[PATCH v4 00/11] Re-enable ENQCMD and PASID MSR

Fenghua Yu
2022-02-08T01:05:06Z

Problems in the old code to manage SVM (Shared Virtual Memory) devices
and the PASID (Process Address Space ID) led to that code being
disabled.

Subsequent discussions resulted in a far simpler approach:

1) PASID life cycle is from first allocation by a process until that
process exits.
2) All tasks begin with PASID disabled
3) The #GP fault handler tries to fix faulting ENQCMD instructions very
early (thus avoiding complexities of the XSAVE infrastructure)

Change Log:
v4:
- Update commit message in patch #4 (Thomas).
- Update commit message in patch #5 (Thomas).
- Add "Reviewed-by: Thomas Gleixner <tglx@linutronix.de>" in patch #1-#3
and patch #6-#9 (Thomas).
- Rebased to 5.17-rc3.

v3 can be found at https://lore.kernel.org/lkml/20220128202905.2274672-7-fenghua.yu@intel.com/T/#m039e1a201e9894d99b117fa6005bc05724a5a4bb

v3:
- Rename mm_pasid_get() to mm_pasid_set() in patch #5 (Thomas).
- Remove ioasid_get() because it's not used any more when the IOASID
is freed on mm exit in patch #5 (Thomas).
- Remove PASID's refcount exercise in ioasid_put() and rename
ioasid_put() to ioasid_free() in patch #5 and #11 (Thomas).
- Add Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> in patch #10.

v2 can be found at https://lore.kernel.org/lkml/20211217220136.2762116-1-fenghua.yu@intel.com/

v2:
- Free PASID on mm exit instead of in exit(2) or unbind() (Thomas, AndyL,
PeterZ)
- Directly write IA32_PASID MSR in fixup while local IRQ is still disabled
(Thomas)
- Simplify handling ENQCMD in objtool (PeterZ and Josh)
- Define mm_pasid_get(), mm_pasid_drop(), and mm_pasid_init() in mm and
call the functions from IOMMU (Dave Hansen).
- A few changes in the #GP fixup function (Dave Hansen, Tony Luck).
- Initial PASID value is changed to INVALID_PASID (Ashok Raj and
Jacob Pan).
- Add mm_pasid_init(), mm_pasid_get(), and mm_pasid_drop() functions in mm.
So the mm's PASID operations are generic for both X86 and ARM
(Dave Hansen).
- Rename CONFIG_IOMMU_SVA_LIB to more useful and accurate
CONFIG_IOMMU_SVA
- Use CONFIG_IOMMU_SVA for PASID processing condition (Jacob)
- The patch that cleans up old update_pasid() function is in upstream
now (commit: 00ecd5401349 "iommu/vt-d: Clean up unused PASID updating
functions") and therefore it's removed from this version.

v1 can be found at https://lore.kernel.org/lkml/20210920192349.2602141-1-fenghua.yu@intel.com/T/#md6d542091da1d1159eda0a44a16e57d0c0dfb209

Fenghua Yu (10):
iommu/sva: Rename CONFIG_IOMMU_SVA_LIB to CONFIG_IOMMU_SVA
mm: Change CONFIG option for mm->pasid field
iommu/ioasid: Introduce a helper to check for valid PASIDs
kernel/fork: Initialize mm's PASID
iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm
exit
x86/fpu: Clear PASID when copying fpstate
x86/traps: Demand-populate PASID MSR via #GP
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 | 53 ++++++++++++++----
arch/x86/include/asm/disabled-features.h | 7 ++-
arch/x86/kernel/fpu/core.c | 7 +++
arch/x86/kernel/traps.c | 55 +++++++++++++++++++
drivers/iommu/Kconfig | 6 +-
drivers/iommu/Makefile | 2 +-
.../iommu/arm/arm-smmu-v3/arm-smmu-v3-sva.c | 5 +-
drivers/iommu/intel/Kconfig | 2 +-
drivers/iommu/intel/iommu.c | 4 +-
drivers/iommu/intel/svm.c | 9 ---
drivers/iommu/ioasid.c | 39 ++-----------
drivers/iommu/iommu-sva-lib.c | 39 ++++---------
drivers/iommu/iommu-sva-lib.h | 7 +--
include/linux/ioasid.h | 21 +++----
include/linux/mm_types.h | 2 +-
include/linux/sched.h | 3 +
include/linux/sched/mm.h | 26 +++++++++
kernel/fork.c | 15 +++--
mm/init-mm.c | 4 ++
tools/objtool/arch/x86/decode.c | 11 +++-
20 files changed, 197 insertions(+), 120 deletions(-)

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2.35.1