv = false;
> -        dte->v = false;
> +        dte->gv = false;
>          dte->i = false;
> +        dte->ex = false;
> +        dte->sa = false;
> +        dte->se = false;
> +        dte->sd = false;
> +        dte->sys_mgt = IOMMU_DEV_TABLE_SYS_MGT_DMA_ABORTED;
> +        dte->ioctl = IOMMU_DEV_TABLE_IO_CONTROL_ABORTED;
> +        smp_wmb();
> +        dte->v = true;
> 
>          amd_iommu_flush_device(iommu, req_id);
> 
> 
> 
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