Messages in this thread | | | From | "Tian, Kevin" <> | Subject | RE: [PATCH 09/12] iommu/vt-d: Check device list of domain in domain free path | Date | Thu, 2 Jun 2022 06:29:42 +0000 |
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> 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); }
Thanks Kevin
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