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Tsirkin" To: CLEMENT MATHIEU--DRIF Cc: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , "qemu-devel@nongnu.org" , "jasowang@redhat.com" , "zhenzhong.duan@intel.com" , "kevin.tian@intel.com" , "yi.l.liu@intel.com" , "peterx@redhat.com" Subject: Re: [PATCH] intel_iommu: Take the bql before registering a new address space Message-ID: <20250415034112-mutt-send-email-mst@kernel.org> References: <20250415061353.185589-1-clement.mathieu--drif@eviden.com> <23c9f066-f30c-4e35-8629-504eeb9cd7a8@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=170.10.133.124; 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_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, 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 07:28:34AM +0000, CLEMENT MATHIEU--DRIF wrote: > > > On 15/04/2025 8:53 am, Philippe Mathieu-Daudé wrote: > > Caution: External email. Do not open attachments or click links, unless > > this email comes from a known sender and you know the content is safe. > > > > > > On 15/4/25 08:18, 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 > >> --- > >>   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); > > > > Would it help clarifying to propagate this argument down? > > vtd_switch_address_space(VTDAddressSpace *as, bool need_lock); > > Hi phil, vtd_switch_address_space already does the same kind of check > > > > >> > >> +        if (take_bql) { > >> +            bql_unlock(); > >> +        } > >> + > >>           g_hash_table_insert(s->vtd_address_spaces, new_key, > >> vtd_dev_as); > >>       } > >>       return vtd_dev_as; > > As an apropos, I think any caller of bql_lock really should call bql_lock_impl so we know who took BQL. Or just use BQL_LOCK_GUARD. But, that's an unrelated cleanup.