[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 1/2] x86/p2m: fix PoD accounting in guest_physmap_add_entry()
The initial observation was that the mfn_valid() check comes too late: Neither mfn_add() nor mfn_to_page() (let alone de-referencing the result of the latter) are valid for MFNs failing this check. Move it up and - noticing that there's no caller doing so - also add an assertion that this should never produce "false" here. In turn this would have meant that the "else" to that if() could now go away, which didn't seem right at all. And indeed, considering callers like memory_exchange() or various grant table functions, the PoD accounting should have been outside of that if() from the very beginning. Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -883,6 +883,12 @@ guest_physmap_add_entry(struct domain *d if ( p2m_is_foreign(t) ) return -EINVAL; + if ( !mfn_valid(mfn) ) + { + ASSERT_UNREACHABLE(); + return -EINVAL; + } + p2m_lock(p2m); P2M_DEBUG("adding gfn=%#lx mfn=%#lx\n", gfn_x(gfn), mfn_x(mfn)); @@ -984,12 +990,13 @@ guest_physmap_add_entry(struct domain *d } /* Now, actually do the two-way mapping */ - if ( mfn_valid(mfn) ) + rc = p2m_set_entry(p2m, gfn, mfn, page_order, t, p2m->default_access); + if ( rc == 0 ) { - rc = p2m_set_entry(p2m, gfn, mfn, page_order, t, - p2m->default_access); - if ( rc ) - goto out; /* Failed to update p2m, bail without updating m2p. */ + pod_lock(p2m); + p2m->pod.entry_count -= pod_count; + BUG_ON(p2m->pod.entry_count < 0); + pod_unlock(p2m); if ( !p2m_is_grant(t) ) { @@ -998,20 +1005,6 @@ guest_physmap_add_entry(struct domain *d gfn_x(gfn_add(gfn, i))); } } - else - { - gdprintk(XENLOG_WARNING, "Adding bad mfn to p2m map (%#lx -> %#lx)\n", - gfn_x(gfn), mfn_x(mfn)); - rc = p2m_set_entry(p2m, gfn, INVALID_MFN, page_order, - p2m_invalid, p2m->default_access); - if ( rc == 0 ) - { - pod_lock(p2m); - p2m->pod.entry_count -= pod_count; - BUG_ON(p2m->pod.entry_count < 0); - pod_unlock(p2m); - } - } out: p2m_unlock(p2m); _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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