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This can be fixed in the run-time by book >> keeping the ranges and doing unmapping/mapping. I guess this goes >> beyond what mm should support? >> >> I thought to plain check this as it has been two years since my last >> query on topic (if we could improve either the driver or mm somehow). > > In the past I've substituted kernel's mm merge code with user space > replacement: > > https://github.com/enarx/mmledger/blob/main/src/lib.rs > > It's essentially a reimplementation of al stuff that goes into > mm/mmap.c's vma_merge(). I cannot recall anymore whether merges > which map over existing ranges were working correctly, i.e. was > the issue only concerning adjacent VMA's. > > What I'm looking here is that can we make some cosntraints that > if satisfied by the pfnmap code, it could leverage the code from > vma_merge(). Perhaps by making explicit call to vma_merge()? > I get that implicit use moves too much responsibility to the mm > subsystem. > Hi Jarkko, Just want to understand more on the background: Are you seeing any real problem due to needing a lot of mmap()s to the same enclave, or it is just a problem that doesn't look nice and you want to resolve? I mean, this problem doesn't seem to be SGX-specific but a common one for VMAs with VM_PFNMAP (any bit in VM_SPECIAL), e.g., from random device drivers with mmap() support. We will need a good justification if we want to make any core-mm change, if any, for this.