Re: [edk2-devel] [PATCH v4 3/4] UefiCpuPkg: RISC-V: MMU: Support Svpbmt extension

["Sunil V L" <sunilvl@ventanamicro.com>]

Hi Tuan,

On Thu, Mar 14, 2024 at 01:19:16PM -0700, Tuan Phan wrote:
> The GCD EFI_MEMORY_UC and EFI_MEMORY_WC memory attributes will be
> supported when Svpbmt extension available.
> 
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Signed-off-by: Tuan Phan <tphan@ventanamicro.com>
> ---
>  .../Library/BaseRiscVMmuLib/BaseRiscVMmuLib.c | 106 ++++++++++++++----
>  .../BaseRiscVMmuLib/BaseRiscVMmuLib.inf       |   1 +
>  2 files changed, 86 insertions(+), 21 deletions(-)
> 
> diff --git a/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.c b/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.c
> index 46ba4b4709b1..34300dca5c34 100644
> --- a/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.c
> +++ b/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.c
> @@ -36,6 +36,11 @@
>  #define PTE_PPN_SHIFT         10
>  #define RISCV_MMU_PAGE_SHIFT  12
>  
> +#define RISCV_CPU_FEATURE_PBMT_BITMASK  BIT2
> +#define PTE_PBMT_NC                     BIT61
> +#define PTE_PBMT_IO                     BIT62
> +#define PTE_PBMT_MASK                   (PTE_PBMT_NC | PTE_PBMT_IO)
> +
>  STATIC UINTN  mModeSupport[] = { SATP_MODE_SV57, SATP_MODE_SV48, SATP_MODE_SV39, SATP_MODE_OFF };
>  STATIC UINTN  mMaxRootTableLevel;
>  STATIC UINTN  mBitPerLevel;
> @@ -487,32 +492,82 @@ UpdateRegionMapping (
>  /**
>    Convert GCD attribute to RISC-V page attribute.
>  
> -  @param  GcdAttributes The GCD attribute.
> +  @param  GcdAttributes   The GCD attribute.
> +  @param  RiscVAttributes The pointer of RISC-V page attribute.
>  
> -  @return               The RISC-V page attribute.
> +  @retval EFI_INVALID_PARAMETER   The RiscVAttributes is NULL or cache type mask not valid.
> +  @retval EFI_SUCCESS             The operation succesfully.
>  
>  **/
>  STATIC
> -UINT64
> +EFI_STATUS
>  GcdAttributeToPageAttribute (
> -  IN UINT64  GcdAttributes
> +  IN UINT64   GcdAttributes,
> +  OUT UINT64  *RiscVAttributes
>    )
>  {
> -  UINT64  RiscVAttributes;
> +  UINT64   CacheTypeMask;
> +  BOOLEAN  PmbtExtEnabled;
>  
Why not read the PCD once and save in a static variable?

> -  RiscVAttributes = RISCV_PG_R | RISCV_PG_W | RISCV_PG_X;
> +  if (RiscVAttributes == NULL) {
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  *RiscVAttributes = RISCV_PG_R | RISCV_PG_W | RISCV_PG_X;
> +
> +  PmbtExtEnabled = FALSE;
> +  if ((PcdGet64 (PcdRiscVFeatureOverride) & RISCV_CPU_FEATURE_PBMT_BITMASK) != 0) {
> +    PmbtExtEnabled = TRUE;
> +  }
>  
>    // Determine protection attributes
>    if ((GcdAttributes & EFI_MEMORY_RO) != 0) {
> -    RiscVAttributes &= ~(UINT64)(RISCV_PG_W);
> +    *RiscVAttributes &= ~(UINT64)(RISCV_PG_W);
>    }
>  
>    // Process eXecute Never attribute
>    if ((GcdAttributes & EFI_MEMORY_XP) != 0) {
> -    RiscVAttributes &= ~(UINT64)RISCV_PG_X;
> +    *RiscVAttributes &= ~(UINT64)RISCV_PG_X;
> +  }
> +
> +  CacheTypeMask = GcdAttributes & EFI_CACHE_ATTRIBUTE_MASK;
> +  if ((CacheTypeMask != 0) &&
> +      (((CacheTypeMask - 1) & CacheTypeMask) != 0))
> +  {
> +    DEBUG ((
> +      DEBUG_ERROR,
> +      "%a: More than one bit set in cache type mask (0x%LX)\n",
> +      __func__,
> +      CacheTypeMask
> +      ));
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  switch (CacheTypeMask) {
> +    case EFI_MEMORY_UC:
> +      if (PmbtExtEnabled) {
> +        *RiscVAttributes |= PTE_PBMT_IO;
> +      }
> +
> +      break;
> +    case EFI_MEMORY_WC:
> +      if (PmbtExtEnabled) {
> +        *RiscVAttributes |= PTE_PBMT_NC;
> +      } else {
> +        DEBUG ((
> +          DEBUG_VERBOSE,
> +          "%a: EFI_MEMORY_WC set but Pmbt extension not available\n",
> +          __func__
> +          ));
> +      }
> +
> +      break;
> +    default:
> +      // Default PMA mode
> +      break;
>    }
>  
> -  return RiscVAttributes;
> +  return EFI_SUCCESS;
>  }
>  
>  /**
> @@ -535,29 +590,38 @@ RiscVSetMemoryAttributes (
>    IN UINT64                Attributes
>    )
>  {
> -  UINT64  PageAttributesSet;
> +  UINT64      PageAttributesSet;
> +  UINT64      PageAttributesClear;
> +  EFI_STATUS  Status;
>  
> -  PageAttributesSet = GcdAttributeToPageAttribute (Attributes);
> +  Status = GcdAttributeToPageAttribute (Attributes, &PageAttributesSet);
> +  if (EFI_ERROR (Status)) {
> +    return Status;
> +  }
>
Is there a reason to do this prior to checking RiscVMmuEnabled()?

>    if (!RiscVMmuEnabled ()) {
>      return EFI_SUCCESS;
>    }
>  
> -  DEBUG (
> -    (
> -     DEBUG_VERBOSE,
> -     "%a: Set %llX page attribute 0x%X\n",
> -     __func__,
> -     BaseAddress,
> -     PageAttributesSet
> -    )
> -    );
> +  PageAttributesClear = PTE_ATTRIBUTES_MASK;
> +  if ((PcdGet64 (PcdRiscVFeatureOverride) & RISCV_CPU_FEATURE_PBMT_BITMASK) != 0) {
> +    PageAttributesClear |= PTE_PBMT_MASK;
> +  }
> +
I think static variable would be better.

> +  DEBUG ((
> +    DEBUG_VERBOSE,
> +    "%a: %LX: set attributes 0x%LX, clear attributes 0x%LX\n",
> +    __func__,
> +    BaseAddress,
> +    PageAttributesSet,
> +    PageAttributesClear
> +    ));
>  
>    return UpdateRegionMapping (
>             BaseAddress,
>             Length,
>             PageAttributesSet,
> -           PTE_ATTRIBUTES_MASK,
> +           PageAttributesClear,
>             (UINT64 *)RiscVGetRootTranslateTable (),
>             TRUE
>             );
> diff --git a/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.inf b/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.inf
> index 51ebe1750e97..1dbaa81f3608 100644
> --- a/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.inf
> +++ b/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.inf
> @@ -28,3 +28,4 @@
>  
>  [Pcd]
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuRiscVMmuMaxSatpMode  ## CONSUMES
> +  gEfiMdePkgTokenSpaceGuid.PcdRiscVFeatureOverride     ## CONSUMES
> -- 
> 2.25.1
> 


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