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([2001:871:22a:693f::1ad1]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-502a1ed3155sm2097251cf.19.2026.01.15.11.02.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 15 Jan 2026 11:02:06 -0800 (PST) Message-ID: <5cab0953-c2a3-4baa-af91-e9519afef092@gmail.com> Date: Thu, 15 Jan 2026 20:02:02 +0100 Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [REGRESSION] qcom: iommu: nullpointer dereference on boot on apq8064 To: Robin Murphy , Jason Gunthorpe Cc: Konrad Dybcio , Dmitry Baryshkov , Rob Clark , Matti Vaittinen , iommu@lists.linux.dev, linux-arm-msm@vger.kernel.org, Rudraksha Gupta References: <569d7de2-cfcd-4d28-8bbf-14a0179f665e@gmail.com> <20260105180213.GG125261@ziepe.ca> <9a86120e-c0be-4ed5-a3de-cc7f164da154@arm.com> Content-Language: en-US, de-DE From: Christian Schrefl In-Reply-To: <9a86120e-c0be-4ed5-a3de-cc7f164da154@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Hi Robin, On 1/6/26 7:50 PM, Robin Murphy wrote: > On 2026-01-05 6:02 pm, Jason Gunthorpe wrote: >> Though this looks really weird: >> >>          struct msm_iommu_ctx_dev *master = dev_iommu_priv_get(dev); >>          int sid; >> >>          if (list_empty(&(*iommu)->ctx_list)) { >>                  master = kzalloc(sizeof(*master), GFP_ATOMIC); >> >> So maybe master is NULL and !list_empty()? > > AFAICS that could happen if of_xlate has run once, and then for whatever > reason dev->iommu is torn down and the whole process started from > scratch a second time - although I'm struggling to see any obvious cause > for that in the absence of any other visible errors or async probe > races (and assuming that the IOMMUs on this platform ever actually > worked at all, of course...) > > However it certainly stands out as a bit wrong that of_xlate is touching > the IOMMU instance itself - that should never have been expected to work > well. Does the diff below help? > > Thanks, > Robin. > > ----->8----- > diff --git a/drivers/iommu/msm_iommu.c b/drivers/iommu/msm_iommu.c > index 819add75a665..e57780fc3287 100644 > --- a/drivers/iommu/msm_iommu.c > +++ b/drivers/iommu/msm_iommu.c > @@ -360,14 +360,11 @@ static int msm_iommu_domain_config(struct msm_priv *priv) >  /* Must be called under msm_iommu_lock */ >  static struct msm_iommu_dev *find_iommu_for_dev(struct device *dev) >  { > +    struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev); >      struct msm_iommu_dev *iommu, *ret = NULL; > -    struct msm_iommu_ctx_dev *master; >   >      list_for_each_entry(iommu, &qcom_iommu_devices, dev_node) { > -        master = list_first_entry(&iommu->ctx_list, > -                      struct msm_iommu_ctx_dev, > -                      list); > -        if (master->of_node == dev->of_node) { > +        if (iommu->dev->fwnode == fwspec->iommu_fwnode) { >              ret = iommu; >              break; >          } > @@ -378,6 +375,7 @@ static struct msm_iommu_dev *find_iommu_for_dev(struct device *dev) >   >  static struct iommu_device *msm_iommu_probe_device(struct device *dev) >  { > +    struct msm_iommu_ctx_dev *master; >      struct msm_iommu_dev *iommu; >      unsigned long flags; >   > @@ -388,6 +386,8 @@ static struct iommu_device *msm_iommu_probe_device(struct device *dev) >      if (!iommu) >          return ERR_PTR(-ENODEV); >   > +    master = dev_iommu_priv_get(dev); > +    list_add(&master->list, &iommu->ctx_list); >      return &iommu->iommu; >  } >   > @@ -604,14 +604,13 @@ static int insert_iommu_master(struct device *dev, >      struct msm_iommu_ctx_dev *master = dev_iommu_priv_get(dev); >      int sid; >   > -    if (list_empty(&(*iommu)->ctx_list)) { > +    if (!master) { >          master = kzalloc(sizeof(*master), GFP_ATOMIC); >          if (!master) { >              dev_err(dev, "Failed to allocate iommu_master\n"); >              return -ENOMEM; >          } >          master->of_node = dev->of_node; > -        list_add(&master->list, &(*iommu)->ctx_list); >          dev_iommu_priv_set(dev, master); >      } >   Sorry for taking so long until I got to trying it out. The patch fixes the crash! Cheers, Christian