Re: [Xen-devel] [PATCH 1/2] xen: Drop XEN_DOMCTL_suppress_spurious_page_faults

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Tue, Aug 13, 2019 at 11:53:51AM +0100, Andrew Cooper wrote:
> This functionality is obsolete.  It was introduced by c/s 39407bed9c0 into
> Xend, but never exposed in libxl.
> 
> While not explicitly limited to PV guests, this is PV-only by virtue of its
> position in the pagefault handler.
> 
> Looking though the XenServer templates, this was used to work around bugs in
> the 32bit RHEL/CentOS 4.{5..7} kernels (fixed in 4.8).  RHEL 4 as a major
> version when out if support in 2017.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Python part:
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

Also, I confirm it isn't used in Qubes OS.

> ---
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Wei Liu <wl@xen.org>
> CC: Roger Pau Monné <roger.pau@citrix.com>
> CC: Ian Jackson <Ian.Jackson@citrix.com>
> CC: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
> CC: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> ---
>  tools/libxc/include/xenctrl.h       |  3 ---
>  tools/libxc/xc_domain.c             | 12 ------------
>  tools/python/xen/lowlevel/xc/xc.c   | 22 ----------------------
>  xen/arch/x86/domctl.c               |  4 ----
>  xen/arch/x86/traps.c                | 14 --------------
>  xen/include/asm-x86/domain.h        |  3 ---
>  xen/include/public/domctl.h         |  7 +------
>  xen/xsm/flask/hooks.c               |  1 -
>  xen/xsm/flask/policy/access_vectors |  3 +--
>  9 files changed, 2 insertions(+), 67 deletions(-)
> 
> diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
> index 0ff6ed9e70..a36896034a 100644
> --- a/tools/libxc/include/xenctrl.h
> +++ b/tools/libxc/include/xenctrl.h
> @@ -1787,9 +1787,6 @@ int xc_domain_set_machine_address_size(xc_interface *xch,
>  int xc_domain_get_machine_address_size(xc_interface *xch,
>  				       uint32_t domid);
>  
> -int xc_domain_suppress_spurious_page_faults(xc_interface *xch,
> -					  uint32_t domid);
> -
>  /* Set the target domain */
>  int xc_domain_set_target(xc_interface *xch,
>                           uint32_t domid,
> diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c
> index 05d771f2ce..64ca513aae 100644
> --- a/tools/libxc/xc_domain.c
> +++ b/tools/libxc/xc_domain.c
> @@ -2190,18 +2190,6 @@ int xc_domain_get_machine_address_size(xc_interface *xch, uint32_t domid)
>      return rc == 0 ? domctl.u.address_size.size : rc;
>  }
>  
> -int xc_domain_suppress_spurious_page_faults(xc_interface *xc, uint32_t domid)
> -{
> -    DECLARE_DOMCTL;
> -
> -    memset(&domctl, 0, sizeof(domctl));
> -    domctl.domain = domid;
> -    domctl.cmd    = XEN_DOMCTL_suppress_spurious_page_faults;
> -
> -    return do_domctl(xc, &domctl);
> -
> -}
> -
>  int xc_domain_debug_control(xc_interface *xc, uint32_t domid, uint32_t sop, uint32_t vcpu)
>  {
>      DECLARE_DOMCTL;
> diff --git a/tools/python/xen/lowlevel/xc/xc.c b/tools/python/xen/lowlevel/xc/xc.c
> index 188bfa34da..7e831a26a7 100644
> --- a/tools/python/xen/lowlevel/xc/xc.c
> +++ b/tools/python/xen/lowlevel/xc/xc.c
> @@ -786,22 +786,6 @@ static PyObject *pyxc_dom_set_machine_address_size(XcObject *self,
>      Py_INCREF(zero);
>      return zero;
>  }
> -
> -static PyObject *pyxc_dom_suppress_spurious_page_faults(XcObject *self,
> -						      PyObject *args,
> -						      PyObject *kwds)
> -{
> -    uint32_t dom;
> -
> -    if (!PyArg_ParseTuple(args, "i", &dom))
> -	return NULL;
> -
> -    if (xc_domain_suppress_spurious_page_faults(self->xc_handle, dom) != 0)
> -	return pyxc_error_to_exception(self->xc_handle);
> -
> -    Py_INCREF(zero);
> -    return zero;
> -}
>  #endif /* __i386__ || __x86_64__ */
>  
>  static PyObject *pyxc_gnttab_hvm_seed(XcObject *self,
> @@ -2436,12 +2420,6 @@ static PyMethodDef pyxc_methods[] = {
>        "Set maximum machine address size for this domain.\n"
>        " dom [int]: Identifier of domain.\n"
>        " width [int]: Maximum machine address width.\n" },
> -
> -    { "domain_suppress_spurious_page_faults",
> -      (PyCFunction)pyxc_dom_suppress_spurious_page_faults,
> -      METH_VARARGS, "\n"
> -      "Do not propagate spurious page faults to this guest.\n"
> -      " dom [int]: Identifier of domain.\n" },
>  #endif
>  
>      { "dom_set_memshr", 
> diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> index 2d45e5b8a8..34a6f88b8a 100644
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -988,10 +988,6 @@ long arch_do_domctl(
>          }
>          break;
>  
> -    case XEN_DOMCTL_suppress_spurious_page_faults:
> -        d->arch.suppress_spurious_page_faults = 1;
> -        break;
> -
>  #ifdef CONFIG_HVM
>      case XEN_DOMCTL_debug_op:
>      {
> diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
> index 23069e25ec..350903add5 100644
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -1452,20 +1452,6 @@ void do_page_fault(struct cpu_user_regs *regs)
>                error_code, _p(addr));
>      }
>  
> -    if ( unlikely(current->domain->arch.suppress_spurious_page_faults) )
> -    {
> -        pf_type = spurious_page_fault(addr, regs);
> -        if ( (pf_type == smep_fault) || (pf_type == smap_fault))
> -        {
> -            printk(XENLOG_G_ERR "%pv fatal SM%cP violation\n",
> -                   current, (pf_type == smep_fault) ? 'E' : 'A');
> -
> -            domain_crash(current->domain);
> -        }
> -        if ( pf_type != real_fault )
> -            return;
> -    }
> -
>      if ( unlikely(regs->error_code & PFEC_reserved_bit) )
>          reserved_bit_page_fault(addr, regs);
>  
> diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
> index 933b85901f..8523c3f5e0 100644
> --- a/xen/include/asm-x86/domain.h
> +++ b/xen/include/asm-x86/domain.h
> @@ -339,9 +339,6 @@ struct arch_domain
>      /* Is shared-info page in 32-bit format? */
>      bool_t has_32bit_shinfo;
>  
> -    /* Domain cannot handle spurious page faults? */
> -    bool_t suppress_spurious_page_faults;
> -
>      /* Is PHYSDEVOP_eoi to automatically unmask the event channel? */
>      bool_t auto_unmask;
>  
> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> index 19486d5e32..726ce675e8 100644
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -698,11 +698,6 @@ struct xen_domctl_subscribe {
>  /* XEN_DOMCTL_set_machine_address_size */
>  /* XEN_DOMCTL_get_machine_address_size */
>  
> -/*
> - * Do not inject spurious page faults into this domain.
> - */
> -/* XEN_DOMCTL_suppress_spurious_page_faults */
> -
>  /* XEN_DOMCTL_debug_op */
>  #define XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_OFF         0
>  #define XEN_DOMCTL_DEBUG_OP_SINGLE_STEP_ON          1
> @@ -1172,7 +1167,7 @@ struct xen_domctl {
>  #define XEN_DOMCTL_get_device_group              50
>  #define XEN_DOMCTL_set_machine_address_size      51
>  #define XEN_DOMCTL_get_machine_address_size      52
> -#define XEN_DOMCTL_suppress_spurious_page_faults 53
> +/* #define XEN_DOMCTL_suppress_spurious_page_faults 53 - Obsolete */
>  #define XEN_DOMCTL_debug_op                      54
>  #define XEN_DOMCTL_gethvmcontext_partial         55
>  #define XEN_DOMCTL_vm_event_op                   56
> diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
> index 791c1f66af..fd5ec992cf 100644
> --- a/xen/xsm/flask/hooks.c
> +++ b/xen/xsm/flask/hooks.c
> @@ -712,7 +712,6 @@ static int flask_domctl(struct domain *d, int cmd)
>  
>      case XEN_DOMCTL_subscribe:
>      case XEN_DOMCTL_disable_migrate:
> -    case XEN_DOMCTL_suppress_spurious_page_faults:
>          return current_has_perm(d, SECCLASS_DOMAIN, DOMAIN__SET_MISC_INFO);
>  
>      case XEN_DOMCTL_set_virq_handler:
> diff --git a/xen/xsm/flask/policy/access_vectors b/xen/xsm/flask/policy/access_vectors
> index 194d743a71..c9ebd0f37e 100644
> --- a/xen/xsm/flask/policy/access_vectors
> +++ b/xen/xsm/flask/policy/access_vectors
> @@ -176,8 +176,7 @@ class domain
>      getpodtarget
>  # XENMEM_set_pod_target
>      setpodtarget
> -# XEN_DOMCTL_subscribe, XEN_DOMCTL_disable_migrate,
> -# XEN_DOMCTL_suppress_spurious_page_faults
> +# XEN_DOMCTL_subscribe, XEN_DOMCTL_disable_migrate
>      set_misc_info
>  # XEN_DOMCTL_set_virq_handler
>      set_virq_handler

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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