Re: [edk2-devel] [PATCH v3 2/3] UefiCpuPkg: RISC-V: MMU: Support Svpbmt extension

["Tuan Phan" <tphan@ventanamicro.com>]

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Thanks for the detailed review. Please see my comments below.

On Fri, Mar 1, 2024 at 4:14 AM Laszlo Ersek <lersek@redhat.com> wrote:

> On 3/1/24 02:29, 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 | 101 +++++++++++++++---
> >  .../BaseRiscVMmuLib/BaseRiscVMmuLib.inf       |   1 +
> >  2 files changed, 88 insertions(+), 14 deletions(-)
> >
> > diff --git a/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.c
> b/UefiCpuPkg/Library/BaseRiscVMmuLib/BaseRiscVMmuLib.c
> > index 826a1d32a1d4..f4419bb8f380 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;
> > @@ -489,32 +494,89 @@ UpdateRegionMapping (
> >  /**
> >    Convert GCD attribute to RISC-V page attribute.
> >
> > -  @param  GcdAttributes The GCD attribute.
> > +  @param  GcdAttributes   The GCD attribute.
> > +  @param  RiscVAttribtues The pointer of RISC-V page attribute.
> >
> > -  @return               The RISC-V page attribute.
> > +  @retval EFI_INVALID_PARAMETER   The RiscVAttribtues is NULL or cache
> type mask not valid.
> > +  @retval EFI_SUCCESS             The operation succesfully.
> >
> >  **/
> >  STATIC
> > -UINTN
> > +EFI_STATUS
> >  GcdAttributeToPageAttribute (
> > -  IN UINTN  GcdAttributes
> > +  IN UINTN   GcdAttributes,
>
> Just noticing: why is GcdAttributes *not* UINT64 in the first place?
>
> All the bit macros we test against it, such as EFI_MEMORY_RO
> (0x0000000000020000ULL) are of type unsigned long long (UINT64).
>
Good catch. Will fix it.

>
> > +  OUT UINTN  *RiscVAttributes
> >    )
> >  {
> > -  UINTN  RiscVAttributes;
> > +  UINT64   CacheTypeMask;
> > +  BOOLEAN  PmbtExtEnabled = (PcdGet64 (PcdRiscVFeatureOverride) &
> RISCV_CPU_FEATURE_PBMT_BITMASK) ? TRUE : FALSE;
>
> - Per the edk2 coding style, locals should not be initialized (separate
> assignment is needed).
>
> - Bitmask checks always need an explicit comparison, such as
>
>   ((a & b) != 0)
>
> or similar. Implicitly interpreting (a & b) as a truth value is not
> appropriate.
>
> - "(whatever) ? TRUE : FALSE" is both bad style and unnecessary.
>
>   BOOLEAN  PmbtExtEnabled;
>
>   PmbtExtEnabled = (PcdGet64 (PcdRiscVFeatureOverride) &
>                     RISCV_CPU_FEATURE_PBMT_BITMASK) != 0;
>
> Will fix it.

> >
> > -  RiscVAttributes = RISCV_PG_R | RISCV_PG_W | RISCV_PG_X;
> > +  if (!RiscVAttributes) {
>
> - The coding style requires an explicit nullity check:
>
>   if (RiscVAttributes == NULL) {
>
Will fix it.

>
> > +    return EFI_INVALID_PARAMETER;
> > +  }
> > +
> > +  *RiscVAttributes = RISCV_PG_R | RISCV_PG_W | RISCV_PG_X;
> >
> >    // Determine protection attributes
> >    if ((GcdAttributes & EFI_MEMORY_RO) != 0) {
> > -    RiscVAttributes &= ~(RISCV_PG_W);
> > +    *RiscVAttributes &= ~(RISCV_PG_W);
> >    }
> >
> >    // Process eXecute Never attribute
> >    if ((GcdAttributes & EFI_MEMORY_XP) != 0) {
> > -    RiscVAttributes &= ~RISCV_PG_X;
> > +    *RiscVAttributes &= ~RISCV_PG_X;
> > +  }
> > +
>
> My next comment is unrelated to the patch, it's just something that
> catches my eye, and I think is worth fixing:
>
> RISCV_PG_W is BIT2 (0x00000004), and RISCV_PG_X is BIT3 (0x00000008).
> Meaning, they are of type *signed int* (INT32). Applying the bit-neg
> operator on them produces a negative value (because it flips the sign
> bit), which is very ugly.
>
> I suggest a separate patch for changing these into
>
>   ~(UINTN)RISCV_PG_W
>   ~(UINTN)RISCV_PG_X
>
> Alternatively, you could do
>
Will fix it in a separate patch along with the above change.

>
>   *RiscVAttributes = RISCV_PG_R;
>   if ((GcdAttributes & EFI_MEMORY_RO) == 0) {
>     *RiscVAttributes |= RISCV_PG_W;
>   }
>   if ((GcdAttributes & EFI_MEMORY_XP) == 0) {
>     *RiscVAttributes |= RISCV_PG_X;
>   }
>
> Either way: separate patch.
>
> > +  CacheTypeMask = GcdAttributes & EFI_CACHE_ATTRIBUTE_MASK;
> > +  if ((CacheTypeMask != 0) &&
> > +      (((CacheTypeMask - 1) & CacheTypeMask) != 0))
>
> This is not what I recommended in my previous review
> <https://edk2.groups.io/g/devel/message/115243>.
>
> Compare:
>
>   (CacheTypeMask != 0) && ...
>
> versus
>
>   (CacheTypeMask == 0) || ...
>
> Both of these ensure that the power-of-two check in the second
> subcondition (i.e., the subtraction of 1) is avoided when CacheTypeMask
> is zero. In the first variant, you get (FALSE && ...), in the second
> variant, you get (TRUE || ...); therefore, the power-of-two check is
> short-circuited for a zero input in both variants.
>
> However, considering the larger CacheTypeMask validation, your variant
> is incorrect, because a zero CacheTypeMask will ultimately evaluate the
> condition to FALSE -- (FALSE && ...) is FALSE --, and so the "return
> EFI_INVALID_PARAMETER" statement will not be reached. Whereas (TRUE ||
> ...) is TRUE, and so we return EFI_INVALID_PARAMETER for CacheTypeMask==0.
>
Actually the EDK2 passes (CacheTypeMask == 0) to this API during my debug
session.
Given that situation, this function doesn't do anything when CacheTypeMask
 == 0 so I think
it should not give the warning message.

>
> > +  {
> > +    DEBUG (
> > +      (
> > +       DEBUG_ERROR,
> > +       "%a: The cache type mask (0x%llX) should contain exactly one bit
> set\n",
>
> - Edk2's PrintLib does not use "ll" length modifiers. %u, %x and %X are
> for UINT32, and %lu, %lx and %lX are for UINT64. Furthermore, you may
> replace "l" with "L" freely.
>
Will fix it.

>
> - We generally group together the double parens for DEBUG invocations:
>
>   DEBUG ((
>     DEBUG_ERROR,
>     "%a: The cache type mask (0x%lX) ...\n",
>     __func__,
>     CacheTypeMask
>     ));
>
> > +       __func__,
> > +       CacheTypeMask
> > +      )
> > +      );
>
> The indentation of the closing parens is not correct either; please put
> your patches through uncrustify first. (CI will reject these issues
> anyway, in github pull requests.)
>
Actually this code is the result of uncrustify modification. Let me check
if anything
wrong with uncrustify.

>
> For running uncrustify locally:
>
> - clone
> <https://projectmu@dev.azure.com/projectmu/Uncrustify/_git/Uncrustify>
>
> - check it out at tag 73.0.8 (the tag that edk2 CI uses on github is in
> ".pytool/Plugin/UncrustifyCheck/uncrustify_ext_dep.yaml")
>
> - build it (IIRC it uses cmake)
>
> - with nothing dirty in the working tree (i.e., everything committed, or
> at least stashed to the index), run
>
>   uncrustify \
>     -c .pytool/Plugin/UncrustifyCheck/uncrustify.cfg \
>     --replace \
>     --no-backup \
>     --if-changed \
>     -F file-list.txt
>
> > +    return EFI_INVALID_PARAMETER;
> >    }
> >
> > -  return RiscVAttributes;
> > +  switch (CacheTypeMask) {
> > +    case EFI_MEMORY_UC:
> > +      if (PmbtExtEnabled) {
> > +        *RiscVAttributes |= PTE_PBMT_IO;
> > +      } else {
> > +        DEBUG (
> > +          (
> > +           DEBUG_VERBOSE,
> > +           "%a: EFI_MEMORY_UC set but Pmbt extension not available\n",
> > +           __func__
> > +          )
> > +          );
> > +      }
> > +
> > +      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 EFI_SUCCESS;
> >  }
> >
> >  /**
> > @@ -537,21 +599,32 @@ RiscVSetMemoryAttributes (
> >    IN UINTN                 Attributes
> >    )
> >  {
> > -  UINTN  PageAttributesSet;
> > +  UINTN       PageAttributesSet;
> > +  UINTN       PageAttributesClear;
> > +  EFI_STATUS  Status;
> >
> > -  PageAttributesSet = GcdAttributeToPageAttribute (Attributes);
> > +  Status = GcdAttributeToPageAttribute (Attributes, &PageAttributesSet);
> > +  if (EFI_ERROR (Status)) {
> > +    return Status;
> > +  }
> >
> >    if (!RiscVMmuEnabled ()) {
> >      return EFI_SUCCESS;
> >    }
> >
> > +  PageAttributesClear = PTE_ATTRIBUTES_MASK;
> > +  if ((PcdGet64 (PcdRiscVFeatureOverride) &
> RISCV_CPU_FEATURE_PBMT_BITMASK) != 0) {
> > +    PageAttributesClear |= PTE_PBMT_MASK;
> > +  }
> > +
> >    DEBUG (
> >      (
> >       DEBUG_VERBOSE,
> > -     "%a: Set %llX page attribute 0x%X\n",
> > +     "%a: %llX: set attributes 0x%X, clear attributes 0x%X\n",
> >       __func__,
> >       BaseAddress,
> > -     PageAttributesSet
> > +     PageAttributesSet,
> > +     PageAttributesClear
> >      )
> >      );
>
> - UINT64 should be formatted with %[Ll][uxX].
>
> - UINT32 should be formatted with %[uxX].
>
> - UINTN is trickier, there is no dedicated conversion specifier. The
> portable solution (between 32-bit and 64-bit platforms in edk2) is to
> (a) cast the UINTN value to UINT64, (b) format the latter with %[Ll][uxX].
>
> So you need something like
>
>   DEBUG ((
>     DEBUG_VERBOSE,
>     "%a: %LX: set attributes 0x%LX, clear attributes 0x%LX\n",
>     __func__,
>     BaseAddress,                // this is UINT64
>     (UINT64)PageAttributesSet,  // originally UINTN
>     (UINT64)PageAttributesClear // originally UINTN
>     ));
>
Thanks for the suggestion. Will fix it.

>
> >
> > @@ -559,7 +632,7 @@ RiscVSetMemoryAttributes (
> >             BaseAddress,
> >             Length,
> >             PageAttributesSet,
> > -           PTE_ATTRIBUTES_MASK,
> > +           PageAttributesClear,
> >             (UINTN *)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
>
> Laszlo
>
>


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