Re: [PATCH v3 4/4] x86/svm: Drop emulation of Intel's SYSENTER behaviour on AMD systems

[Jan Beulich <jbeulich@xxxxxxxx>]

On 13.02.2026 12:42, Alejandro Vallejo wrote:
> @@ -501,6 +492,9 @@ static void svm_save_cpu_state(struct vcpu *v, struct 
> hvm_hw_cpu *data)
>  {
>      struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;
>  
> +    data->sysenter_cs      = vmcb->sysenter_cs;
> +    data->sysenter_esp     = vmcb->sysenter_esp;
> +    data->sysenter_eip     = vmcb->sysenter_eip;
>      data->shadow_gs        = vmcb->kerngsbase;
>      data->msr_lstar        = vmcb->lstar;
>      data->msr_star         = vmcb->star;

May I suggest to do writes by increasing address order? I.e. while this
already looks fine, ...

> @@ -512,11 +506,14 @@ static void svm_load_cpu_state(struct vcpu *v, struct 
> hvm_hw_cpu *data)
>  {
>      struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;
>  
> -    vmcb->kerngsbase = data->shadow_gs;
> -    vmcb->lstar      = data->msr_lstar;
> -    vmcb->star       = data->msr_star;
> -    vmcb->cstar      = data->msr_cstar;
> -    vmcb->sfmask     = data->msr_syscall_mask;
> +    vmcb->sysenter_cs  = data->sysenter_cs;
> +    vmcb->sysenter_esp = data->sysenter_esp;
> +    vmcb->sysenter_eip = data->sysenter_eip;
> +    vmcb->kerngsbase   = data->shadow_gs;
> +    vmcb->lstar        = data->msr_lstar;
> +    vmcb->star         = data->msr_star;
> +    vmcb->cstar        = data->msr_cstar;
> +    vmcb->sfmask       = data->msr_syscall_mask;
>      v->arch.hvm.guest_efer = data->msr_efer;
>      svm_update_guest_efer(v);
>  }

... your additions would want to move down here (and the other writes may
then want re-ordering as well). Preferably with that:
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan