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

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

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On Mon, Mar 4, 2024 at 10:01 AM Laszlo Ersek <lersek@redhat.com> wrote:

> On 3/2/24 00:20, Tuan Phan wrote:
> > Thanks for the detailed review. Please see my comments below.
> >
> > On Fri, Mar 1, 2024 at 4:14 AM Laszlo Ersek <lersek@redhat.com
> > <mailto: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 <mailto:kraxel@redhat.com>>
> >     > Cc: Laszlo Ersek <lersek@redhat.com <mailto:lersek@redhat.com>>
> >     > Cc: Rahul Kumar <rahul1.kumar@intel.com
> >     <mailto:rahul1.kumar@intel.com>>
> >     > Cc: Ray Ni <ray.ni@intel.com <mailto:ray.ni@intel.com>>
> >     > Signed-off-by: Tuan Phan <tphan@ventanamicro.com
> >     <mailto: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
> >     <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.
>
> I would be curious how that can happen; to me a CacheTypeMask==0 input
> looks somewhat invalid.
>
> Either way, if such an input *is* valid, then there is a different
> problem with the patch: in the debug message we say that the cache type
> mask should contain *exactly one* bit set. That's not correct then: it
> should say *at most one* bit set. (Because the value 0 has 0 bits set,
> and apparently that is valid input.)
>
How about:  "More than one bit set in cache type mask" ? It is a clear
message that we don't expect
more than 1 bit set if not zero.

>
>
> >
> >
> >     > +  {
> >     > +    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.
>
> It's very strange. Do you know what your original code (the input to
> uncrustify) looked like? I wonder if uncrustify produces strange output
> if it sees unexpected input. Normally I wouldn't expect uncrustify to
> change the "((" format that I'm proposing. If it still does, then my
> request is invalid of course (uncrustify has priority, whatever it does).
>
I checked and it comes from an un-correct uncrustify version I used before.
It should be good now.

>
> Thanks!
> Laszlo
>
> >
> >
> >     For running uncrustify locally:
> >
> >     - clone
> >     <
> https://projectmu@dev.azure.com/projectmu/Uncrustify/_git/Uncrustify <
> 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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