linux-kernel - RE: [PATCH 1/1] iommu/vt-d: Fix possible recursive locking in intel_iommu

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Message-ID: <BN9PR11MB52765FEEC0ED0EAB5D691FA38C959@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Mon, 25 Jul 2022 07:40:22 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>
CC:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        "Robin Murphy" <robin.murphy@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/1] iommu/vt-d: Fix possible recursive locking in
 intel_iommu_init()

> From: Baolu Lu <baolu.lu@...ux.intel.com>
> Sent: Sunday, July 24, 2022 11:00 AM
> 
> Hi Kevin,
> 
> On 2022/7/21 15:39, Tian, Kevin wrote:
> >> From: Lu Baolu <baolu.lu@...ux.intel.com>
> >> Sent: Tuesday, July 19, 2022 7:53 AM
> >>
> >> @@ -88,7 +89,8 @@ extern struct list_head dmar_drhd_units;
> >>   static inline bool dmar_rcu_check(void)
> >>   {
> >>   	return rwsem_is_locked(&dmar_global_lock) ||
> >> -	       system_state == SYSTEM_BOOTING;
> >> +	       system_state == SYSTEM_BOOTING ||
> >> +	       (IS_ENABLED(CONFIG_INTEL_IOMMU)
> >> && !intel_iommu_enabled);
> >>   }
> >
> > intel_iommu_enabled is 0 if CONFIG_INTEL_IOMMU is not set.
> >
> > same for other similar checks.
> 
> Sorry that I didn't get your point. If CONFIG_INTEL_IOMMU is not set,
> IS_ENABLED(CONFIG_INTEL_IOMMU) is 0. The adding check has no effect.
> Did
> I miss anything?
> 

My point was that the check on CONFIG_INTEL_IOMMU is unnecessary.