Re: [edk2-devel] [edk2-libc Patch 2 1/1] ek2-libc: wrmsr function available in edk2module is not working as expected

["Jayaprakash, N" <n.jayaprakash@intel.com>]

Thanks Mike as suggested made the logic simpler.
Sent the updated v3 patch for review.

Regards,
JP

-----Original Message-----
From: Kinney, Michael D <michael.d.kinney@intel.com> 
Sent: Friday, April 19, 2024 2:35 AM
To: Jayaprakash, N <n.jayaprakash@intel.com>; devel@edk2.groups.io
Cc: Rebecca Cran <rebecca@bsdio.com>; Kinney, Michael D <michael.d.kinney@intel.com>
Subject: RE: [edk2-libc Patch 2 1/1] ek2-libc: wrmsr function available in edk2module is not working as expected

The use of BitFieldOr64() is really only required when updating a portion of a 32-bit or 64-bit value that are not aligned on a 32-bit boundary and do not have a 32-bit aligned width.  Since this use case is setting the lower 32-bits, simpler logic should be used.

  data = LShiftU64(vedx, 32) | veax;

Mike

> -----Original Message-----
> From: Jayaprakash, N <n.jayaprakash@intel.com>
> Sent: Thursday, April 18, 2024 5:55 AM
> To: devel@edk2.groups.io
> Cc: Jayaprakash, N <n.jayaprakash@intel.com>; Rebecca Cran 
> <rebecca@bsdio.com>; Kinney, Michael D <michael.d.kinney@intel.com>
> Subject: [edk2-libc Patch 2 1/1] ek2-libc: wrmsr function available in 
> edk2module is not working as expected
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4745
> 
> This commit fixes the issue reported in the BZ4745.
> The wrmsr was always writing 0 to the higher 32 bits of the msr 
> register.
> This was due to a logical flaw in the code, where the input variable 
> of type unsigned int was left shitted by 32 bits without explicitly 
> converting it to a 64 bit value.
> 
> The issue is with the below statement.
> data = vedx << 32 | veax;
> Where the vedx which is an unsigned int, after left shifting by 32 
> bits its value will be set to 0. Because of this the higher 32 bits of 
> the MSR are always set to 0. This has been fixed by this commit.
> 
> Cc: Rebecca Cran <rebecca@bsdio.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Cc: Jayaprakash N <n.jayaprakash@intel.com>
> Signed-off-by: Jayaprakash N <n.jayaprakash@intel.com>
> ---
>  .../Python/Python-3.6.8/PyMod-3.6.8/Modules/edk2module.c       | 3
> ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/AppPkg/Applications/Python/Python-3.6.8/PyMod-
> 3.6.8/Modules/edk2module.c b/AppPkg/Applications/Python/Python-
> 3.6.8/PyMod-3.6.8/Modules/edk2module.c
> index 8786df8..06bcf82 100644
> --- a/AppPkg/Applications/Python/Python-3.6.8/PyMod-
> 3.6.8/Modules/edk2module.c
> +++ b/AppPkg/Applications/Python/Python-3.6.8/PyMod-
> 3.6.8/Modules/edk2module.c
> @@ -3886,7 +3886,8 @@ edk2_wrmsr(PyObject *self, PyObject *args)
>    UINT64       data = 0;
>    if (!PyArg_ParseTuple(args, "III", &vecx, &veax, &vedx))
>      return NULL;
> -  data = vedx << 32 | veax;
> +  data = LShiftU64(vedx, 32);
> +  data = BitFieldOr64(data, 0, 31, veax);
>    Py_BEGIN_ALLOW_THREADS
>    AsmWriteMsr64(vecx, data);
>    Py_END_ALLOW_THREADS
> --
> 2.44.0.windows.1



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