linux-kernel - Re: [RFC PATCH v2 15/18] KVM: TDX: Combine KVM_BUG_ON + pr_tdx_error() into TDX_BUG

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Message-ID: <4b1fe5da252b186f0ad4715c46f32e18b735a9bf.camel@intel.com>
Date: Tue, 2 Sep 2025 18:55:06 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "pbonzini@...hat.com" <pbonzini@...hat.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>
CC: "Huang, Kai" <kai.huang@...el.com>, "ackerleytng@...gle.com"
	<ackerleytng@...gle.com>, "Annapurve, Vishal" <vannapurve@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Zhao, Yan Y"
	<yan.y.zhao@...el.com>, "Weiny, Ira" <ira.weiny@...el.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, "michael.roth@....com"
	<michael.roth@....com>
Subject: Re: [RFC PATCH v2 15/18] KVM: TDX: Combine KVM_BUG_ON +
 pr_tdx_error() into TDX_BUG_ON()

On Thu, 2025-08-28 at 17:06 -0700, Sean Christopherson wrote:
> Add TDX_BUG_ON() macros (with varying numbers of arguments) to deduplicate
> the myriad flows that do KVM_BUG_ON()/WARN_ON_ONCE() followed by a call to
> pr_tdx_error().  In addition to reducing boilerplate copy+paste code, this
> also helps ensure that KVM provides consistent handling of SEAMCALL errors.
> 
> Opportunistically convert a handful of bare WARN_ON_ONCE() paths to the
> equivalent of KVM_BUG_ON(), i.e. have them terminate the VM.  If a SEAMCALL
> error is fatal enough to WARN on, it's fatal enough to terminate the TD.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/vmx/tdx.c | 114 +++++++++++++++++------------------------
>  1 file changed, 47 insertions(+), 67 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index aa6d88629dae..df9b4496cd01 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -24,20 +24,32 @@
>  #undef pr_fmt
>  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>  
> -#define pr_tdx_error(__fn, __err)	\
> -	pr_err_ratelimited("SEAMCALL %s failed: 0x%llx\n", #__fn, __err)
> +#define __TDX_BUG_ON(__err, __f, __kvm, __fmt, __args...)			\
> +({										\
> +	struct kvm *_kvm = (__kvm);						\
> +	bool __ret = !!(__err);							\
> +										\
> +	if (WARN_ON_ONCE(__ret && (!_kvm || !_kvm->vm_bugged))) {		\
> +		if (_kvm)							\
> +			kvm_vm_bugged(_kvm);					\
> +		pr_err_ratelimited("SEAMCALL " __f " failed: 0x%llx" __fmt "\n",\
> +				   __err,  __args);				\
> +	}									\
> +	unlikely(__ret);							\
> +})
>  
> -#define __pr_tdx_error_N(__fn_str, __err, __fmt, ...)		\
> -	pr_err_ratelimited("SEAMCALL " __fn_str " failed: 0x%llx, " __fmt,  __err,  __VA_ARGS__)
> +#define TDX_BUG_ON(__err, __fn, __kvm)				\
> +	__TDX_BUG_ON(__err, #__fn, __kvm, "%s", "")
>  
> -#define pr_tdx_error_1(__fn, __err, __rcx)		\
> -	__pr_tdx_error_N(#__fn, __err, "rcx 0x%llx\n", __rcx)
> +#define TDX_BUG_ON_1(__err, __fn, __rcx, __kvm)			\
> +	__TDX_BUG_ON(__err, #__fn, __kvm, ", rcx 0x%llx", __rcx)
>  
> -#define pr_tdx_error_2(__fn, __err, __rcx, __rdx)	\
> -	__pr_tdx_error_N(#__fn, __err, "rcx 0x%llx, rdx 0x%llx\n", __rcx, __rdx)
> +#define TDX_BUG_ON_2(__err, __fn, __rcx, __rdx, __kvm)		\
> +	__TDX_BUG_ON(__err, #__fn, __kvm, ", rcx 0x%llx, rdx 0x%llx", __rcx, __rdx)
> +
> +#define TDX_BUG_ON_3(__err, __fn, __rcx, __rdx, __r8, __kvm)	\
> +	__TDX_BUG_ON(__err, #__fn, __kvm, ", rcx 0x%llx, rdx 0x%llx, r8 0x%llx", __rcx, __rdx, __r8)
>  
> -#define pr_tdx_error_3(__fn, __err, __rcx, __rdx, __r8)	\
> -	__pr_tdx_error_N(#__fn, __err, "rcx 0x%llx, rdx 0x%llx, r8 0x%llx\n", __rcx, __rdx, __r8)

Having each TDX_BUG_ON() individually do #__fn is extra code today, but it
leaves __TDX_BUG_ON() usable for custom special TDX_BUG_ON()'s later.

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>