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Re: [Xen-devel] [PATCH v3] x86/HVM: Merge HVM and PVH hypercall tables

On 12/18/2015 12:16 PM, Andrew Cooper wrote:
On 18/12/15 17:10, Jan Beulich wrote:
On 18.12.15 at 17:59, <andrew.cooper3@xxxxxxxxxx> wrote:
On 18/12/15 16:37, Jan Beulich wrote:
On 18.12.15 at 17:28, <andrew.cooper3@xxxxxxxxxx> wrote:
On 17/12/15 23:00, Boris Ostrovsky wrote:
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index a7767f8..871aca0 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -3019,6 +3019,25 @@ long do_mmuext_op(
+ if ( has_hvm_container_domain(d) )
+        {
+            switch ( op.cmd )
+            {
+            case MMUEXT_PIN_L1_TABLE:
+            case MMUEXT_PIN_L2_TABLE:
+            case MMUEXT_PIN_L3_TABLE:
+            case MMUEXT_PIN_L4_TABLE:
+            case MMUEXT_UNPIN_TABLE:
+                if ( is_control_domain(d) )
+                    break;
This needs to be an XSM check, rather than a dom0 check.  Consider the
usecase of a PVH/DMLite domain builder stubdomain.
But wouldn't that be the control domain then? Afaict by making this
an XSM check we'd also permit the hardware domain access to these,
for no reason. In fact we should probably further restrict this to
d != pg_owner.
Any domain needing to construct PV domains needs to be able to make
these hypercalls against the target domain.

Therefore, the only valid check is whether XSM will permit 'current' to
issue the hypercall against 'd', irrespective of whether current is the
control domain, the hardware domain, or something else.

I think all that is needed is xsm_mmuext_op(XSM_TARGET, d, pg_owner)
Which, as Boris has just pointed out, is already there.
So it is.  That is good.

But which also allows the d to issue such operations on itself.

Won't get_pg_owner() fail in that case? (domid == curr->domain_id)  test?

For safely sake, it is probably having either do_mmuext_op() or the XSM
hook bail early if d is not a PV guest.

I would hesitate at putting that check inside the hvm conditional at
this point.

I am not sure what you meant here.


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