From: Julien Grall <julien@xen.org>
To: xen-devel@lists.xenproject.org
Cc: hongyxia@amazon.co.uk, iwj@xenproject.org,
Julien Grall <jgrall@amazon.com>, Jan Beulich <jbeulich@suse.com>,
Paul Durrant <paul@xen.org>
Subject: [for-4.15][PATCH v3 3/3] xen/iommu: x86: Harden the IOMMU page-table allocator
Date: Wed, 17 Feb 2021 14:24:58 +0000 [thread overview]
Message-ID: <20210217142458.3769-4-julien@xen.org> (raw)
In-Reply-To: <20210217142458.3769-1-julien@xen.org>
From: Julien Grall <jgrall@amazon.com>
At the moment, we are assuming that only iommu_map() can allocate
IOMMU page-table.
Given the complexity of the IOMMU framework, it would be sensible to
have a check closer to the IOMMU allocator. This would avoid to leak
IOMMU page-tables again in the future.
iommu_alloc_pgtable() is now checking if the domain is dying before
adding the page in the list. We are relying on &hd->arch.pgtables.lock
to synchronize d->is_dying.
Take the opportunity to add an ASSERT() in arch_iommu_domain_destroy()
to check if we freed all the IOMMU page tables.
Signed-off-by: Julien Grall <jgrall@amazon.com>
---
Changes in v3:
- Rename the patch. This was originally "xen/iommu: x86: Don't leak
the IOMMU page-tables"
- Rework the commit message
- Move the patch towards the end of the series
Changes in v2:
- Rework the approach
- Move the patch earlier in the series
---
xen/drivers/passthrough/x86/iommu.c | 33 ++++++++++++++++++++++++++++-
1 file changed, 32 insertions(+), 1 deletion(-)
diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c
index faa0078db595..a67075f0045d 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -149,6 +149,13 @@ int arch_iommu_domain_init(struct domain *d)
void arch_iommu_domain_destroy(struct domain *d)
{
+ /*
+ * There should be not page-tables left allocated by the time the
+ * domain is destroyed. Note that arch_iommu_domain_destroy() is
+ * called unconditionally, so pgtables may be unitialized.
+ */
+ ASSERT(dom_iommu(d)->platform_ops == NULL ||
+ page_list_empty(&dom_iommu(d)->arch.pgtables.list));
}
static bool __hwdom_init hwdom_iommu_map(const struct domain *d,
@@ -279,6 +286,9 @@ int iommu_free_pgtables(struct domain *d)
*/
hd->platform_ops->clear_root_pgtable(d);
+ /* After this barrier no new page allocations can occur. */
+ spin_barrier(&hd->arch.pgtables.lock);
+
while ( (pg = page_list_remove_head(&hd->arch.pgtables.list)) )
{
free_domheap_page(pg);
@@ -296,6 +306,7 @@ struct page_info *iommu_alloc_pgtable(struct domain *d)
unsigned int memflags = 0;
struct page_info *pg;
void *p;
+ bool alive = false;
#ifdef CONFIG_NUMA
if ( hd->node != NUMA_NO_NODE )
@@ -315,9 +326,29 @@ struct page_info *iommu_alloc_pgtable(struct domain *d)
unmap_domain_page(p);
spin_lock(&hd->arch.pgtables.lock);
- page_list_add(pg, &hd->arch.pgtables.list);
+ /*
+ * The IOMMU page-tables are freed when relinquishing the domain, but
+ * nothing prevent allocation to happen afterwards. There is no valid
+ * reasons to continue to update the IOMMU page-tables while the
+ * domain is dying.
+ *
+ * So prevent page-table allocation when the domain is dying.
+ *
+ * We relying on &hd->arch.pgtables.lock to synchronize d->is_dying.
+ */
+ if ( likely(!d->is_dying) )
+ {
+ alive = true;
+ page_list_add(pg, &hd->arch.pgtables.list);
+ }
spin_unlock(&hd->arch.pgtables.lock);
+ if ( unlikely(!alive) )
+ {
+ free_domheap_page(pg);
+ pg = NULL;
+ }
+
return pg;
}
--
2.17.1
next prev parent reply other threads:[~2021-02-17 14:25 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 14:24 [for-4.15][PATCH v3 0/3] xen/iommu: Collection of bug fixes for IOMMU teadorwn Julien Grall
2021-02-17 14:24 ` [for-4.15][PATCH v3 1/3] xen/iommu: x86: Clear the root page-table before freeing the page-tables Julien Grall
2021-02-17 14:54 ` Jan Beulich
2021-02-17 15:00 ` Julien Grall
2021-02-17 15:17 ` Jan Beulich
2021-02-17 16:48 ` Julien Grall
2021-02-17 14:24 ` [for-4.15][PATCH v3 2/3] xen/x86: iommu: Ignore IOMMU mapping requests when a domain is dying Julien Grall
2021-02-17 15:01 ` Jan Beulich
2021-02-17 16:07 ` Julien Grall
2021-02-18 13:05 ` Jan Beulich
2021-02-18 13:25 ` Julien Grall
2021-02-19 8:49 ` Jan Beulich
2021-02-19 9:24 ` Julien Grall
2021-02-18 14:00 ` Paul Durrant
2021-02-19 8:56 ` Jan Beulich
2021-02-17 14:24 ` Julien Grall [this message]
2021-02-17 15:13 ` [for-4.15][PATCH v3 3/3] xen/iommu: x86: Harden the IOMMU page-table allocator Jan Beulich
2021-02-17 16:29 ` Julien Grall
2021-02-18 13:10 ` Jan Beulich
2021-02-18 13:19 ` Julien Grall
2021-02-18 17:04 ` Jan Beulich
2021-02-18 17:41 ` Julien Grall
2021-02-19 8:46 ` Jan Beulich
2021-02-19 8:57 ` Julien Grall
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