Messages in this thread | | | Date | Mon, 6 Jun 2022 09:34:50 +0800 | Subject | Re: [PATCH 09/12] iommu/vt-d: Check device list of domain in domain free path | From | Baolu Lu <> |
| |
On 2022/6/2 14:29, Tian, Kevin wrote: >> From: Baolu Lu <baolu.lu@linux.intel.com> >> Sent: Wednesday, June 1, 2022 7:02 PM >> >> On 2022/6/1 17:28, Tian, Kevin wrote: >>>> From: Lu Baolu <baolu.lu@linux.intel.com> >>>> Sent: Friday, May 27, 2022 2:30 PM >>>> >>>> When the IOMMU domain is about to be freed, it should not be set on >> any >>>> device. Instead of silently dealing with some bug cases, it's better to >>>> trigger a warning to report and fix any potential bugs at the first time. >>>> >>> >>> >>>> static void domain_exit(struct dmar_domain *domain) >>>> { >>>> - >>>> - /* Remove associated devices and clear attached or cached domains >>>> */ >>>> - domain_remove_dev_info(domain); >>>> + if (WARN_ON(!list_empty(&domain->devices))) >>>> + return; >>>> >>> >>> warning is good but it doesn't mean the driver shouldn't deal with >>> that situation to make it safer e.g. blocking DMA from all attached >>> device... >> >> I have ever thought the same thing. :-) >> >> Blocking DMA from attached device should be done when setting blocking >> domain to the device. It should not be part of freeing a domain. > > yes but here we are talking about some bug scenario. > >> >> Here, the caller asks the driver to free the domain, but the driver >> finds that something is wrong. Therefore, it warns and returns directly. >> The domain will still be there in use until the next set_domain(). >> > > at least it'd look safer if we always try to unmap the entire domain i.e.: > > static void domain_exit(struct dmar_domain *domain) > { > - > - /* Remove associated devices and clear attached or cached domains */ > - domain_remove_dev_info(domain); > > if (domain->pgd) { > LIST_HEAD(freelist); > > domain_unmap(domain, 0, DOMAIN_MAX_PFN(domain->gaw), &freelist); > put_pages_list(&freelist); > } > > + if (WARN_ON(!list_empty(&domain->devices))) > + return; > > kfree(domain); > }
Fair enough. Removing all mappings is safer.
Best regards, baolu
| |