Messages in this thread | | | Subject | Re: [PATCH] iommu: intel: remove flooding of non-error logs, when new-DMA-PTE is the same as old-DMA-PTE. | From | Lu Baolu <> | Date | Sat, 2 Oct 2021 21:14:48 +0800 |
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On 2021/10/2 20:40, Ajay Garg wrote: > Taking a SD-MMC controller (over PCI) as an example, following is an > example sequencing, where the log-flooding happened : > > 0. > We have a host and a guest, both running latest x86_64 kernels. > > 1. > Host-machine is booted up (with intel_iommu=on), and the DMA-PTEs > are setup for the controller (on the host), for the first time. > > 2. > The SD-controller device is added to a (L1) guest on a KVM-VM > (via virt-manager).
Isn't the domain should be switched from a default domain to an unmanaged domain when the device is assigned to the guest?
Even you want to r-setup the same mappings, you need to un-map all existing mappings, right?
Best regards, baolu
> > 3. > The KVM-VM is booted up. > > 4. > Above triggers a re-setup of DMA-PTEs on the host, for a > second time. > > It is observed that the new PTEs formed (on the host) are same > as the original PTEs, and thus following logs, accompanied by > stacktraces, overwhelm the logs : > > ...... > DMAR: ERROR: DMA PTE for vPFN 0x428ec already set (to 3f6ec003 not 3f6ec003) > DMAR: ERROR: DMA PTE for vPFN 0x428ed already set (to 3f6ed003 not 3f6ed003) > DMAR: ERROR: DMA PTE for vPFN 0x428ee already set (to 3f6ee003 not 3f6ee003) > DMAR: ERROR: DMA PTE for vPFN 0x428ef already set (to 3f6ef003 not 3f6ef003) > DMAR: ERROR: DMA PTE for vPFN 0x428f0 already set (to 3f6f0003 not 3f6f0003) > ...... > > As the PTEs are same, so there is no cause of concern, and we can easily > avoid the logs-flood for this non-error case. > > Signed-off-by: Ajay Garg <ajaygargnsit@gmail.com> > --- > drivers/iommu/intel/iommu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c > index d75f59ae28e6..8bea8b4e3ff9 100644 > --- a/drivers/iommu/intel/iommu.c > +++ b/drivers/iommu/intel/iommu.c > @@ -2370,7 +2370,7 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn, > * touches the iova range > */ > tmp = cmpxchg64_local(&pte->val, 0ULL, pteval); > - if (tmp) { > + if (tmp && (tmp != pteval)) { > static int dumps = 5; > pr_crit("ERROR: DMA PTE for vPFN 0x%lx already set (to %llx not %llx)\n", > iov_pfn, tmp, (unsigned long long)pteval); >
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