linux-kernel - Re: [PATCH v8 03/30] KVM: selftests: Store initial stack address in struct kvm

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Message-ID: <aJoyiVlz1cxgW7Xm@google.com>
Date: Mon, 11 Aug 2025 11:12:25 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sagi Shahar <sagis@...gle.com>
Cc: linux-kselftest@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>, 
	Shuah Khan <shuah@...nel.org>, Ackerley Tng <ackerleytng@...gle.com>, 
	Ryan Afranji <afranji@...gle.com>, Andrew Jones <ajones@...tanamicro.com>, 
	Isaku Yamahata <isaku.yamahata@...el.com>, Erdem Aktas <erdemaktas@...gle.com>, 
	Rick Edgecombe <rick.p.edgecombe@...el.com>, Roger Wang <runanwang@...gle.com>, 
	Binbin Wu <binbin.wu@...ux.intel.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	"Pratik R. Sampat" <pratikrajesh.sampat@....com>, Reinette Chatre <reinette.chatre@...el.com>, 
	Ira Weiny <ira.weiny@...el.com>, linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v8 03/30] KVM: selftests: Store initial stack address in
 struct kvm_vcpu

On Thu, Aug 07, 2025, Sagi Shahar wrote:
> From: Ackerley Tng <ackerleytng@...gle.com>
> 
> TDX guests' registers cannot be initialized directly using
> vcpu_regs_set(), hence the stack pointer needs to be initialized by
> the guest itself, running boot code beginning at the reset vector.
> 
> Store the stack address as part of struct kvm_vcpu so that it can
> be accessible later to be passed to the boot code for rsp
> initialization.

NAK.  This bleeds x86 details into common code, and is again a convoluted way of
passing information into TDX specific code.

> 
> Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
> Signed-off-by: Sagi Shahar <sagis@...gle.com>
> ---
>  tools/testing/selftests/kvm/include/kvm_util.h  | 1 +
>  tools/testing/selftests/kvm/lib/x86/processor.c | 2 ++
>  2 files changed, 3 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
> index 9994861d2acb..5c4ca25803ac 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> @@ -58,6 +58,7 @@ struct kvm_vcpu {
>  	int fd;
>  	struct kvm_vm *vm;
>  	struct kvm_run *run;
> +	vm_vaddr_t initial_stack_addr;
>  #ifdef __x86_64__
>  	struct kvm_cpuid2 *cpuid;
>  #endif
> diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
> index 002303e2a572..da6e9315ebe2 100644
> --- a/tools/testing/selftests/kvm/lib/x86/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86/processor.c
> @@ -694,6 +694,8 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id)
>  	vcpu_init_sregs(vm, vcpu);
>  	vcpu_init_xcrs(vm, vcpu);
>  
> +	vcpu->initial_stack_addr = stack_vaddr;
> +
>  	/* Setup guest general purpose registers */
>  	vcpu_regs_get(vcpu, &regs);
>  	regs.rflags = regs.rflags | 0x2;
> -- 
> 2.51.0.rc0.155.g4a0f42376b-goog
>