linux-kernel - Re: [PATCH] KVM: TDX: Don't report base TDVMCALLs

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Message-ID: <f0281c2f-4ddf-4a0c-81a2-b6de51a4fe82@linux.intel.com>
Date: Thu, 17 Jul 2025 10:45:56 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Xiaoyao Li <xiaoyao.li@...el.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>,
 Sean Christopherson <seanjc@...gle.com>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: TDX: Don't report base TDVMCALLs



On 7/17/2025 10:20 AM, Xiaoyao Li wrote:
> Remove TDVMCALLINFO_GET_QUOTE from user_tdvmcallinfo_1_r11 reported to
> userspace to align with the direction of the GHCI spec.
>
> Recently, concern was raised about a gap in the GHCI spec that left
> ambiguity in how to expose to the guest that only a subset of GHCI
> TDVMCalls were supported. During the back and forth on the spec details[0],
> <GetQuote> was moved from an individually enumerable TDVMCall, to one that
> is part of the 'base spec', meaning it doesn't have a specific bit in the

'GHCI base API' is more appropriate instead of 'base spec'

> <GetTDVMCallInfo> return values. Although the spec[1] is still in draft
> form, the GetQoute part has been agreed by the major TDX VMMs.
GetQoute  ->  <GetQuote>

typo and use <> to align with others.

>
> Unfortunately the commits that were upstreamed still treat <GetQuote> as
> individually enumerable. They set bit 0 in the user_tdvmcallinfo_1_r11
> which is reported to userspace to tell supported optional TDVMCalls,
> intending to say that <GetQuote> is supported.
>
> So stop reporting <GetQute> in user_tdvmcallinfo_1_r11 to align with

GetQute -> GetQuote

> the direction of the spec, and allow some future TDVMCall to use that bit.
>
> [0] https://lore.kernel.org/all/aEmuKII8FGU4eQZz@google.com/
> [1] https://cdrdv2.intel.com/v1/dl/getContent/858626
>
> Fixes: 28224ef02b56 ("KVM: TDX: Report supported optional TDVMCALLs in TDX capabilities")
> Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>

Nits: typos and wording suggested above.

Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>

> ---
>   arch/x86/kvm/vmx/tdx.c | 2 --
>   1 file changed, 2 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index f31ccdeb905b..ea1261ca805f 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -173,7 +173,6 @@ static void td_init_cpuid_entry2(struct kvm_cpuid_entry2 *entry, unsigned char i
>   	tdx_clear_unsupported_cpuid(entry);
>   }
>   
> -#define TDVMCALLINFO_GET_QUOTE				BIT(0)
>   #define TDVMCALLINFO_SETUP_EVENT_NOTIFY_INTERRUPT	BIT(1)
>   
>   static int init_kvm_tdx_caps(const struct tdx_sys_info_td_conf *td_conf,
> @@ -192,7 +191,6 @@ static int init_kvm_tdx_caps(const struct tdx_sys_info_td_conf *td_conf,
>   	caps->cpuid.nent = td_conf->num_cpuid_config;
>   
>   	caps->user_tdvmcallinfo_1_r11 =
> -		TDVMCALLINFO_GET_QUOTE |
>   		TDVMCALLINFO_SETUP_EVENT_NOTIFY_INTERRUPT;
>   
>   	for (i = 0; i < td_conf->num_cpuid_config; i++)