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envelope-from=yi.l.liu@intel.com; helo=mgamail.intel.com X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 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_MED=-2.3, 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 2025/4/15 16:03, Philippe Mathieu-Daudé wrote: > On 15/4/25 09:42, Michael S. Tsirkin wrote: >> 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. >> > > Yeah unrelated cleanup. Although I don't understand why these > code paths don't use memory_region_transaction_begin/commit and > have to access BQL. The below two functions would call memory_region_transaction_begin/commit(). So these paths need BQL. memory_region_set_enabled() memory_region_add_subregion_overlap() -- Regards, Yi Liu