Re: [PATCH v5 04/17] vt-d: VT-d Posted-Interrupts feature detection

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Aug 12, 2015 at 10:35:25AM +0800, Feng Wu wrote:
> VT-d Posted-Interrupts is an enhancement to CPU side Posted-Interrupt.
> With VT-d Posted-Interrupts enabled, external interrupts from
> direct-assigned devices can be delivered to guests without VMM
> intervention when guest is running in non-root mode.
> 
> CC: Yang Zhang <yang.z.zhang@intel.com>
> CC: Kevin Tian <kevin.tian@intel.com>
> Signed-off-by: Feng Wu <feng.wu@intel.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
> v5:
> - Remove blank line
> 
> v4:
> - Correct a logic error when setting iommu_intpost to 0
> 
> v3:
> - Remove the "if no intremap then no intpost" logic in
>   intel_vtd_setup(), it is covered in the iommu_setup().
> - Add "if no intremap then no intpost" logic in the end
>   of init_vtd_hw() which is called by vtd_resume().
> 
> So the logic exists in the following three places:
> - parse_iommu_param()
> - iommu_setup()
> - init_vtd_hw()
> 
>  xen/drivers/passthrough/vtd/iommu.c | 17 +++++++++++++++--
>  xen/drivers/passthrough/vtd/iommu.h |  1 +
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
> index 1dffc40..52c7cc9 100644
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -2079,6 +2079,9 @@ static int init_vtd_hw(void)
>                  disable_intremap(drhd->iommu);
>      }
>  
> +    if ( !iommu_intremap )
> +        iommu_intpost = 0;
> +
>      /*
>       * Set root entries for each VT-d engine.  After set root entry,
>       * must globally invalidate context cache, and then globally
> @@ -2147,8 +2150,8 @@ int __init intel_vtd_setup(void)
>      }
>  
>      /* We enable the following features only if they are supported by all VT-d
> -     * engines: Snoop Control, DMA passthrough, Queued Invalidation and
> -     * Interrupt Remapping.
> +     * engines: Snoop Control, DMA passthrough, Queued Invalidation, Interrupt
> +     * Remapping, and Posted Interrupt
>       */
>      for_each_drhd_unit ( drhd )
>      {
> @@ -2176,6 +2179,14 @@ int __init intel_vtd_setup(void)
>          if ( iommu_intremap && !ecap_intr_remap(iommu->ecap) )
>              iommu_intremap = 0;
>  
> +        /*
> +         * We cannot use posted interrupt if X86_FEATURE_CX16 is
> +         * not supported, since we count on this feature to
> +         * atomically update 16-byte IRTE in posted format.
> +         */
> +        if ( !iommu_intremap || !cap_intr_post(iommu->cap) || !cpu_has_cx16 )
> +            iommu_intpost = 0;
> +
>          if ( !vtd_ept_page_compatible(iommu) )
>              iommu_hap_pt_share = 0;
>  
> @@ -2201,6 +2212,7 @@ int __init intel_vtd_setup(void)
>      P(iommu_passthrough, "Dom0 DMA Passthrough");
>      P(iommu_qinval, "Queued Invalidation");
>      P(iommu_intremap, "Interrupt Remapping");
> +    P(iommu_intpost, "Posted Interrupt");
>      P(iommu_hap_pt_share, "Shared EPT tables");
>  #undef P
>  
> @@ -2220,6 +2232,7 @@ int __init intel_vtd_setup(void)
>      iommu_passthrough = 0;
>      iommu_qinval = 0;
>      iommu_intremap = 0;
> +    iommu_intpost = 0;
>      return ret;
>  }
>  
> diff --git a/xen/drivers/passthrough/vtd/iommu.h b/xen/drivers/passthrough/vtd/iommu.h
> index ac71ed1..22abefe 100644
> --- a/xen/drivers/passthrough/vtd/iommu.h
> +++ b/xen/drivers/passthrough/vtd/iommu.h
> @@ -61,6 +61,7 @@
>  /*
>   * Decoding Capability Register
>   */
> +#define cap_intr_post(c)       (((c) >> 59) & 1)
>  #define cap_read_drain(c)      (((c) >> 55) & 1)
>  #define cap_write_drain(c)     (((c) >> 54) & 1)
>  #define cap_max_amask_val(c)   (((c) >> 48) & 0x3f)
> -- 
> 2.1.0
> 
> 
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