> -----Original Message-----
> From: Jan Beulich [mailto:[email protected]]
> Sent: 16 October 2017 14:53
> To: Paul Durrant <[email protected]>
> Cc: Andrew Cooper <[email protected]>; Wei Liu
> <[email protected]>; George Dunlap <[email protected]>; Ian
> Jackson <[email protected]>; Stefano Stabellini
> <[email protected]>; [email protected]; Konrad Rzeszutek
> Wilk <[email protected]>; Tim (Xen.org) <[email protected]>
> Subject: Re: [PATCH v11 05/11] x86/mm: add HYPERVISOR_memory_op to
> acquire guest resources
>
> >>> On 12.10.17 at 18:25, <[email protected]> wrote:
> > @@ -402,14 +469,56 @@ int compat_memory_op(unsigned int cmd,
> XEN_GUEST_HANDLE_PARAM(void) compat)
> > rc = do_memory_op(cmd, nat.hnd);
> > if ( rc < 0 )
> > {
> > - if ( rc == -ENOBUFS && op == XENMEM_get_vnumainfo )
> > + switch ( op)
>
> Missing blank.
Oh yes.
>
> > {
> > - cmp.vnuma.nr_vnodes = nat.vnuma->nr_vnodes;
> > - cmp.vnuma.nr_vcpus = nat.vnuma->nr_vcpus;
> > - cmp.vnuma.nr_vmemranges = nat.vnuma->nr_vmemranges;
> > - if ( __copy_to_guest(compat, &cmp.vnuma, 1) )
> > - rc = -EFAULT;
> > + case XENMEM_get_vnumainfo:
> > + if ( rc == -ENOBUFS )
> > + {
> > + cmp.vnuma.nr_vnodes = nat.vnuma->nr_vnodes;
> > + cmp.vnuma.nr_vcpus = nat.vnuma->nr_vcpus;
> > + cmp.vnuma.nr_vmemranges = nat.vnuma->nr_vmemranges;
> > + if ( __copy_to_guest(compat, &cmp.vnuma, 1) )
> > + rc = -EFAULT;
> > + }
> > +
> > + break;
> > +
> > + case XENMEM_acquire_resource:
> > + {
> > + xen_ulong_t *xen_frame_list = (xen_ulong_t *)(nat.mar + 1);
>
> const
Ok.
>
> > + if ( rc == -EINVAL && xen_frame_list[0] != 0 )
>
> I think this will go wrong if you get -EINVAL for other than the
> specific reason you consider here, in particular when caller
> passed in a valid array. You'd need to also check for
> cmp.mar.nr_frames being zero. But see also below.
>
> > + {
> > + /*
> > + * The value of nr_frames passed to the implementation
> > + * was not the value passed by the caller, it was
> > + * overridden.
> > + * The value in xen_frame_list[0] is the maximum
> > + * number of frames that can be bounced so we need
> > + * to set cmp.nr_frames to the minimum of this and
> > + * the maximum number of frames allowed by the
> > + * implementation before passing back to the caller.
> > + */
> > + cmp.mar.nr_frames = min_t(unsigned int,
> > + xen_frame_list[0],
> > + nat.mar->nr_frames);
> > + rc = -E2BIG;
> > + }
> > +
> > + /* In either of these cases nr_frames is an OUT value */
> > + if ( rc == -EINVAL || rc == -E2BIG )
> > + {
> > + if ( copy_to_guest(compat, &cmp.mar, 1) )
> > + rc = -EFAULT;
>
> The two if()s should be combined. Also - __copy_field_to_guest()?
Yes, maybe that would neater.
>
> > + }
> > +
> > + break;
> > + }
> > + default:
> > + break;
>
> No real need for a default label. Yet if you want to keep it, please
> have a blank line ahead of it.
>
Ok.
> > @@ -535,6 +644,30 @@ int compat_memory_op(unsigned int cmd,
> XEN_GUEST_HANDLE_PARAM(void) compat)
> > rc = -EFAULT;
> > break;
> >
> > + case XENMEM_acquire_resource:
> > + {
> > + xen_ulong_t *xen_frame_list = (xen_ulong_t *)(nat.mar + 1);
>
> const
Ok.
>
> > + compat_ulong_t *compat_frame_list =
> > + (compat_ulong_t *)(nat.mar + 1);
> > +
> > + /* NOTE: the compat array overwrites the native array */
>
> Perhaps "the smaller compat array ..."?
Ok.
>
> > + for ( i = 0; i < cmp.mar.nr_frames; i++ )
> > + {
> > + compat_ulong_t frame = xen_frame_list[i];
> > +
> > + if ( frame != xen_frame_list[i] )
> > + return -ERANGE;
> > +
> > + compat_frame_list[i] = frame;
> > + }
> > +
> > + if ( __copy_to_compat_offset(cmp.mar.frame_list, 0,
> > + compat_frame_list,
> > + cmp.mar.nr_frames) )
> > + return -EFAULT;
> > +
> > + break;
> > + }
> > default:
>
> Again missing a blank line above here.
Ok.
>
> > --- a/xen/common/memory.c
> > +++ b/xen/common/memory.c
> > @@ -965,6 +965,88 @@ static long xatp_permission_check(struct domain
> *d, unsigned int space)
> > return xsm_add_to_physmap(XSM_TARGET, current->domain, d);
> > }
> >
> > +static int acquire_resource(XEN_GUEST_HANDLE_PARAM(void) arg)
> > +{
> > + struct domain *d, *currd = current->domain;
> > + xen_mem_acquire_resource_t xmar;
> > + unsigned long mfn_list[2];
> > + int rc;
> > +
> > + if ( copy_from_guest(&xmar, arg, 1) )
> > + return -EFAULT;
> > +
> > + if ( xmar.pad != 0 )
> > + return -EINVAL;
> > +
> > + if ( xmar.nr_frames == 0 ||
> > + xmar.nr_frames > ARRAY_SIZE(mfn_list) )
> > + {
> > + rc = xmar.nr_frames == 0 ? -EINVAL : -E2BIG;
>
> Querying the implementation limit should be possible without
> receiving an error. Hence my original suggestion to key this
> off of the handle being a null one (in which case non-zero
> nr_frames would indeed be -EINVAL), which afaics would also
> simplify some of the compat handling.
Ok, FAOD, do you mean that passing in nr_frames and a NULL handle should not
yield an error but should pass back the implementation limit of nr_frames?
>
> > + xmar.nr_frames = ARRAY_SIZE(mfn_list);
> > +
> > + if ( copy_to_guest(arg, &xmar, 1) )
> > + return -EFAULT;
> > +
> > + return rc;
> > + }
> > +
> > + d = rcu_lock_domain_by_any_id(xmar.domid);
> > + if ( d == NULL )
> > + return -ESRCH;
> > +
> > + rc = xsm_domain_resource_map(XSM_DM_PRIV, d);
> > + if ( rc )
> > + goto out;
> > +
> > + switch ( xmar.type )
> > + {
> > + default:
> > + rc = -EOPNOTSUPP;
> > + break;
> > + }
> > +
> > + if ( rc )
> > + goto out;
> > +
> > + if ( !paging_mode_translate(currd) )
> > + {
> > + if ( copy_to_guest(xmar.frame_list, mfn_list, xmar.nr_frames) )
> > + rc = -EFAULT;
> > + }
> > + else
> > + {
> > + xen_pfn_t gfn_list[ARRAY_SIZE(mfn_list)];
> > + unsigned int i;
> > +
> > + rc = -EFAULT;
> > + if ( copy_from_guest(gfn_list, xmar.frame_list,
> > + ARRAY_SIZE(gfn_list)) )
>
> You shouldn't copy more than xmar.nr_frames here, or else you
> risk running past a page boundary and perhaps into a non-
> present page.
Good point. That's clearly wrong.
> You consume ...
>
> > + goto out;
> > +
> > + for ( i = 0; i < xmar.nr_frames; i++ )
>
> ... exactly this many frames anyway.
>
> > + {
> > + rc = set_foreign_p2m_entry(currd, gfn_list[i],
> > + _mfn(mfn_list[i]));
> > + if ( rc )
> > + {
> > + while ( i-- != 0 )
> > + {
> > + int ignore;
> > +
> > + ignore = guest_physmap_remove_page(
> > + currd, _gfn(gfn_list[i]), _mfn(mfn_list[i]), 0);
>
> Why would an error here be plain ignored?
>
What could I usefully do with it? Should I just crash the domain at this point,
since I can't restore a consistent state?
> > @@ -1406,6 +1488,14 @@ long do_memory_op(unsigned long cmd,
> XEN_GUEST_HANDLE_PARAM(void) arg)
> > }
> > #endif
> >
> > + case XENMEM_acquire_resource:
> > +#ifdef CONFIG_X86
> > + rc = acquire_resource(arg);
> > +#else
> > + rc = -EOPNOTSUPP;
> > +#endif
>
> I think this will cause an "unused static function" warning on ARM.
...which is why I originally had the function wrapped in the #ifdef as well.
What do you want me to do?
>
> > --- a/xen/include/public/memory.h
> > +++ b/xen/include/public/memory.h
> > @@ -599,6 +599,47 @@ struct xen_reserved_device_memory_map {
> > typedef struct xen_reserved_device_memory_map
> xen_reserved_device_memory_map_t;
> > DEFINE_XEN_GUEST_HANDLE(xen_reserved_device_memory_map_t);
> >
> > +/*
> > + * Get the pages for a particular guest resource, so that they can be
> > + * mapped directly by a tools domain.
> > + */
> > +#define XENMEM_acquire_resource 28
> > +struct xen_mem_acquire_resource {
> > + /* IN - the domain whose resource is to be mapped */
> > + domid_t domid;
> > + /* IN - the type of resource */
> > + uint16_t type;
> > + /*
> > + * IN - a type-specific resource identifier, which must be zero
> > + * unless stated otherwise.
> > + */
> > + uint32_t id;
> > + /* IN/OUT - As an IN parameter number of (4K) frames of the resource
>
> Please don't say 4k here - this not being an x86-specific interface
> other system page sizes ought to be permitted.
I was under the impression that resources such as grant tables were only every
mapped in 4k chunks. Perhaps the 4k should type-specific? It needs to be
specified somewhere.
>
> > + * to be mapped. However, if the specified value is 0 then
> > + * -EINVAL will be returned and this field will be set to the
> > + * maximum value supported by the implementation. Also,
> > + * if the specified value exceeds the implementaton limit
> > + * then -E2BIG will be returned and, similarly, this field
> > + * will be set the maximum value supported by the
> > + * implementation.
> > + */
> > + uint32_t nr_frames;
> > + uint32_t pad;
> > + /* IN - the index of the initial frame to be mapped. This parameter
> > + * is optional if nr_frames is 0.
> > + */
> > + uint64_aligned_t frame;
> > + /* IN/OUT - If the tools domain is PV then, upon return, frame_list
> > + * will be populated with the MFNs of the resource.
> > + * If the tools domain is HVM then it is expected that, on
> > + * entry, frame_list will be populated with a list of GFNs
> > + * that will be mapped to the MFNs of the resource.
> > + * This parameter is optional if nr_frames is 0.
> > + */
>
> For both of these comments - s/optional/ignored/? And this, afaics,
> also applies to domid, type, and id, so perhaps better state once
> in the comment to (currently) nr_frames that all other fields except
> for pad will be ignored.
No, I think it's reasonable for domid, type and id to always be valid even if
nr_frames is zero.
>
> > --- a/xen/include/xsm/dummy.h
> > +++ b/xen/include/xsm/dummy.h
> > @@ -724,3 +724,9 @@ static XSM_INLINE int xsm_xen_version
> (XSM_DEFAULT_ARG uint32_t op)
> > return xsm_default_action(XSM_PRIV, current->domain, NULL);
> > }
> > }
> > +
> > +static XSM_INLINE int xsm_domain_resource_map(XSM_DEFAULT_ARG
> struct domain *d)
> > +{
> > + XSM_ASSERT_ACTION(XSM_DM_PRIV);
> > + return xsm_default_action(action, current->domain, d);
> > +}
>
> Perhaps better place this near something similar/related (also for
> some of the other additions further down)?
Ok.
Paul
>
> Jan
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