Re: [edk2-devel] [PATCH v3 08/13] MdePkg/BaseLib: add support for RMPADJUST instruction

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

On 05/19/21 20:19, Brijesh Singh wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275
> 
> The RMPADJUST instruction will be used by the SEV-SNP guest to modify the
> RMP permissions for a guest page. See AMD APM volume 3 for further
> details.
> 
> 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: Laszlo Ersek <lersek@redhat.com>
> Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
>  MdePkg/Library/BaseLib/BaseLib.inf        |  1 +
>  MdePkg/Include/Library/BaseLib.h          | 35 ++++++++++++++++++++
>  MdePkg/Include/X64/Nasm.inc               |  8 +++++
>  MdePkg/Library/BaseLib/X64/RmpAdjust.nasm | 40 +++++++++++++++++++++++
>  4 files changed, 84 insertions(+)
>  create mode 100644 MdePkg/Library/BaseLib/X64/RmpAdjust.nasm
> 
> diff --git a/MdePkg/Library/BaseLib/BaseLib.inf b/MdePkg/Library/BaseLib/BaseLib.inf
> index 89a52f72c08a..6ccb8997b7e8 100644
> --- a/MdePkg/Library/BaseLib/BaseLib.inf
> +++ b/MdePkg/Library/BaseLib/BaseLib.inf
> @@ -319,6 +319,7 @@ [Sources.X64]
>    X64/DisablePaging64.nasm
>    X64/Pvalidate.nasm
>    X64/RdRand.nasm
> +  X64/RmpAdjust.nasm
>    X64/XGetBv.nasm
>    X64/XSetBv.nasm
>    X64/VmgExit.nasm
> diff --git a/MdePkg/Include/Library/BaseLib.h b/MdePkg/Include/Library/BaseLib.h
> index a2cd134bea9a..2452c1d92e51 100644
> --- a/MdePkg/Include/Library/BaseLib.h
> +++ b/MdePkg/Include/Library/BaseLib.h
> @@ -4861,6 +4861,41 @@ AsmPvalidate (
>    IN   BOOLEAN                 Validate,
>    IN   PHYSICAL_ADDRESS        Address
>    );
> +
> +//
> +// RDX settings for RMPADJUST
> +//
> +#define RMPADJUST_VMPL_MAX               3
> +#define RMPADJUST_VMPL_MASK              0xFF
> +#define RMPADJUST_VMPL_SHIFT             0
> +#define RMPADJUST_PERMISSION_MASK_MASK   0xFF
> +#define RMPADJUST_PERMISSION_MASK_SHIFT  8
> +#define RMPADJUST_VMSA_PAGE_BIT          BIT16
> +
> +/**
> +  Adjusts the permissions of an SEV-SNP guest page.
> +
> +  Executes a RMPADJUST instruction with the register state specified by Rax,
> +  Rcx, and Rdx. Returns Eax. This function is only available on X64.
> +
> +  The instruction is available only when CPUID Fn8000_001F_EAX[SNP]=1.
> +
> +  @param[in]  Rax   The value to load into RAX before executing the RMPADJUST
> +                    instruction.
> +  @param[in]  Rcx   The value to load into RCX before executing the RMPADJUST
> +                    instruction.
> +  @param[in]  Rdx   The value to load into RDX before executing the RMPADJUST
> +                    instruction.
> +
> +  @return     Eax

Thanks for fixing the Rax/Eax typo.

Laszlo

> +**/
> +UINT32
> +EFIAPI
> +AsmRmpAdjust (
> +  IN      UINT64                     Rax,
> +  IN      UINT64                     Rcx,
> +  IN      UINT64                     Rdx
> +  );
>  #endif
>  
>  
> diff --git a/MdePkg/Include/X64/Nasm.inc b/MdePkg/Include/X64/Nasm.inc
> index 528bb3385609..cfb14edc9449 100644
> --- a/MdePkg/Include/X64/Nasm.inc
> +++ b/MdePkg/Include/X64/Nasm.inc
> @@ -41,6 +41,14 @@
>      DB 0xF2, 0x0F, 0x01, 0xFF
>  %endmacro
>  
> +;
> +; Macro for the RMPADJUST instruction, defined in AMD APM volume 3.
> +; NASM feature request URL: https://bugzilla.nasm.us/show_bug.cgi?id=3392754
> +;
> +%macro RMPADJUST       0
> +    DB 0xF3, 0x0F, 0x01, 0xFE
> +%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/RmpAdjust.nasm b/MdePkg/Library/BaseLib/X64/RmpAdjust.nasm
> new file mode 100644
> index 000000000000..c307f64b518a
> --- /dev/null
> +++ b/MdePkg/Library/BaseLib/X64/RmpAdjust.nasm
> @@ -0,0 +1,40 @@
> +;-----------------------------------------------------------------------------
> +;
> +; Copyright (c) 2021, Advanced Micro Devices, Inc. All rights reserved.<BR>
> +; SPDX-License-Identifier: BSD-2-Clause-Patent
> +;
> +; Module Name:
> +;
> +;   RmpAdjust.Asm
> +;
> +; Abstract:
> +;
> +;   AsmRmpAdjust function
> +;
> +; Notes:
> +;
> +;-----------------------------------------------------------------------------
> +
> +%include "Nasm.inc"
> +
> +    SECTION .text
> +
> +;-----------------------------------------------------------------------------
> +;  UINT32
> +;  EFIAPI
> +;  AsmRmpAdjust (
> +;    IN  UINT64  Rax,
> +;    IN  UINT64  Rcx,
> +;    IN  UINT64  Rdx
> +;    )
> +;-----------------------------------------------------------------------------
> +global ASM_PFX(AsmRmpAdjust)
> +ASM_PFX(AsmRmpAdjust):
> +  mov     rax, rcx       ; Input Rax is in RCX by calling convention
> +  mov     rcx, rdx       ; Input Rcx is in RDX by calling convention
> +  mov     rdx, r8        ; Input Rdx is in R8  by calling convention
> +
> +  RMPADJUST
> +
> +  ; RMPADJUST returns the status in the EAX register.
> +  ret
>