[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH v5 rebased 4/4] nested vmx: enable VMCS shadowing feature



On Wed, Jan 23, 2013 at 6:32 AM, Dongxiao Xu <dongxiao.xu@xxxxxxxxx> wrote:
>
> The current logic for handling the non-root VMREAD/VMWRITE is by
> VM-Exit and emulate, which may bring certain overhead.
>
> On new Intel platform, it introduces a new feature called VMCS
> shadowing, where non-root VMREAD/VMWRITE will not trigger VM-Exit,
> and the hardware will read/write the virtual VMCS instead.
> This is proved to have performance improvement with the feature.
>
> Signed-off-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
> ---
>  xen/arch/x86/hvm/vmx/vmcs.c        |    9 ++++
>  xen/arch/x86/hvm/vmx/vvmx.c        |   82
> ++++++++++++++++++++++++++++++++++++
>  xen/include/asm-x86/hvm/vmx/vmcs.h |   18 +++++++-
>  3 files changed, 108 insertions(+), 1 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
> index f89ea93..69b7dae 100644
> --- a/xen/arch/x86/hvm/vmx/vmcs.c
> +++ b/xen/arch/x86/hvm/vmx/vmcs.c
> @@ -92,6 +92,7 @@ static void __init vmx_display_features(void)
>      P(cpu_has_vmx_unrestricted_guest, "Unrestricted Guest");
>      P(cpu_has_vmx_apic_reg_virt, "APIC Register Virtualization");
>      P(cpu_has_vmx_virtual_intr_delivery, "Virtual Interrupt Delivery");
> +    P(cpu_has_vmx_vmcs_shadowing, "VMCS shadowing");
>  #undef P
>
>      if ( !printed )
> @@ -133,6 +134,7 @@ static int vmx_init_vmcs_config(void)
>      u32 _vmx_cpu_based_exec_control;
>      u32 _vmx_secondary_exec_control = 0;
>      u64 _vmx_ept_vpid_cap = 0;
> +    u64 _vmx_misc_cap = 0;
>      u32 _vmx_vmexit_control;
>      u32 _vmx_vmentry_control;
>      bool_t mismatch = 0;
> @@ -180,6 +182,9 @@ static int vmx_init_vmcs_config(void)
>                 SECONDARY_EXEC_ENABLE_RDTSCP |
>                 SECONDARY_EXEC_PAUSE_LOOP_EXITING |
>                 SECONDARY_EXEC_ENABLE_INVPCID);
> +        rdmsrl(MSR_IA32_VMX_MISC, _vmx_misc_cap);
> +        if ( _vmx_misc_cap & VMX_MISC_VMWRITE_ALL )
> +            opt |= SECONDARY_EXEC_ENABLE_VMCS_SHADOWING;
>          if ( opt_vpid_enabled )
>              opt |= SECONDARY_EXEC_ENABLE_VPID;
>          if ( opt_unrestricted_guest_enabled )
> @@ -383,6 +388,8 @@ static void __vmx_clear_vmcs(void *info)
>      if ( arch_vmx->active_cpu == smp_processor_id() )
>      {
>          __vmpclear(virt_to_maddr(arch_vmx->vmcs));
> +        if ( arch_vmx->vmcs_shadow_maddr )
> +            __vmpclear(arch_vmx->vmcs_shadow_maddr);
>
>          arch_vmx->active_cpu = -1;
>          arch_vmx->launched   = 0;
> @@ -720,6 +727,8 @@ void vmx_vmcs_switch(struct vmcs_struct *from, struct
> vmcs_struct *to)
>      spin_lock(&vmx->vmcs_lock);
>
>      __vmpclear(virt_to_maddr(from));
> +    if ( vmx->vmcs_shadow_maddr )
> +        __vmpclear(vmx->vmcs_shadow_maddr);
>      __vmptrld(virt_to_maddr(to));
>
>      vmx->vmcs = to;
> diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
> index 1e1ad56..3c152c5 100644
> --- a/xen/arch/x86/hvm/vmx/vvmx.c
> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
> @@ -64,6 +64,48 @@ int nvmx_vcpu_initialise(struct vcpu *v)
>          gdprintk(XENLOG_ERR, "nest: allocation for shadow vmcs
> failed\n");
>         goto out;
>      }
> +
> +    /* non-root VMREAD/VMWRITE bitmap. */
> +    if ( cpu_has_vmx_vmcs_shadowing )
> +    {
> +        struct page_info *vmread_bitmap, *vmwrite_bitmap;
> +        unsigned long *vr, *vw;
> +
> +        vmread_bitmap = alloc_domheap_page(NULL, 0);
> +        if ( !vmread_bitmap )
> +        {
> +            gdprintk(XENLOG_ERR, "nest: allocation for vmread bitmap
> failed\n");
> +            goto out1;
> +        }
> +        v->arch.hvm_vmx.vmread_bitmap = vmread_bitmap;
> +
> +        vmwrite_bitmap = alloc_domheap_page(NULL, 0);
> +        if ( !vmwrite_bitmap )
> +        {
> +            gdprintk(XENLOG_ERR, "nest: allocation for vmwrite bitmap
> failed\n");
> +            goto out2;
> +        }
> +        v->arch.hvm_vmx.vmwrite_bitmap = vmwrite_bitmap;
> +
> +        vr = __map_domain_page(vmread_bitmap);
> +        vw = __map_domain_page(vmwrite_bitmap);
> +
> +        clear_page(vr);
> +        clear_page(vw);
> +
> +        /*
> +         * For the following 4 encodings, we need to handle them in VMM.
> +         * Let them vmexit as usual.
> +         */
> +        set_bit(IO_BITMAP_A, vw);
> +        set_bit(IO_BITMAP_A_HIGH, vw);
> +        set_bit(IO_BITMAP_B, vw);
> +        set_bit(IO_BITMAP_B_HIGH, vw);
> +
> +        unmap_domain_page(vr);
> +        unmap_domain_page(vw);
> +    }
> +
>      nvmx->ept.enabled = 0;
>      nvmx->guest_vpid = 0;
>      nvmx->vmxon_region_pa = 0;
> @@ -76,6 +118,10 @@ int nvmx_vcpu_initialise(struct vcpu *v)
>      nvmx->msrbitmap = NULL;
>      INIT_LIST_HEAD(&nvmx->launched_list);
>      return 0;
> +out2:
> +    free_domheap_page(v->arch.hvm_vmx.vmread_bitmap);
> +out1:
> +    free_xenheap_page(nvcpu->nv_n2vmcx);
>  out:
>      return -ENOMEM;
>  }
> @@ -106,6 +152,11 @@ void nvmx_vcpu_destroy(struct vcpu *v)
>          list_del(&item->node);
>          xfree(item);
>      }
> +
> +    if ( v->arch.hvm_vmx.vmread_bitmap )
> +        free_domheap_page(v->arch.hvm_vmx.vmread_bitmap);
> +    if ( v->arch.hvm_vmx.vmwrite_bitmap )
> +        free_domheap_page(v->arch.hvm_vmx.vmwrite_bitmap);
>  }
>
>  void nvmx_domain_relinquish_resources(struct domain *d)
> @@ -1035,6 +1086,32 @@ static bool_t nvmx_vpid_enabled(struct nestedvcpu
> *nvcpu)
>      return 0;
>  }
>
> +static void nvmx_set_vmcs_pointer(struct vcpu *v, struct vmcs_struct
> *vvmcs)
> +{
> +    unsigned long vvmcs_mfn = domain_page_map_to_mfn(vvmcs);
> +    paddr_t vvmcs_maddr = vvmcs_mfn << PAGE_SHIFT;
> +
> +    __vmpclear(vvmcs_maddr);
> +    vvmcs->vmcs_revision_id |= VMCS_RID_TYPE_MASK;
> +    v->arch.hvm_vmx.vmcs_shadow_maddr = vvmcs_maddr;
> +    __vmwrite(VMCS_LINK_POINTER, vvmcs_maddr);
> +    __vmwrite(VMREAD_BITMAP,
> page_to_maddr(v->arch.hvm_vmx.vmread_bitmap));
> +    __vmwrite(VMWRITE_BITMAP,
> page_to_maddr(v->arch.hvm_vmx.vmwrite_bitmap));
> +}
> +
> +static void nvmx_clear_vmcs_pointer(struct vcpu *v, struct vmcs_struct
> *vvmcs)
> +{
> +    unsigned long vvmcs_mfn = domain_page_map_to_mfn(vvmcs);
> +    paddr_t vvmcs_maddr = vvmcs_mfn << PAGE_SHIFT;
> +
> +    __vmpclear(vvmcs_maddr);
> +    vvmcs->vmcs_revision_id &= ~VMCS_RID_TYPE_MASK;
> +    v->arch.hvm_vmx.vmcs_shadow_maddr = 0;
> +    __vmwrite(VMCS_LINK_POINTER, ~0ul);
> +    __vmwrite(VMREAD_BITMAP, 0);
> +    __vmwrite(VMWRITE_BITMAP, 0);
> +}
> +
>  static void virtual_vmentry(struct cpu_user_regs *regs)
>  {
>      struct vcpu *v = current;
> @@ -1476,6 +1553,9 @@ int nvmx_handle_vmptrld(struct cpu_user_regs *regs)
>          __map_msr_bitmap(v);
>      }
>
> +    if ( cpu_has_vmx_vmcs_shadowing )
> +        nvmx_set_vmcs_pointer(v, nvcpu->nv_vvmcx);
> +
>      vmreturn(regs, VMSUCCEED);
>
>  out:
> @@ -1526,6 +1606,8 @@ int nvmx_handle_vmclear(struct cpu_user_regs *regs)
>
>      if ( gpa == nvcpu->nv_vvmcxaddr )
>      {
> +        if ( cpu_has_vmx_vmcs_shadowing )
> +            nvmx_clear_vmcs_pointer(v, nvcpu->nv_vvmcx);
>          clear_vvmcs_launched(&nvmx->launched_list,
>              domain_page_map_to_mfn(nvcpu->nv_vvmcx));
>          nvmx_purge_vvmcs(v);
> diff --git a/xen/include/asm-x86/hvm/vmx/vmcs.h
> b/xen/include/asm-x86/hvm/vmx/vmcs.h
> index 652dc21..ba02221 100644
> --- a/xen/include/asm-x86/hvm/vmx/vmcs.h
> +++ b/xen/include/asm-x86/hvm/vmx/vmcs.h
> @@ -81,6 +81,8 @@ struct vmx_domain {
>  struct arch_vmx_struct {
>      /* Virtual address of VMCS. */
>      struct vmcs_struct  *vmcs;
> +    /* VMCS shadow machine address. */
> +    paddr_t             vmcs_shadow_maddr;
>
>      /* Protects remote usage of VMCS (VMPTRLD/VMCLEAR). */
>      spinlock_t           vmcs_lock;
> @@ -125,6 +127,10 @@ struct arch_vmx_struct {
>      /* Remember EFLAGS while in virtual 8086 mode */
>      uint32_t             vm86_saved_eflags;
>      int                  hostenv_migrated;
> +
> +    /* Bitmap to control vmexit policy for Non-root VMREAD/VMWRITE */
> +    struct page_info     *vmread_bitmap;
> +    struct page_info     *vmwrite_bitmap;
>  };
>
>  int vmx_create_vmcs(struct vcpu *v);
> @@ -191,6 +197,7 @@ extern u32 vmx_vmentry_control;
>  #define SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY    0x00000200
>  #define SECONDARY_EXEC_PAUSE_LOOP_EXITING       0x00000400
>  #define SECONDARY_EXEC_ENABLE_INVPCID           0x00001000
> +#define SECONDARY_EXEC_ENABLE_VMCS_SHADOWING    0x00004000
>  extern u32 vmx_secondary_exec_control;
>
>  extern bool_t cpu_has_vmx_ins_outs_instr_info;
> @@ -205,6 +212,8 @@ extern bool_t cpu_has_vmx_ins_outs_instr_info;
>  #define VMX_EPT_INVEPT_SINGLE_CONTEXT           0x02000000
>  #define VMX_EPT_INVEPT_ALL_CONTEXT              0x04000000
>
> +#define VMX_MISC_VMWRITE_ALL                    0x20000000
> +
>  #define VMX_VPID_INVVPID_INSTRUCTION
> 0x100000000ULL
>  #define VMX_VPID_INVVPID_INDIVIDUAL_ADDR
> 0x10000000000ULL
>  #define VMX_VPID_INVVPID_SINGLE_CONTEXT
> 0x20000000000ULL
> @@ -244,7 +253,10 @@ extern bool_t cpu_has_vmx_ins_outs_instr_info;
>      (vmx_secondary_exec_control & SECONDARY_EXEC_APIC_REGISTER_VIRT)
>  #define cpu_has_vmx_virtual_intr_delivery \
>      (vmx_secondary_exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY)
> -#define cpu_has_vmx_vmcs_shadowing 0
> +#define cpu_has_vmx_vmcs_shadowing \
> +    (vmx_secondary_exec_control & SECONDARY_EXEC_ENABLE_VMCS_SHADOWING)
> +
> +#define VMCS_RID_TYPE_MASK              0x80000000
>
>  /* GUEST_INTERRUPTIBILITY_INFO flags. */
>  #define VMX_INTR_SHADOW_STI             0x00000001
> @@ -305,6 +317,10 @@ enum vmcs_field {
>      EOI_EXIT_BITMAP2_HIGH           = 0x00002021,
>      EOI_EXIT_BITMAP3                = 0x00002022,
>      EOI_EXIT_BITMAP3_HIGH           = 0x00002023,
> +    VMREAD_BITMAP                   = 0x00002026,
> +    VMREAD_BITMAP_HIGH              = 0x00002027,
> +    VMWRITE_BITMAP                  = 0x00002028,
> +    VMWRITE_BITMAP_HIGH             = 0x00002029,
>      GUEST_PHYSICAL_ADDRESS          = 0x00002400,
>      GUEST_PHYSICAL_ADDRESS_HIGH     = 0x00002401,
>      VMCS_LINK_POINTER               = 0x00002800,
> --
> 1.7.1
>

Acked-by: Jun Nakajima <jun.nakajima@xxxxxxxxx>


--
Jun
Intel Open Source Technology Center

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.