From 08bc78b4eecaef33250038f7e484bdf01ea1017c Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 31 Oct 2022 13:35:06 +0100 Subject: [PATCH 075/126] x86/shadow: drop (replace) bogus assertions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The addition of a call to shadow_blow_tables() from shadow_teardown() has resulted in the "no vcpus" related assertion becoming triggerable: If domain_create() fails with at least one page successfully allocated in the course of shadow_enable(), or if domain_create() succeeds and the domain is then killed without ever invoking XEN_DOMCTL_max_vcpus. Note that in-tree tests (test-resource and test-tsx) do exactly the latter of these two. The assertion's comment was bogus anyway: Shadow mode has been getting enabled before allocation of vCPU-s for quite some time. Convert the assertion to a conditional: As long as there are no vCPU-s, there's nothing to blow away. Fixes: e7aa55c0aab3 ("x86/p2m: free the paging memory pool preemptively") Reported-by: Andrew Cooper A similar assertion/comment pair exists in _shadow_prealloc(); the comment is similarly bogus, and the assertion could in principle trigger e.g. when shadow_alloc_p2m_page() is called early enough. Replace those at the same time by a similar early return, here indicating failure to the caller (which will generally lead to the domain being crashed in shadow_prealloc()). Signed-off-by: Jan Beulich Acked-by: Roger Pau Monné Acked-by: Andrew Cooper master commit: a92dc2bb30ba65ae25d2f417677eb7ef9a6a0fef master date: 2022-10-24 15:46:11 +0200 --- xen/arch/x86/mm/shadow/common.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/xen/arch/x86/mm/shadow/common.c b/xen/arch/x86/mm/shadow/common.c index 8f7fddcee1e5..e36d49d1fcba 100644 --- a/xen/arch/x86/mm/shadow/common.c +++ b/xen/arch/x86/mm/shadow/common.c @@ -942,8 +942,9 @@ static bool __must_check _shadow_prealloc(struct domain *d, unsigned int pages) /* No reclaim when the domain is dying, teardown will take care of it. */ return false; - /* Shouldn't have enabled shadows if we've no vcpus. */ - ASSERT(d->vcpu && d->vcpu[0]); + /* Nothing to reclaim when there are no vcpus yet. */ + if ( !d->vcpu[0] ) + return false; /* Stage one: walk the list of pinned pages, unpinning them */ perfc_incr(shadow_prealloc_1); @@ -1033,8 +1034,9 @@ void shadow_blow_tables(struct domain *d) mfn_t smfn; int i; - /* Shouldn't have enabled shadows if we've no vcpus. */ - ASSERT(d->vcpu && d->vcpu[0]); + /* Nothing to do when there are no vcpus yet. */ + if ( !d->vcpu[0] ) + return; /* Pass one: unpin all pinned pages */ foreach_pinned_shadow(d, sp, t) -- 2.37.4