Re: [Xen-devel] [PATCH V3 3/6] x86/xsaves: enable xsaves/xrstors for hvm guest

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 05/08/15 02:57, Shuai Ruan wrote:
> This patch enables xsaves for hvm guest, includes:
> 1.handle xsaves vmcs init and vmexit.
> 2.add logic to write/read the XSS msr.
>
> Signed-off-by: Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>
> ---
>  xen/arch/x86/hvm/hvm.c             | 44 
> ++++++++++++++++++++++++++++++++++++++
>  xen/arch/x86/hvm/vmx/vmcs.c        |  7 +++++-
>  xen/arch/x86/hvm/vmx/vmx.c         | 18 ++++++++++++++++
>  xen/arch/x86/xstate.c              |  4 ++--
>  xen/include/asm-x86/hvm/vmx/vmcs.h |  5 +++++
>  xen/include/asm-x86/hvm/vmx/vmx.h  |  2 ++
>  xen/include/asm-x86/xstate.h       |  2 +-
>  7 files changed, 78 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index c07e3ef..e5cf761 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -4370,6 +4370,10 @@ void hvm_hypervisor_cpuid_leaf(uint32_t sub_idx,
>      }
>  }
>  
> +#define XSAVEOPT     (1 << 0)
> +#define XSAVEC               (1 << 1)
> +#define XGETBV1      (1 << 2)
> +#define XSAVES               (1 << 3)

These should be in cpufeature.h, not here.

>  void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx,
>                                     unsigned int *ecx, unsigned int *edx)
>  {
> @@ -4456,6 +4460,34 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, 
> unsigned int *ebx,
>                      *ebx = _eax + _ebx;
>              }
>          }
> +        if ( count == 1 )
> +        {
> +            if ( cpu_has_xsaves )
> +            {
> +                *ebx = XSTATE_AREA_MIN_SIZE;
> +                if ( v->arch.xcr0 | v->arch.msr_ia32_xss )
> +                    for ( sub_leaf = 2; sub_leaf < 63; sub_leaf++ )
> +                    {
> +                        if ( !((v->arch.xcr0 | v->arch.msr_ia32_xss)
> +                        & (1ULL << sub_leaf)) )
> +                            continue;
> +                        domain_cpuid(d, input, sub_leaf, &_eax, &_ebx, &_ecx,
> +                                     &_edx);
> +                        *ebx =  *ebx + _eax;
> +                    }
> +            }
> +            else
> +            {
> +                *eax &= ~XSAVES;
> +                *ebx = *ecx = *edx = 0;
> +            }
> +            if ( !cpu_has_xgetbv1 )
> +                *eax &= ~XGETBV1;
> +            if ( !cpu_has_xsavec )
> +                *eax &= ~XSAVEC;
> +            if ( !cpu_has_xsaveopt )
> +                *eax &= ~XSAVEOPT;
> +        }

Urgh - I really need to get domain cpuid fixed in Xen.  This is
currently making a very bad situation a little worse.

>          break;
>  
>      case 0x80000001:
> @@ -4555,6 +4587,12 @@ int hvm_msr_read_intercept(unsigned int msr, uint64_t 
> *msr_content)
>          *msr_content = v->arch.hvm_vcpu.guest_efer;
>          break;
>  
> +    case MSR_IA32_XSS:
> +        if ( !cpu_has_vmx_xsaves )

vmx_xsaves has nothing to do with this here.  I presume you mean
cpu_has_xsave?

> +            goto gp_fault;
> +        *msr_content = v->arch.msr_ia32_xss;
> +        break;
> +
>      case MSR_IA32_TSC:
>          *msr_content = _hvm_rdtsc_intercept();
>          break;
> @@ -4687,6 +4725,12 @@ int hvm_msr_write_intercept(unsigned int msr, uint64_t 
> msr_content,
>             return X86EMUL_EXCEPTION;
>          break;
>  
> +    case MSR_IA32_XSS:
> +        if ( !cpu_has_vmx_xsaves )
> +            goto gp_fault;
> +        v->arch.msr_ia32_xss = msr_content;

You must validate msr_content here and possibly hand a gp fault back to
the guest.

> +        break;
> +
>      case MSR_IA32_TSC:
>          hvm_set_guest_tsc(v, msr_content);
>          break;
> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
> index 4c5ceb5..8e61e3f 100644
> --- a/xen/arch/x86/hvm/vmx/vmcs.c
> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> @@ -230,7 +230,8 @@ static int vmx_init_vmcs_config(void)
>                 SECONDARY_EXEC_ENABLE_EPT |
>                 SECONDARY_EXEC_ENABLE_RDTSCP |
>                 SECONDARY_EXEC_PAUSE_LOOP_EXITING |
> -               SECONDARY_EXEC_ENABLE_INVPCID);
> +               SECONDARY_EXEC_ENABLE_INVPCID |
> +               SECONDARY_EXEC_XSAVES);
>          rdmsrl(MSR_IA32_VMX_MISC, _vmx_misc_cap);
>          if ( _vmx_misc_cap & VMX_MISC_VMWRITE_ALL )
>              opt |= SECONDARY_EXEC_ENABLE_VMCS_SHADOWING;
> @@ -921,6 +922,7 @@ void virtual_vmcs_vmwrite(void *vvmcs, u32 vmcs_encoding, 
> u64 val)
>      virtual_vmcs_exit(vvmcs);
>  }
>  
> +#define VMX_XSS_EXIT_BITMAP 0

This define definitely doesn't live here.

>  static int construct_vmcs(struct vcpu *v)
>  {
>      struct domain *d = v->domain;
> @@ -1204,6 +1206,9 @@ static int construct_vmcs(struct vcpu *v)
>          __vmwrite(GUEST_PAT, guest_pat);
>      }
>  
> +    if ( cpu_has_vmx_xsaves )
> +        __vmwrite(XSS_EXIT_BITMAP, VMX_XSS_EXIT_BITMAP);
> +
>      vmx_vmcs_exit(v);
>  
>      /* PVH: paging mode is updated by arch_set_info_guest(). */
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index d3183a8..64ff63b 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2708,6 +2708,16 @@ static int vmx_handle_apic_write(void)
>      return vlapic_apicv_write(current, exit_qualification & 0xfff);
>  }
>  
> +static void vmx_handle_xsaves(void)
> +{
> +    WARN();
> +}
> +
> +static void vmx_handle_xrstors(void)
> +{
> +    WARN();
> +}
> +

What is these supposed to do?  They are not an appropriate handlers.

~Andrew

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