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Posted to commits@nuttx.apache.org by GitBox <gi...@apache.org> on 2020/05/05 07:35:46 UTC

[GitHub] [incubator-nuttx] sonicyang opened a new pull request #973: x86_64: Fix crash around enabling XSAVE and SSE/AVX

sonicyang opened a new pull request #973:
URL: https://github.com/apache/incubator-nuttx/pull/973


   ## Summary
   
   If the user chooses to enable SSE related function in config, the OS will check and initialize the FPU during boot.
   
   During the setup of FPU, the LDMXCSR instruction takes a 32 bit memory address, containing the FPU setting. The FPU setting is hardcoded and placed in the binary image.
   
   However, this is conducted after the kernel's lower memoey mapping was revoked, causing a page fault.
   Using the high address of the hardcoded FPU setting is not possible because the kernel is mapped above 4GB space (32bit).
   
   The proposed fix it by revoking the lower 128MB mapping at a later stage of booting, after the setup procedure is conducted.
   
   ## Impact
   
   No more instant crash during boot with SSE/AVX enabled.
   
   ## Testing
   
   Should boot on bochs/qemu with ostest
   


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[GitHub] [incubator-nuttx] btashton commented on pull request #973: x86_64: Fix crash around enabling XSAVE and SSE/AVX

Posted by GitBox <gi...@apache.org>.
btashton commented on pull request #973:
URL: https://github.com/apache/incubator-nuttx/pull/973#issuecomment-623919625


   This seems like it might be resolving one of the intermittent crashes I was seeing.  Looks good, I'll merge when all the test pass.


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