linux-kernel - RE: [PATCH v3 08/10] x86/hyperv: Use TDX GHCI to access some MSRs in a TDX VM with the paravisor

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Message-ID: <BYAPR21MB1688B8B8FBFA32065B08D0B7D71DA@BYAPR21MB1688.namprd21.prod.outlook.com>
Date:   Thu, 24 Aug 2023 14:08:35 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Dexuan Cui <decui@...rosoft.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "arnd@...db.de" <arnd@...db.de>, "bp@...en8.de" <bp@...en8.de>,
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        Haiyang Zhang <haiyangz@...rosoft.com>,
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        KY Srinivasan <kys@...rosoft.com>,
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CC:     "x86@...nel.org" <x86@...nel.org>,
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Subject: RE: [PATCH v3 08/10] x86/hyperv: Use TDX GHCI to access some MSRs in
 a TDX VM with the paravisor

From: Dexuan Cui <decui@...rosoft.com> Sent: Thursday, August 24, 2023 1:07 AM
> 
> When the paravisor is present, a SNP VM must use GHCB to access some
> special MSRs, including HV_X64_MSR_GUEST_OS_ID and some SynIC MSRs.
> 
> Similarly, when the paravisor is present, a TDX VM must use TDX GHCI
> to access the same MSRs.
> 
> Implement hv_tdx_msr_write() and hv_tdx_msr_read(), and use the helper
> functions hv_ivm_msr_read() and hv_ivm_msr_write() to access the MSRs
> in a unified way for SNP/TDX VMs with the paravisor.
> 
> Do not export hv_tdx_msr_write() and hv_tdx_msr_read(), because we never
> really used hv_ghcb_msr_write() and hv_ghcb_msr_read() in any module.
> 
> Update arch/x86/include/asm/mshyperv.h so that the kernel can still build
> if CONFIG_AMD_MEM_ENCRYPT or CONFIG_INTEL_TDX_GUEST is not set, or
> neither is set.
> 
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> ---
> 
> Changes in v2: None
> 
> Changes in v3:
>   hv_tdx_read_msr -> hv_tdx_msr_read
>   hv_tdx_write_msr -> hv_tdx_msr_write
>   Do not export hv_tdx_msr_write() and hv_tdx_msr_read().
>   included <uapi/asm/vmx.h>
>   Updated arch/x86/include/asm/mshyperv.h so that the kernel
>     can still build if CONFIG_AMD_MEM_ENCRYPT and/or
>     CONFIG_INTEL_TDX_GUEST are not set.
> 
>  arch/x86/hyperv/hv_init.c       |  8 ++--
>  arch/x86/hyperv/ivm.c           | 69 +++++++++++++++++++++++++++++++--
>  arch/x86/include/asm/mshyperv.h |  8 ++--
>  arch/x86/kernel/cpu/mshyperv.c  |  8 ++--
>  4 files changed, 77 insertions(+), 16 deletions(-)

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>