Re: [Xen-devel] [PATCH] [v2] xen: Add FS and GS base to HVM VCPU context

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 24/04/2012 20:35, "Aravindh Puthiyaparambil" <aravindh@xxxxxxxxxxxx>
wrote:

> On Tue, Apr 24, 2012 at 10:33 AM, Aravindh Puthiyaparambil
> <aravindh@xxxxxxxxxxxx> wrote:
>> On Tue, Apr 24, 2012 at 12:52 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:

>>> Which still leaves one of gs_base_* unfilled in all cases. You'll need
>>> to get ahold of vmcb->kerngsbase (AMD/SVM) or
>>> v->arch.hvm_vmx.shadow_gs (Intel/VMX). You could either
>>> introduce a new wrapper, or expose {svm,vmx}_save_cpu_state()
>>> as a new function table entry, or pay the price of calling
>>> ->save_cpu_ctxt(). But you will need to pay extra attention to
>>> the case of the subject vCPU being current.
>> 
>> OK, I will try introducing a new wrapper that will return
>> vmcb->kerngsbase /  v->arch.hvm_vmx.shadow_gs.
> 
> Jan,
> 
> How does this look?

Only the code in domctl.c needs to be ifdef x86_64. In fact as it is, the
patch won't compile on i386, as you have inconsistently ifdef'ed. Just
remove the ifdefs as far as possible, we'd rather have dead code on i386
than ifdefs.

 -- Keir

> PS: Come submission time, I will send it out as two separate patches.
> 
> diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -1585,18 +1585,33 @@ void arch_get_info_guest(struct vcpu *v,
>          hvm_get_segment_register(v, x86_seg_ss, &sreg);
>          c.nat->user_regs.ss = sreg.sel;
>          hvm_get_segment_register(v, x86_seg_ds, &sreg);
>          c.nat->user_regs.ds = sreg.sel;
>          hvm_get_segment_register(v, x86_seg_es, &sreg);
>          c.nat->user_regs.es = sreg.sel;
>          hvm_get_segment_register(v, x86_seg_fs, &sreg);
>          c.nat->user_regs.fs = sreg.sel;
> +#ifdef __x86_64__
> +        c.nat->fs_base = sreg.base;
> +#endif
>          hvm_get_segment_register(v, x86_seg_gs, &sreg);
>          c.nat->user_regs.gs = sreg.sel;
> +#ifdef __x86_64__
> +        if ( ring_0(&c.nat->user_regs) )
> +        {
> +            c.nat->gs_base_kernel = sreg.base;
> +            c.nat->gs_base_user = hvm_get_shadow_gs_base(v);
> +        }
> +        else
> +        {
> +            c.nat->gs_base_user = sreg.base;
> +            c.nat->gs_base_kernel = hvm_get_shadow_gs_base(v);
> +        }
> +#endif
>      }
>      else
>      {
>          c(ldt_base = v->arch.pv_vcpu.ldt_base);
>          c(ldt_ents = v->arch.pv_vcpu.ldt_ents);
>          for ( i = 0; i < ARRAY_SIZE(v->arch.pv_vcpu.gdt_frames); ++i )
>              c(gdt_frames[i] = v->arch.pv_vcpu.gdt_frames[i]);
>  #ifdef CONFIG_COMPAT
> diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -640,16 +640,25 @@ static void svm_set_segment_register(str
>      default:
>          BUG();
>      }
> 
>      if ( sync )
>          svm_vmload(vmcb);
>  }
> 
> +#ifdef __x86_64__
> +static unsigned long svm_get_shadow_gs_base(struct vcpu *v)
> +{
> +    struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
> +
> +    return vmcb->kerngsbase;
> +}
> +#endif
> +
>  static int svm_set_guest_pat(struct vcpu *v, u64 gpat)
>  {
>      struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
> 
>      if ( !paging_mode_hap(v->domain) )
>          return 0;
> 
>      vmcb_set_g_pat(vmcb, gpat);
> @@ -1978,16 +1987,17 @@ static struct hvm_function_table __read_
>      .vcpu_destroy         = svm_vcpu_destroy,
>      .save_cpu_ctxt        = svm_save_vmcb_ctxt,
>      .load_cpu_ctxt        = svm_load_vmcb_ctxt,
>      .get_interrupt_shadow = svm_get_interrupt_shadow,
>      .set_interrupt_shadow = svm_set_interrupt_shadow,
>      .guest_x86_mode       = svm_guest_x86_mode,
>      .get_segment_register = svm_get_segment_register,
>      .set_segment_register = svm_set_segment_register,
> +    .get_shadow_gs_base   = svm_get_shadow_gs_base,
>      .update_host_cr3      = svm_update_host_cr3,
>      .update_guest_cr      = svm_update_guest_cr,
>      .update_guest_efer    = svm_update_guest_efer,
>      .set_guest_pat        = svm_set_guest_pat,
>      .get_guest_pat        = svm_get_guest_pat,
>      .set_tsc_offset       = svm_set_tsc_offset,
>      .inject_exception     = svm_inject_exception,
>      .init_hypercall_page  = svm_init_hypercall_page,
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -937,16 +937,23 @@ static void vmx_set_segment_register(str
>          break;
>      default:
>          BUG();
>      }
> 
>      vmx_vmcs_exit(v);
>  }
> 
> +#ifdef __x86_64__
> +static unsigned long vmx_get_shadow_gs_base(struct vcpu *v)
> +{
> +    return v->arch.hvm_vmx.shadow_gs;
> +}
> +#endif
> +
>  static int vmx_set_guest_pat(struct vcpu *v, u64 gpat)
>  {
>      if ( !cpu_has_vmx_pat || !paging_mode_hap(v->domain) )
>          return 0;
> 
>      vmx_vmcs_enter(v);
>      __vmwrite(GUEST_PAT, gpat);
>  #ifdef __i386__
> @@ -1517,16 +1524,17 @@ static struct hvm_function_table __read_
>      .vcpu_destroy         = vmx_vcpu_destroy,
>      .save_cpu_ctxt        = vmx_save_vmcs_ctxt,
>      .load_cpu_ctxt        = vmx_load_vmcs_ctxt,
>      .get_interrupt_shadow = vmx_get_interrupt_shadow,
>      .set_interrupt_shadow = vmx_set_interrupt_shadow,
>      .guest_x86_mode       = vmx_guest_x86_mode,
>      .get_segment_register = vmx_get_segment_register,
>      .set_segment_register = vmx_set_segment_register,
> +    .get_shadow_gs_base   = vmx_get_shadow_gs_base,
>      .update_host_cr3      = vmx_update_host_cr3,
>      .update_guest_cr      = vmx_update_guest_cr,
>      .update_guest_efer    = vmx_update_guest_efer,
>      .set_guest_pat        = vmx_set_guest_pat,
>      .get_guest_pat        = vmx_get_guest_pat,
>      .set_tsc_offset       = vmx_set_tsc_offset,
>      .inject_exception     = vmx_inject_exception,
>      .init_hypercall_page  = vmx_init_hypercall_page,
> diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
> --- a/xen/include/asm-x86/hvm/hvm.h
> +++ b/xen/include/asm-x86/hvm/hvm.h
> @@ -101,16 +101,19 @@ struct hvm_function_table {
>      /* Examine specifics of the guest state. */
>      unsigned int (*get_interrupt_shadow)(struct vcpu *v);
>      void (*set_interrupt_shadow)(struct vcpu *v, unsigned int intr_shadow);
>      int (*guest_x86_mode)(struct vcpu *v);
>      void (*get_segment_register)(struct vcpu *v, enum x86_segment seg,
>                                   struct segment_register *reg);
>      void (*set_segment_register)(struct vcpu *v, enum x86_segment seg,
>                                   struct segment_register *reg);
> +#ifdef __x86_64__
> +    unsigned long (*get_shadow_gs_base)(struct vcpu *v);
> +#endif
> 
>      /*
>       * Re-set the value of CR3 that Xen runs on when handling VM exits.
>       */
>      void (*update_host_cr3)(struct vcpu *v);
> 
>      /*
>       * Called to inform HVM layer that a guest CRn or EFER has changed.
> @@ -300,16 +303,23 @@ hvm_get_segment_register(struct vcpu *v,
> 
>  static inline void
>  hvm_set_segment_register(struct vcpu *v, enum x86_segment seg,
>                           struct segment_register *reg)
>  {
>      hvm_funcs.set_segment_register(v, seg, reg);
>  }
> 
> +#ifdef __x86_64__
> +static inline unsigned long hvm_get_shadow_gs_base(struct vcpu *v)
> +{
> +    return hvm_funcs.get_shadow_gs_base(v);
> +}
> +#endif
> +
>  #define is_viridian_domain(_d)                                             \
>   (is_hvm_domain(_d) && ((_d)->arch.hvm_domain.params[HVM_PARAM_VIRIDIAN]))
> 
>  void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx,
>                                     unsigned int *ecx, unsigned int *edx);
>  void hvm_migrate_timers(struct vcpu *v);
>  void hvm_do_resume(struct vcpu *v);
>  void hvm_migrate_pirqs(struct vcpu *v);
> 
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