Re: [Xen-devel] [PATCH 2/2] x86/SVM-IOMMU: Drop get_field_from_byte()

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: 24 September 2018 11:56
> To: Xen-devel <xen-devel@xxxxxxxxxxxxx>
> Cc: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>; Jan Beulich
> <JBeulich@xxxxxxxx>; Wei Liu <wei.liu2@xxxxxxxxxx>; Roger Pau Monne
> <roger.pau@xxxxxxxxxx>; Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Suravee
> Suthikulpanit <suravee.suthikulpanit@xxxxxxx>; Brian Woods
> <brian.woods@xxxxxxx>
> Subject: [PATCH 2/2] x86/SVM-IOMMU: Drop get_field_from_byte()
> 
> It is MASK_EXTR() in disguise, but less flexible.
> 
> No functional change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

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

> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Paul Durrant <paul.durrant@xxxxxxxxxx>
> CC: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
> CC: Brian Woods <brian.woods@xxxxxxx>
> ---
>  xen/drivers/passthrough/amd/iommu_map.c       | 2 +-
>  xen/include/asm-x86/hvm/svm/amd-iommu-proto.h | 5 -----
>  2 files changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/xen/drivers/passthrough/amd/iommu_map.c
> b/xen/drivers/passthrough/amd/iommu_map.c
> index 70b4345..ded2cc7 100644
> --- a/xen/drivers/passthrough/amd/iommu_map.c
> +++ b/xen/drivers/passthrough/amd/iommu_map.c
> @@ -220,7 +220,7 @@ void __init iommu_dte_add_device_entry(u32 *dte,
> struct ivrs_mappings *ivrs_dev)
>      dte[7] = dte[6] = dte[4] = dte[2] = dte[1] = dte[0] = 0;
> 
>      flags = ivrs_dev->device_flags;
> -    sys_mgt = get_field_from_byte(flags, ACPI_IVHD_SYSTEM_MGMT);
> +    sys_mgt = MASK_EXTR(flags, ACPI_IVHD_SYSTEM_MGMT);
>      dev_ex = ivrs_dev->dte_allow_exclusion;
> 
>      flags &= mask;
> diff --git a/xen/include/asm-x86/hvm/svm/amd-iommu-proto.h
> b/xen/include/asm-x86/hvm/svm/amd-iommu-proto.h
> index 99bc21c..1b965e1 100644
> --- a/xen/include/asm-x86/hvm/svm/amd-iommu-proto.h
> +++ b/xen/include/asm-x86/hvm/svm/amd-iommu-proto.h
> @@ -155,11 +155,6 @@ static inline u32 set_field_in_reg_u32(u32 field, u32
> reg_value,
>      return reg_value;
>  }
> 
> -static inline u8 get_field_from_byte(u8 value, u8 mask)
> -{
> -    return (value & mask) / (mask & -mask);
> -}
> -
>  static inline unsigned long region_to_pages(unsigned long addr, unsigned
> long size)
>  {
>      return (PAGE_ALIGN(addr + size) - (addr & PAGE_MASK)) >> PAGE_SHIFT;
> --
> 2.1.4

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