Re: [RFC PATCH v5 03/29] KVM: selftests: Store initial stack address in struct kvm_vcpu

[Binbin Wu <binbin.wu@linux.intel.com>]

On 12/13/2023 4:46 AM, Sagi Shahar wrote:
> From: Ackerley Tng <ackerleytng@google.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.
>
> We 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.
>
> Signed-off-by: Ackerley Tng <ackerleytng@google.com>
> Signed-off-by: Ryan Afranji <afranji@google.com>
> Signed-off-by: Sagi Shahar <sagis@google.com>
> ---
>   tools/testing/selftests/kvm/include/kvm_util_base.h | 1 +
>   tools/testing/selftests/kvm/lib/x86_64/processor.c  | 4 +++-
>   2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
> index c2e5c5f25dfc..b353617fcdd1 100644
> --- a/tools/testing/selftests/kvm/include/kvm_util_base.h
> +++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
> @@ -68,6 +68,7 @@ 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_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> index f130f78a4974..b6b9438e0a33 100644
> --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
> +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
> @@ -621,10 +621,12 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id,
>   	vcpu_init_cpuid(vcpu, kvm_get_supported_cpuid());
>   	vcpu_setup(vm, vcpu);
>   
> +	vcpu->initial_stack_addr = stack_vaddr;
> +
>   	/* Setup guest general purpose registers */
>   	vcpu_regs_get(vcpu, &regs);
>   	regs.rflags = regs.rflags | 0x2;
> -	regs.rsp = stack_vaddr;
> +	regs.rsp = vcpu->initial_stack_addr;

Nit: No need to do this change.

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

>   	regs.rip = (unsigned long) guest_code;
>   	vcpu_regs_set(vcpu, &regs);
>