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

["Michael D Kinney" <michael.d.kinney@intel.com>]

> -----Original Message-----
> From: Jayaprakash, N <n.jayaprakash@intel.com>
> Sent: Tuesday, April 9, 2024 11:09 PM
> To: devel@edk2.groups.io; Jayaprakash, N <n.jayaprakash@intel.com>
> Cc: Rebecca Cran <rebecca@bsdio.com>; Kinney, Michael D
> <michael.d.kinney@intel.com>
> Subject: RE: [edk2-devel] [edk2-libc Patch 1/1] edk2-libc: wrmsr
> function available in edk2module is not working as expected
> 
> Reviewed-by : Jayaprakash N
> 
> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of
> Jayaprakash, N
> Sent: Thursday, April 4, 2024 3:14 PM
> 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-devel] [edk2-libc Patch 1/1] edk2-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 function 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 to a 64 bit value.
> 
> Problematic statement in the function edk2_wrmsr code:
> data = vedx << 32 | veax;
> Where the vedx 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 statement has been modified as below:
>   data = (((UINT64)vedx) << 32) | veax;
> Verified the function by making this change and could see that the
> wrmsr is working as expected.
> 
> 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        | 2
> +-
>  1 file changed, 1 insertion(+), 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 d6af8da..cec4332 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/edk2mo
> +++ dule.c
> @@ -3886,7 +3886,7 @@ edk2_wrmsr(PyObject *self, PyObject *args)
>    UINT64       data = 0;
>    if (!PyArg_ParseTuple(args, "III", &vecx, &veax, &vedx))
>      return NULL;
> -  data = vedx << 32 | veax;
> +  data = (((UINT64)vedx) << 32) | veax;

On 32-bit builds, this will use an intrinsic.  Is BaseLib LShiftU64() available here?

>    Py_BEGIN_ALLOW_THREADS
>    AsmWriteMsr64(vecx, data);
>    Py_END_ALLOW_THREADS
> --
> 2.40.0.windows.1
> 
> 
> 
> 
> 



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