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Re: [Xen-devel] [PATCH V6] x86/altp2m: Hypercall to set altp2m view visibility


  • To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
  • From: Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>
  • Date: Wed, 4 Mar 2020 13:57:31 +0000
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  • Cc: Kevin Tian <kevin.tian@xxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Jun Nakajima <jun.nakajima@xxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Ian Jackson <ian.jackson@xxxxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Wed, 04 Mar 2020 13:57:43 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Thread-index: AQHV8VaFWzT4PZYI70qii0UzQw6fbqg4dwKA
  • Thread-topic: [PATCH V6] x86/altp2m: Hypercall to set altp2m view visibility

Hi George,

This is a kind reminder if you can take a look at this patch when you 
have the time.

Thanks,
Alex

On 03.03.2020 14:23, Alexandru Stefan ISAILA wrote:
> At this moment a guest can call vmfunc to change the altp2m view. This
> should be limited in order to avoid any unwanted view switch.
> 
> The new xc_altp2m_set_visibility() solves this by making views invisible
> to vmfunc.
> This is done by having a separate arch.altp2m_working_eptp that is
> populated and made invalid in the same places as altp2m_eptp. This is
> written to EPTP_LIST_ADDR.
> The views are made in/visible by marking them with INVALID_MFN or
> copying them back from altp2m_eptp.
> To have consistency the visibility also applies to
> p2m_switch_domain_altp2m_by_id().
> 
> Note: If altp2m mode is set to mixed the guest is able to change the view
> visibility and then call vmfunc.
> 
> Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
> ---
> CC: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> CC: Wei Liu <wl@xxxxxxx>
> CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> CC: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> CC: Jan Beulich <jbeulich@xxxxxxxx>
> CC: Julien Grall <julien@xxxxxxx>
> CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> CC: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
> CC: Jun Nakajima <jun.nakajima@xxxxxxxxx>
> CC: Kevin Tian <kevin.tian@xxxxxxxxx>
> ---
> Changes since V5:
>       - Change idx type from uint16_t to unsigned int
>       - Add rc var and dropped the err return from p2m_get_suppress_ve().
> 
> Changes since V4:
>       - Move p2m specific things from hvm to p2m.c
>       - Add comment for altp2m_idx bounds check
>       - Add altp2m_list_lock/unlock().
> 
> Changes since V3:
>       - Change var name form altp2m_idx to idx to shorten line length
>       - Add bounds check for idx
>       - Update commit message
>       - Add comment in xenctrl.h.
> 
> Changes since V2:
>       - Drop hap_enabled() check
>       - Reduce the indentation depth in hvm.c
>       - Fix assignment indentation
>       - Drop pad2.
> 
> Changes since V1:
>       - Drop double view from title.
> ---
>   tools/libxc/include/xenctrl.h   |  7 +++++++
>   tools/libxc/xc_altp2m.c         | 24 +++++++++++++++++++++++
>   xen/arch/x86/hvm/hvm.c          | 14 ++++++++++++++
>   xen/arch/x86/hvm/vmx/vmx.c      |  2 +-
>   xen/arch/x86/mm/hap/hap.c       | 15 +++++++++++++++
>   xen/arch/x86/mm/p2m-ept.c       |  1 +
>   xen/arch/x86/mm/p2m.c           | 34 +++++++++++++++++++++++++++++++--
>   xen/include/asm-x86/domain.h    |  1 +
>   xen/include/asm-x86/p2m.h       |  4 ++++
>   xen/include/public/hvm/hvm_op.h |  9 +++++++++
>   10 files changed, 108 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
> index fc6e57a1a0..2e6e652678 100644
> --- a/tools/libxc/include/xenctrl.h
> +++ b/tools/libxc/include/xenctrl.h
> @@ -1943,6 +1943,13 @@ int xc_altp2m_change_gfn(xc_interface *handle, 
> uint32_t domid,
>                            xen_pfn_t new_gfn);
>   int xc_altp2m_get_vcpu_p2m_idx(xc_interface *handle, uint32_t domid,
>                                  uint32_t vcpuid, uint16_t *p2midx);
> +/*
> + * Set view visibility for xc_altp2m_switch_to_view and vmfunc.
> + * Note: If altp2m mode is set to mixed the guest is able to change the view
> + * visibility and then call vmfunc.
> + */
> +int xc_altp2m_set_visibility(xc_interface *handle, uint32_t domid,
> +                             uint16_t view_id, bool visible);
>   
>   /**
>    * Mem paging operations.
> diff --git a/tools/libxc/xc_altp2m.c b/tools/libxc/xc_altp2m.c
> index 46fb725806..6987c9541f 100644
> --- a/tools/libxc/xc_altp2m.c
> +++ b/tools/libxc/xc_altp2m.c
> @@ -410,3 +410,27 @@ int xc_altp2m_get_vcpu_p2m_idx(xc_interface *handle, 
> uint32_t domid,
>       xc_hypercall_buffer_free(handle, arg);
>       return rc;
>   }
> +
> +int xc_altp2m_set_visibility(xc_interface *handle, uint32_t domid,
> +                             uint16_t view_id, bool visible)
> +{
> +    int rc;
> +
> +    DECLARE_HYPERCALL_BUFFER(xen_hvm_altp2m_op_t, arg);
> +
> +    arg = xc_hypercall_buffer_alloc(handle, arg, sizeof(*arg));
> +    if ( arg == NULL )
> +        return -1;
> +
> +    arg->version = HVMOP_ALTP2M_INTERFACE_VERSION;
> +    arg->cmd = HVMOP_altp2m_set_visibility;
> +    arg->domain = domid;
> +    arg->u.set_visibility.altp2m_idx = view_id;
> +    arg->u.set_visibility.visible = visible;
> +
> +    rc = xencall2(handle->xcall, __HYPERVISOR_hvm_op, HVMOP_altp2m,
> +                  HYPERCALL_BUFFER_AS_ARG(arg));
> +
> +    xc_hypercall_buffer_free(handle, arg);
> +    return rc;
> +}
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index db5d7b4d30..7e631e30dd 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -4564,6 +4564,7 @@ static int do_altp2m_op(
>       case HVMOP_altp2m_get_mem_access:
>       case HVMOP_altp2m_change_gfn:
>       case HVMOP_altp2m_get_p2m_idx:
> +    case HVMOP_altp2m_set_visibility:
>           break;
>   
>       default:
> @@ -4841,6 +4842,19 @@ static int do_altp2m_op(
>           break;
>       }
>   
> +    case HVMOP_altp2m_set_visibility:
> +    {
> +        unsigned int idx = a.u.set_visibility.altp2m_idx;
> +
> +        if ( a.u.set_visibility.pad )
> +            rc = -EINVAL;
> +        else if ( !altp2m_active(d) )
> +            rc = -EOPNOTSUPP;
> +        else
> +            rc = p2m_set_altp2m_view_visibility(d, idx,
> +                                                a.u.set_visibility.visible);
> +    }
> +
>       default:
>           ASSERT_UNREACHABLE();
>       }
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index d265ed46ad..bb44ef39a1 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2140,7 +2140,7 @@ static void vmx_vcpu_update_vmfunc_ve(struct vcpu *v)
>       {
>           v->arch.hvm.vmx.secondary_exec_control |= mask;
>           __vmwrite(VM_FUNCTION_CONTROL, VMX_VMFUNC_EPTP_SWITCHING);
> -        __vmwrite(EPTP_LIST_ADDR, virt_to_maddr(d->arch.altp2m_eptp));
> +        __vmwrite(EPTP_LIST_ADDR, 
> virt_to_maddr(d->arch.altp2m_working_eptp));
>   
>           if ( cpu_has_vmx_virt_exceptions )
>           {
> diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
> index 3d93f3451c..5969ec8922 100644
> --- a/xen/arch/x86/mm/hap/hap.c
> +++ b/xen/arch/x86/mm/hap/hap.c
> @@ -488,8 +488,17 @@ int hap_enable(struct domain *d, u32 mode)
>               goto out;
>           }
>   
> +        if ( (d->arch.altp2m_working_eptp = alloc_xenheap_page()) == NULL )
> +        {
> +            rv = -ENOMEM;
> +            goto out;
> +        }
> +
>           for ( i = 0; i < MAX_EPTP; i++ )
> +        {
>               d->arch.altp2m_eptp[i] = mfn_x(INVALID_MFN);
> +            d->arch.altp2m_working_eptp[i] = mfn_x(INVALID_MFN);
> +        }
>   
>           for ( i = 0; i < MAX_ALTP2M; i++ )
>           {
> @@ -523,6 +532,12 @@ void hap_final_teardown(struct domain *d)
>               d->arch.altp2m_eptp = NULL;
>           }
>   
> +        if ( d->arch.altp2m_working_eptp )
> +        {
> +            free_xenheap_page(d->arch.altp2m_working_eptp);
> +            d->arch.altp2m_working_eptp = NULL;
> +        }
> +
>           for ( i = 0; i < MAX_ALTP2M; i++ )
>               p2m_teardown(d->arch.altp2m_p2m[i]);
>       }
> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
> index eb0f0edfef..6539ca619b 100644
> --- a/xen/arch/x86/mm/p2m-ept.c
> +++ b/xen/arch/x86/mm/p2m-ept.c
> @@ -1368,6 +1368,7 @@ void p2m_init_altp2m_ept(struct domain *d, unsigned int 
> i)
>       ept = &p2m->ept;
>       ept->mfn = pagetable_get_pfn(p2m_get_pagetable(p2m));
>       d->arch.altp2m_eptp[array_index_nospec(i, MAX_EPTP)] = ept->eptp;
> +    d->arch.altp2m_working_eptp[array_index_nospec(i, MAX_EPTP)] = ept->eptp;
>   }
>   
>   unsigned int p2m_find_altp2m_by_eptp(struct domain *d, uint64_t eptp)
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index 3719deae77..0677691783 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -2516,6 +2516,7 @@ void p2m_flush_altp2m(struct domain *d)
>       {
>           p2m_reset_altp2m(d, i, ALTP2M_DEACTIVATE);
>           d->arch.altp2m_eptp[i] = mfn_x(INVALID_MFN);
> +        d->arch.altp2m_working_eptp[i] = mfn_x(INVALID_MFN);
>       }
>   
>       altp2m_list_unlock(d);
> @@ -2635,7 +2636,9 @@ int p2m_destroy_altp2m_by_id(struct domain *d, unsigned 
> int idx)
>           {
>               p2m_reset_altp2m(d, idx, ALTP2M_DEACTIVATE);
>               d->arch.altp2m_eptp[array_index_nospec(idx, MAX_EPTP)] =
> -            mfn_x(INVALID_MFN);
> +                mfn_x(INVALID_MFN);
> +            d->arch.altp2m_working_eptp[array_index_nospec(idx, MAX_EPTP)] =
> +                mfn_x(INVALID_MFN);
>               rc = 0;
>           }
>       }
> @@ -2662,7 +2665,7 @@ int p2m_switch_domain_altp2m_by_id(struct domain *d, 
> unsigned int idx)
>       rc = -EINVAL;
>       altp2m_list_lock(d);
>   
> -    if ( d->arch.altp2m_eptp[idx] != mfn_x(INVALID_MFN) )
> +    if ( d->arch.altp2m_working_eptp[idx] != mfn_x(INVALID_MFN) )
>       {
>           for_each_vcpu( d, v )
>               if ( idx != vcpu_altp2m(v).p2midx )
> @@ -3146,6 +3149,33 @@ int p2m_get_suppress_ve(struct domain *d, gfn_t gfn, 
> bool *suppress_ve,
>   
>       return rc;
>   }
> +
> +int p2m_set_altp2m_view_visibility(struct domain *d, unsigned int altp2m_idx,
> +                                   uint8_t visible)
> +{
> +    int rc = 0;
> +
> +    altp2m_list_lock(d);
> +
> +    /*
> +     * Eptp index is correlated with altp2m index and should not exceed
> +     * min(MAX_ALTP2M, MAX_EPTP).
> +     */
> +    if ( altp2m_idx >= min(ARRAY_SIZE(d->arch.altp2m_p2m), MAX_EPTP) ||
> +         d->arch.altp2m_eptp[array_index_nospec(altp2m_idx, MAX_EPTP)] ==
> +         mfn_x(INVALID_MFN) )
> +        rc = -EINVAL;
> +    else if ( visible )
> +        d->arch.altp2m_working_eptp[array_index_nospec(altp2m_idx, 
> MAX_EPTP)] =
> +            d->arch.altp2m_eptp[array_index_nospec(altp2m_idx, MAX_EPTP)];
> +    else
> +        d->arch.altp2m_working_eptp[array_index_nospec(altp2m_idx, 
> MAX_EPTP)] =
> +            mfn_x(INVALID_MFN);
> +
> +    altp2m_list_unlock(d);
> +
> +    return rc;
> +}
>   #endif
>   
>   /*
> diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
> index 105adf96eb..800e12eae5 100644
> --- a/xen/include/asm-x86/domain.h
> +++ b/xen/include/asm-x86/domain.h
> @@ -327,6 +327,7 @@ struct arch_domain
>       struct p2m_domain *altp2m_p2m[MAX_ALTP2M];
>       mm_lock_t altp2m_list_lock;
>       uint64_t *altp2m_eptp;
> +    uint64_t *altp2m_working_eptp;
>   #endif
>   
>       /* NB. protected by d->event_lock and by irq_desc[irq].lock */
> diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
> index 0cf531abb7..0f7ec4a9f6 100644
> --- a/xen/include/asm-x86/p2m.h
> +++ b/xen/include/asm-x86/p2m.h
> @@ -897,6 +897,10 @@ int p2m_change_altp2m_gfn(struct domain *d, unsigned int 
> idx,
>   int p2m_altp2m_propagate_change(struct domain *d, gfn_t gfn,
>                                   mfn_t mfn, unsigned int page_order,
>                                   p2m_type_t p2mt, p2m_access_t p2ma);
> +
> +/* Set a specific p2m view visibility */
> +int p2m_set_altp2m_view_visibility(struct domain *d, unsigned int idx,
> +                                   uint8_t visible);
>   #else
>   struct p2m_domain *p2m_get_altp2m(struct vcpu *v);
>   static inline void p2m_altp2m_check(struct vcpu *v, uint16_t idx) {}
> diff --git a/xen/include/public/hvm/hvm_op.h b/xen/include/public/hvm/hvm_op.h
> index b599d3cbd0..870ec52060 100644
> --- a/xen/include/public/hvm/hvm_op.h
> +++ b/xen/include/public/hvm/hvm_op.h
> @@ -318,6 +318,12 @@ struct xen_hvm_altp2m_get_vcpu_p2m_idx {
>       uint16_t altp2m_idx;
>   };
>   
> +struct xen_hvm_altp2m_set_visibility {
> +    uint16_t altp2m_idx;
> +    uint8_t visible;
> +    uint8_t pad;
> +};
> +
>   struct xen_hvm_altp2m_op {
>       uint32_t version;   /* HVMOP_ALTP2M_INTERFACE_VERSION */
>       uint32_t cmd;
> @@ -350,6 +356,8 @@ struct xen_hvm_altp2m_op {
>   #define HVMOP_altp2m_get_p2m_idx          14
>   /* Set the "Supress #VE" bit for a range of pages */
>   #define HVMOP_altp2m_set_suppress_ve_multi 15
> +/* Set visibility for a given altp2m view */
> +#define HVMOP_altp2m_set_visibility       16
>       domid_t domain;
>       uint16_t pad1;
>       uint32_t pad2;
> @@ -367,6 +375,7 @@ struct xen_hvm_altp2m_op {
>           struct xen_hvm_altp2m_suppress_ve_multi    suppress_ve_multi;
>           struct xen_hvm_altp2m_vcpu_disable_notify  disable_notify;
>           struct xen_hvm_altp2m_get_vcpu_p2m_idx     get_vcpu_p2m_idx;
> +        struct xen_hvm_altp2m_set_visibility       set_visibility;
>           uint8_t pad[64];
>       } u;
>   };
> 
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