Messages in this thread | | | Subject | Re: [PATCH v2 3/4] drm/ttm, drm/vmwgfx: Correctly support support AMD memory encryption | From | Dave Hansen <> | Date | Tue, 3 Sep 2019 12:38:25 -0700 |
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This whole thing looks like a fascinating collection of hacks. :)
ttm is taking a stack-alllocated "VMA" and handing it to vmf_insert_*() which obviously are expecting "real" VMAs that are linked into the mm. It's extracting some pgprot_t information from the real VMA, making a psuedo-temporary VMA, then passing the temporary one back into the insertion functions:
> static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf) > { ... > struct vm_area_struct cvma; ... > if (vma->vm_flags & VM_MIXEDMAP) > ret = vmf_insert_mixed(&cvma, address, > __pfn_to_pfn_t(pfn, PFN_DEV)); > else > ret = vmf_insert_pfn(&cvma, address, pfn);
I can totally see why this needs new exports. But, man, it doesn't seem like something we want to keep *feeding*.
The real problem here is that the encryption bits from the device VMA's "true" vma->vm_page_prot don't match the ones that actually get inserted, probably because the device ptes need the encryption bits cleared but the system memory PTEs need them set *and* they're mixed under one VMA.
The thing we need to stop is having mixed encryption rules under one VMA.
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