Messages in this thread | | | Date | Tue, 17 May 2022 08:13:50 -0300 | From | Jason Gunthorpe <> | Subject | Re: [PATCH 6/7] x86/boot/tboot: Move tboot_force_iommu() to Intel IOMMU |
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On Tue, May 17, 2022 at 10:05:43AM +0800, Baolu Lu wrote: > Hi Jason, > > On 2022/5/17 02:06, Jason Gunthorpe wrote: > > > +static __init int tboot_force_iommu(void) > > > +{ > > > + if (!tboot_enabled()) > > > + return 0; > > > + > > > + if (no_iommu || dmar_disabled) > > > + pr_warn("Forcing Intel-IOMMU to enabled\n"); > > Unrelated, but when we are in the special secure IOMMU modes, do we > > force ATS off? Specifically does the IOMMU reject TLPs that are marked > > as translated? > > Good question. From IOMMU point of view, I don't see a point to force > ATS off, but trust boot involves lots of other things that I am not > familiar with. Anybody else could help to answer?
ATS is inherently not secure, if a rouge device can issue a TLP with the translated bit set then it has unlimited access to host memory.
Many of these trusted iommu scenarios rely on the idea that a rouge device cannot DMA to arbitary system memory.
Jason
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