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Tsirkin" To: CLEMENT MATHIEU--DRIF Cc: "qemu-devel@nongnu.org" , "jasowang@redhat.com" , "zhenzhong.duan@intel.com" , "kevin.tian@intel.com" , "yi.l.liu@intel.com" , "peterx@redhat.com" , Stefan Hajnoczi Subject: Re: [PATCH] intel_iommu: Take the bql before registering a new address space Message-ID: <20250415025138-mutt-send-email-mst@kernel.org> References: <20250415061353.185589-1-clement.mathieu--drif@eviden.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250415061353.185589-1-clement.mathieu--drif@eviden.com> Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Apr 15, 2025 at 06:18:08AM +0000, CLEMENT MATHIEU--DRIF wrote: > Address space creation might end up being called without holding the > bql as it is exposed through the IOMMU ops. > > Signed-off-by: Clement Mathieu--Drif Indeed, and this can maybe explain some failures we are seeing ... But is it just this part? For example, is access to vtd_address_spaces safe? > --- > hw/i386/intel_iommu.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c > index dffd7ee885..fea2220013 100644 > --- a/hw/i386/intel_iommu.c > +++ b/hw/i386/intel_iommu.c > @@ -4216,6 +4216,7 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, > vtd_dev_as = g_hash_table_lookup(s->vtd_address_spaces, &key); > if (!vtd_dev_as) { > struct vtd_as_key *new_key = g_malloc(sizeof(*new_key)); > + bool take_bql = !bql_locked(); > > new_key->bus = bus; > new_key->devfn = devfn; > @@ -4238,6 +4239,11 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, > vtd_dev_as->context_cache_entry.context_cache_gen = 0; > vtd_dev_as->iova_tree = iova_tree_new(); > > + /* Some functions in this branch require the bql, make sure we own it */ > + if (take_bql) { > + bql_lock(); > + } > + > memory_region_init(&vtd_dev_as->root, OBJECT(s), name, UINT64_MAX); > address_space_init(&vtd_dev_as->as, &vtd_dev_as->root, "vtd-root"); > > @@ -4305,6 +4311,10 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *s, PCIBus *bus, > > vtd_switch_address_space(vtd_dev_as); > > + if (take_bql) { > + bql_unlock(); > + } > + > g_hash_table_insert(s->vtd_address_spaces, new_key, vtd_dev_as); > } > return vtd_dev_as; > -- > 2.49.0