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Wed, 16 Apr 2025 02:09:34 -0700 (PDT) Received: from draig.lan ([185.126.160.109]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5f36f5056c4sm8402555a12.62.2025.04.16.02.09.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 16 Apr 2025 02:09:34 -0700 (PDT) Received: from draig (localhost [IPv6:::1]) by draig.lan (Postfix) with ESMTP id 859DB5F846; Wed, 16 Apr 2025 10:09:33 +0100 (BST) From: =?utf-8?Q?Alex_Benn=C3=A9e?= 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" , "mst@redhat.com" Subject: Re: [PATCH v2] intel_iommu: Take the bql before registering a new address space In-Reply-To: <20250415153207.372427-1-clement.mathieu--drif@eviden.com> (CLEMENT MATHIEU--DRIF's message of "Tue, 15 Apr 2025 15:32:38 +0000") References: <20250415153207.372427-1-clement.mathieu--drif@eviden.com> User-Agent: mu4e 1.12.9; emacs 30.1 Date: Wed, 16 Apr 2025 10:09:33 +0100 Message-ID: <87plhccw1e.fsf@draig.linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=2a00:1450:4864:20::531; envelope-from=alex.bennee@linaro.org; helo=mail-ed1-x531.google.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, 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_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no 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 CLEMENT MATHIEU--DRIF writes: > 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 | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c > index dffd7ee885..3df7a7489b 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 =3D g_hash_table_lookup(s->vtd_address_spaces, &key); > if (!vtd_dev_as) { > struct vtd_as_key *new_key =3D g_malloc(sizeof(*new_key)); > + bool take_bql =3D !bql_locked(); >=20=20 > new_key->bus =3D bus; > new_key->devfn =3D devfn; > @@ -4238,6 +4239,14 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *= s, PCIBus *bus, > vtd_dev_as->context_cache_entry.context_cache_gen =3D 0; > vtd_dev_as->iova_tree =3D iova_tree_new(); >=20=20 > + /* > + * memory_region_add_subregion_overlap requires the bql, > + * make sure we own it. > + */ > + if (take_bql) { > + bql_lock(); > + } > + Using BQL_LOCK_GUARD(); here will auto clean-up as we exit and it handles the nested BQL state as well. > memory_region_init(&vtd_dev_as->root, OBJECT(s), name, UINT64_MA= X); > address_space_init(&vtd_dev_as->as, &vtd_dev_as->root, "vtd-root= "); >=20=20 > @@ -4305,6 +4314,10 @@ VTDAddressSpace *vtd_find_add_as(IntelIOMMUState *= s, PCIBus *bus, >=20=20 > vtd_switch_address_space(vtd_dev_as); >=20=20 > + if (take_bql) { > + bql_unlock(); > + } > + > g_hash_table_insert(s->vtd_address_spaces, new_key, vtd_dev_as); > } > return vtd_dev_as; --=20 Alex Benn=C3=A9e Virtualisation Tech Lead @ Linaro