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From 9fdb4f17656f74b35af0882b558e44832ff00b5f Mon Sep 17 00:00:00 2001
From: Jan Beulich <jbeulich@suse.com>
Date: Mon, 31 Oct 2022 13:24:33 +0100
Subject: [PATCH 35/87] 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 <andrew.cooper3@citrix.com>
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 <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
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 3b0d781991b5..1de0139742f7 100644
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -943,8 +943,9 @@ 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);
@@ -1034,8 +1035,9 @@ 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
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