Re: [edk2-devel] [PATCH v2 07/13] MdePkg/BaseLib: add support for PVALIDATE instruction

["Laszlo Ersek" <lersek@redhat.com>]

On 05/13/21 01:46, Brijesh Singh wrote:
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275
> 
> The PVALIDATE instruction validates or rescinds validation of a guest
> page RMP entry. Upon completion, a return code is stored in EAX, rFLAGS
> bits OF, ZF, AF, PF and SF are set based on this return code. If the
> instruction completed succesfully, the rFLAGS bit CF indicates if the
> contents of the RMP entry were changed or not.
> 
> For more information about the instruction see AMD APM volume 3.
> 
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: Michael D Kinney <michael.d.kinney@intel.com>
> Cc: Liming Gao <gaoliming@byosoft.com.cn>
> Cc: Zhiguang Liu <zhiguang.liu@intel.com>
> Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  MdePkg/Library/BaseLib/BaseLib.inf        |  1 +
>  MdePkg/Include/Library/BaseLib.h          | 50 +++++++++++++++++++++++
>  MdePkg/Include/X64/Nasm.inc               |  8 ++++
>  MdePkg/Library/BaseLib/X64/Pvalidate.nasm | 42 +++++++++++++++++++
>  4 files changed, 101 insertions(+)
>  create mode 100644 MdePkg/Library/BaseLib/X64/Pvalidate.nasm

Many thanks for the updates!

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo

> 
> diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
> index b76f3af380ea..89a52f72c08a 100644
> --- a/MdePkg/Library/BaseLib/BaseLib.inf
> +++ b/MdePkg/Library/BaseLib/BaseLib.inf
> @@ -317,6 +317,7 @@ [Sources.X64]
>    X64/GccInlinePriv.c | GCC
>    X64/EnableDisableInterrupts.nasm
>    X64/DisablePaging64.nasm
> +  X64/Pvalidate.nasm
>    X64/RdRand.nasm
>    X64/XGetBv.nasm
>    X64/XSetBv.nasm
> diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h
> index 7253997a6f8c..a2cd134bea9a 100644
> --- a/MdePkg/Include/Library/BaseLib.h
> +++ b/MdePkg/Include/Library/BaseLib.h
> @@ -4813,6 +4813,56 @@ SpeculationBarrier (
>    VOID
>    );
>  
> +#if defined (MDE_CPU_X64)
> +//
> +// The page size for the PVALIDATE instruction
> +//
> +typedef enum {
> +  PvalidatePageSize4K = 0,
> +  PvalidatePageSize2MB,
> +} PVALIDATE_PAGE_SIZE;
> +
> +//
> +// PVALIDATE Return Code.
> +//
> +#define PVALIDATE_RET_SUCCESS         0
> +#define PVALIDATE_RET_FAIL_INPUT      1
> +#define PVALIDATE_RET_SIZE_MISMATCH   6
> +
> +//
> +// The PVALIDATE instruction did not make any changes to the RMP entry.
> +//
> +#define PVALIDATE_RET_NO_RMPUPDATE    255
> +
> +/**
> + Execute a PVALIDATE instruction to validate or to rescinds validation of a guest
> + page's RMP entry.
> +
> + The instruction is available only when CPUID Fn8000_001F_EAX[SNP]=1.
> +
> + The function is available on X64.
> +
> + @param[in]    PageSize         The page size to use.
> + @param[in]    Validate         If TRUE, validate the guest virtual address
> +                                otherwise invalidate the guest virtual address.
> + @param[in]    Address          The guest virtual address.
> +
> + @retval PVALIDATE_RET_SUCCESS        The PVALIDATE instruction succeeded, and
> +                                      updated the RMP entry.
> + @retval PVALIDATE_RET_NO_RMPUPDATE   The PVALIDATE instruction succeeded, but
> +                                      did not update the RMP entry.
> + @return                              Failure code from the PVALIDATE
> +                                      instruction.
> +**/
> +UINT32
> +EFIAPI
> +AsmPvalidate (
> +  IN   PVALIDATE_PAGE_SIZE     PageSize,
> +  IN   BOOLEAN                 Validate,
> +  IN   PHYSICAL_ADDRESS        Address
> +  );
> +#endif
> +
>  
>  #if defined (MDE_CPU_IA32) || defined (MDE_CPU_X64)
>  ///
> diff --git a/MdePkg/Include/X64/Nasm.inc b/MdePkg/Include/X64/Nasm.inc
> index 527f71e9eb4d..528bb3385609 100644
> --- a/MdePkg/Include/X64/Nasm.inc
> +++ b/MdePkg/Include/X64/Nasm.inc
> @@ -33,6 +33,14 @@
>      DB 0xF3, 0x48, 0x0F, 0xAE, 0xE8
>  %endmacro
>  
> +;
> +; Macro for the PVALIDATE instruction, defined in AMD APM volume 3.
> +; NASM feature request URL: https://bugzilla.nasm.us/show_bug.cgi?id=3392753
> +;
> +%macro PVALIDATE       0
> +    DB 0xF2, 0x0F, 0x01, 0xFF
> +%endmacro
> +
>  ; NASM provides built-in macros STRUC and ENDSTRUC for structure definition.
>  ; For example, to define a structure called mytype containing a longword,
>  ; a word, a byte and a string of bytes, you might code
> diff --git a/MdePkg/Library/BaseLib/X64/Pvalidate.nasm b/MdePkg/Library/BaseLib/X64/Pvalidate.nasm
> new file mode 100644
> index 000000000000..a7d177913405
> --- /dev/null
> +++ b/MdePkg/Library/BaseLib/X64/Pvalidate.nasm
> @@ -0,0 +1,42 @@
> +;-----------------------------------------------------------------------------
> +;
> +; Copyright (c) 2021, AMD. All rights reserved.<BR>
> +; SPDX-License-Identifier: BSD-2-Clause-Patent
> +;
> +;-----------------------------------------------------------------------------
> +
> +%include "Nasm.inc"
> +
> +    SECTION .text
> +
> +;-----------------------------------------------------------------------------
> +;  UINT32
> +;  EFIAPI
> +;  AsmPvalidate (
> +;    IN   UINT32              PageSize
> +;    IN   UINT32              Validate,
> +;    IN   UINT64              Address
> +;    )
> +;-----------------------------------------------------------------------------
> +global ASM_PFX(AsmPvalidate)
> +ASM_PFX(AsmPvalidate):
> +  mov     rax, r8
> +
> +  PVALIDATE
> +
> +  ; Save the carry flag.
> +  setc    dl
> +
> +  ; The PVALIDATE instruction returns the status in rax register.
> +  cmp     rax, 0
> +  jne     PvalidateExit
> +
> +  ; Check the carry flag to determine if RMP entry was updated.
> +  cmp     dl, 0
> +  je      PvalidateExit
> +
> +  ; Return the PVALIDATE_RET_NO_RMPUPDATE.
> +  mov     rax, 255
> +
> +PvalidateExit:
> +  ret
>