Since updating PASID (Process Address Space ID) MSR through IPI has a few issues that are beyond repair, Thomas disables ENQCMD [1].
Please check Documentation/x86/sva.rst for various concepts and terms related to PASID, ENQCMD, SVM (Shared Virtual Memory), etc. This series re-enables ENQCMD and IA32_PASID MSR by using a #GP fix up method previously published in [2]. A PASID is allocated to a mm once a SVM is bound to the mm via intel_svm_bind() API. The #GP fix up method updates the PASID MSR from the mm's PASID in #GP handler when one thread in a process executes ENQCMD for the first time and one reference is taken to the PASID. Once the MSR is uploaded, the thread keeps and can use it for the rest life time of the thread. In exit(2) or unbind, the PASID's reference is dropped and the PASID is freed if there is no reference. References: 1. ENQCMD was disabled in upstream due to serious issues: https://lore.kernel.org/linux-iommu/87mtsd6gr9....@nanos.tec.linutronix.de/ 2. #GP fix up PASID MSR: https://lore.kernel.org/linux-iommu/1594684087-61184-1-git-send-email-fenghua...@intel.com/ Fenghua Yu (7): iommu/vt-d: Clean up unused PASID updating functions x86/process: Clear PASID state for a newly forked/cloned thread x86/traps: Demand-populate PASID MSR via #GP x86/mmu: Add mm-based PASID refcounting x86/cpufeatures: Re-enable ENQCMD tools/objtool: Check for use of the ENQCMD instruction in the kernel docs: x86: Change documentation for SVA (Shared Virtual Addressing) Peter Zijlstra (1): sched: Define and initialize a flag to identify valid PASID in the task Documentation/x86/sva.rst | 81 ++++++++++++++++++-- arch/x86/include/asm/disabled-features.h | 7 +- arch/x86/include/asm/fpu/api.h | 6 +- arch/x86/include/asm/iommu.h | 8 ++ arch/x86/include/asm/mmu_context.h | 2 + arch/x86/kernel/fpu/xstate.c | 59 +++++++++++++++ arch/x86/kernel/process.c | 8 ++ arch/x86/kernel/traps.c | 12 +++ drivers/iommu/intel/svm.c | 95 ++++++++++++++++++------ include/linux/sched.h | 4 + kernel/fork.c | 4 + tools/objtool/arch/x86/decode.c | 10 ++- tools/objtool/check.c | 20 +++++ tools/objtool/include/objtool/arch.h | 1 + 14 files changed, 283 insertions(+), 34 deletions(-) -- 2.33.0 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
