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Thu, 28 Dec 2023 08:38:51 +0000 Received: from BN9PR11MB5276.namprd11.prod.outlook.com ([fe80::a8e9:c80f:9484:f7cb]) by BN9PR11MB5276.namprd11.prod.outlook.com ([fe80::a8e9:c80f:9484:f7cb%3]) with mapi id 15.20.7113.028; Thu, 28 Dec 2023 08:38:50 +0000 From: "Tian, Kevin" To: Ethan Zhao , "bhelgaas@google.com" , "baolu.lu@linux.intel.com" , "dwmw2@infradead.org" , "will@kernel.org" , "robin.murphy@arm.com" , "lukas@wunner.de" CC: "linux-pci@vger.kernel.org" , "iommu@lists.linux.dev" , "linux-kernel@vger.kernel.org" Subject: RE: [RFC PATCH v9 5/5] iommu/vt-d: don't loop for timeout ATS Invalidation request forever Thread-Topic: [RFC PATCH v9 5/5] iommu/vt-d: don't loop for timeout ATS Invalidation request forever Thread-Index: AQHaOSNeLqk7OMC1FUmomOwsRPnbNLC+Xgtw Date: Thu, 28 Dec 2023 08:38:50 +0000 Message-ID: References: <20231228001646.587653-1-haifeng.zhao@linux.intel.com> <20231228001646.587653-6-haifeng.zhao@linux.intel.com> In-Reply-To: <20231228001646.587653-6-haifeng.zhao@linux.intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=intel.com; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: BN9PR11MB5276.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: ab7ea261-a750-4b16-44b1-08dc07806ad2 X-MS-Exchange-CrossTenant-originalarrivaltime: 28 Dec 2023 08:38:50.8939 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: uE0APQzuBo0btI50QBu8Pw0EXyC4BAwJGKOvonjQVpzluQKtmqbSsT/pHVsV08jeotOpUUV8FS3L7BbwcHr9bA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH0PR11MB5330 X-OriginatorOrg: intel.com > From: Ethan Zhao > Sent: Thursday, December 28, 2023 8:17 AM >=20 > When the ATS Invalidation request timeout happens, the qi_submit_sync() > will restart and loop for the invalidation request forever till it is > done, it will block another Invalidation thread such as the fq_timer > to issue invalidation request, cause the system lockup as following >=20 > [exception RIP: native_queued_spin_lock_slowpath+92] >=20 > RIP: ffffffffa9d1025c RSP: ffffb202f268cdc8 RFLAGS: 00000002 >=20 > RAX: 0000000000000101 RBX: ffffffffab36c2a0 RCX: 0000000000000000 >=20 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffab36c2a0 >=20 > RBP: ffffffffab36c2a0 R8: 0000000000000001 R9: 0000000000000000 >=20 > R10: 0000000000000010 R11: 0000000000000018 R12: 0000000000000000 >=20 > R13: 0000000000000004 R14: ffff9e10d71b1c88 R15: ffff9e10d71b1980 >=20 > ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 >=20 > #12 [ffffb202f268cdc8] native_queued_spin_lock_slowpath at > ffffffffa9d1025c >=20 > #13 [ffffb202f268cdc8] do_raw_spin_lock at ffffffffa9d121f1 >=20 > #14 [ffffb202f268cdd8] _raw_spin_lock_irqsave at ffffffffaa51795b >=20 > #15 [ffffb202f268cdf8] iommu_flush_dev_iotlb at ffffffffaa20df48 >=20 > #16 [ffffb202f268ce28] iommu_flush_iova at ffffffffaa20e182 >=20 > #17 [ffffb202f268ce60] iova_domain_flush at ffffffffaa220e27 >=20 > #18 [ffffb202f268ce70] fq_flush_timeout at ffffffffaa221c9d >=20 > #19 [ffffb202f268cea8] call_timer_fn at ffffffffa9d46661 >=20 > #20 [ffffb202f268cf08] run_timer_softirq at ffffffffa9d47933 >=20 > #21 [ffffb202f268cf98] __softirqentry_text_start at ffffffffaa8000e0 >=20 > #22 [ffffb202f268cff0] asm_call_sysvec_on_stack at ffffffffaa60114f > --- --- > (the left part of exception see the hotplug case of ATS capable device) >=20 > If one endpoint device just no response to the ATS Invalidation request, > but is not gone, it will bring down the whole system, to avoid such > case, don't try the timeout ATS Invalidation request forever. >=20 > Signed-off-by: Ethan Zhao > --- > drivers/iommu/intel/dmar.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c > index 76903a8bf963..206ab0b7294f 100644 > --- a/drivers/iommu/intel/dmar.c > +++ b/drivers/iommu/intel/dmar.c > @@ -1457,7 +1457,7 @@ int qi_submit_sync(struct intel_iommu *iommu, > struct qi_desc *desc, > reclaim_free_desc(qi); > raw_spin_unlock_irqrestore(&qi->q_lock, flags); >=20 > - if (rc =3D=3D -EAGAIN) > + if (rc =3D=3D -EAGAIN && type !=3DQI_DIOTLB_TYPE && type !=3D > QI_DEIOTLB_TYPE) > goto restart; >=20 this change is moot.=20 -EAGAIN is set only when hardware detects a ATS invalidation completion timeout in qi_check_fault(). so above just essentially kills the restart lo= gic. I'd wait for the maintainer of this driver to comment. this part doesn't look good but there might be some history reason so carefulness must be paid.