linux.git/arch/x86/kernel/process_64.c, branch v6.5

Merge tag 'iommu-updates-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu

2023-04-30T20:00:38+00:00

Pull iommu updates from Joerg Roedel:

 - Convert to platform remove callback returning void

 - Extend changing default domain to normal group

 - Intel VT-d updates:
     - Remove VT-d virtual command interface and IOASID
     - Allow the VT-d driver to support non-PRI IOPF
     - Remove PASID supervisor request support
     - Various small and misc cleanups

 - ARM SMMU updates:
     - Device-tree binding updates:
         * Allow Qualcomm GPU SMMUs to accept relevant clock properties
         * Document Qualcomm 8550 SoC as implementing an MMU-500
         * Favour new "qcom,smmu-500" binding for Adreno SMMUs

     - Fix S2CR quirk detection on non-architectural Qualcomm SMMU
       implementations

     - Acknowledge SMMUv3 PRI queue overflow when consuming events

     - Document (in a comment) why ATS is disabled for bypass streams

 - AMD IOMMU updates:
     - 5-level page-table support
     - NUMA awareness for memory allocations

 - Unisoc driver: Support for reattaching an existing domain

 - Rockchip driver: Add missing set_platform_dma_ops callback

 - Mediatek driver: Adjust the dma-ranges

 - Various other small fixes and cleanups

* tag 'iommu-updates-v6.4' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu: (82 commits)
  iommu: Remove iommu_group_get_by_id()
  iommu: Make iommu_release_device() static
  iommu/vt-d: Remove BUG_ON in dmar_insert_dev_scope()
  iommu/vt-d: Remove a useless BUG_ON(dev->is_virtfn)
  iommu/vt-d: Remove BUG_ON in map/unmap()
  iommu/vt-d: Remove BUG_ON when domain->pgd is NULL
  iommu/vt-d: Remove BUG_ON in handling iotlb cache invalidation
  iommu/vt-d: Remove BUG_ON on checking valid pfn range
  iommu/vt-d: Make size of operands same in bitwise operations
  iommu/vt-d: Remove PASID supervisor request support
  iommu/vt-d: Use non-privileged mode for all PASIDs
  iommu/vt-d: Remove extern from function prototypes
  iommu/vt-d: Do not use GFP_ATOMIC when not needed
  iommu/vt-d: Remove unnecessary checks in iopf disabling path
  iommu/vt-d: Move PRI handling to IOPF feature path
  iommu/vt-d: Move pfsid and ats_qdep calculation to device probe path
  iommu/vt-d: Move iopf code from SVA to IOPF enabling path
  iommu/vt-d: Allow SVA with device-specific IOPF
  dmaengine: idxd: Add enable/disable device IOPF feature
  arm64: dts: mt8186: Add dma-ranges for the parent "soc" node
  ...

x86/mm/iommu/sva: Do not allow to set FORCE_TAGGED_SVA bit from outside

2023-04-06T20:45:06+00:00

arch_prctl(ARCH_FORCE_TAGGED_SVA) overrides the default and allows LAM
and SVA to co-exist in the process. It is expected by called by the
process when it knows what it is doing.

arch_prctl() operates on the current process, but the same code is
reachable from ptrace where it can be called on arbitrary task.

Make it strict and only allow to set MM_CONTEXT_FORCE_TAGGED_SVA for the
current process.

Fixes: 23e5d9ec2bab ("x86/mm/iommu/sva: Make LAM and SVA mutually exclusive")
Suggested-by: Dmitry Vyukov 
Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Dave Hansen 
Reviewed-by: Dmitry Vyukov 
Link: https://lore.kernel.org/all/20230403111020.3136-3-kirill.shutemov%40linux.intel.com

x86/mm/iommu/sva: Fix error code for LAM enabling failure due to SVA

2023-04-06T20:44:58+00:00

Normally, LAM and SVA are mutually exclusive. LAM enabling will fail if
SVA is already in use.

Correct error code for the failure. EINTR is nonsensical there.

Fixes: 23e5d9ec2bab ("x86/mm/iommu/sva: Make LAM and SVA mutually exclusive")
Reported-by: Dmitry Vyukov 
Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Dave Hansen 
Reviewed-by: Dmitry Vyukov 
Link: https://lore.kernel.org/all/CACT4Y+YfqSMsZArhh25TESmG-U4jO5Hjphz87wKSnTiaw2Wrfw@mail.gmail.com
Link: https://lore.kernel.org/all/20230403111020.3136-2-kirill.shutemov%40linux.intel.com

x86/mm/iommu/sva: Make LAM and SVA mutually exclusive

2023-03-16T20:08:40+00:00

IOMMU and SVA-capable devices know nothing about LAM and only expect
canonical addresses. An attempt to pass down tagged pointer will lead
to address translation failure.

By default do not allow to enable both LAM and use SVA in the same
process.

The new ARCH_FORCE_TAGGED_SVA arch_prctl() overrides the limitation.
By using the arch_prctl() userspace takes responsibility to never pass
tagged address to the device.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Dave Hansen 
Reviewed-by: Ashok Raj 
Reviewed-by: Jacob Pan 
Acked-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/all/20230312112612.31869-12-kirill.shutemov%40linux.intel.com

x86/mm: Provide arch_prctl() interface for LAM

2023-03-16T20:08:39+00:00

Add a few of arch_prctl() handles:

 - ARCH_ENABLE_TAGGED_ADDR enabled LAM. The argument is required number
   of tag bits. It is rounded up to the nearest LAM mode that can
   provide it. For now only LAM_U57 is supported, with 6 tag bits.

 - ARCH_GET_UNTAG_MASK returns untag mask. It can indicates where tag
   bits located in the address.

 - ARCH_GET_MAX_TAG_BITS returns the maximum tag bits user can request.
   Zero if LAM is not supported.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Dave Hansen 
Acked-by: Peter Zijlstra (Intel) 
Tested-by: Alexander Potapenko 
Link: https://lore.kernel.org/all/20230312112612.31869-9-kirill.shutemov%40linux.intel.com

x86: Allow atomic MM_CONTEXT flags setting

2023-03-16T20:08:39+00:00

So far there's no need in atomic setting of MM context flags in
mm_context_t::flags. The flags set early in exec and never change
after that.

LAM enabling requires atomic flag setting. The upcoming flag
MM_CONTEXT_FORCE_TAGGED_SVA can be set much later in the process
lifetime where multiple threads exist.

Convert the field to unsigned long and do MM_CONTEXT_* accesses with
__set_bit() and test_bit().

No functional changes.

Signed-off-by: Kirill A. Shutemov 
Signed-off-by: Dave Hansen 
Acked-by: Peter Zijlstra (Intel) 
Tested-by: Alexander Potapenko 
Link: https://lore.kernel.org/all/20230312112612.31869-3-kirill.shutemov%40linux.intel.com

x86/resctl: fix scheduler confusion with 'current'

2023-03-08T19:48:11+00:00

The implementation of 'current' on x86 is very intentionally special: it
is a very common thing to look up, and it uses 'this_cpu_read_stable()'
to get the current thread pointer efficiently from per-cpu storage.

And the keyword in there is 'stable': the current thread pointer never
changes as far as a single thread is concerned.  Even if when a thread
is preempted, or moved to another CPU, or even across an explicit call
'schedule()' that thread will still have the same value for 'current'.

It is, after all, the kernel base pointer to thread-local storage.
That's why it's stable to begin with, but it's also why it's important
enough that we have that special 'this_cpu_read_stable()' access for it.

So this is all done very intentionally to allow the compiler to treat
'current' as a value that never visibly changes, so that the compiler
can do CSE and combine multiple different 'current' accesses into one.

However, there is obviously one very special situation when the
currently running thread does actually change: inside the scheduler
itself.

So the scheduler code paths are special, and do not have a 'current'
thread at all.  Instead there are _two_ threads: the previous and the
next thread - typically called 'prev' and 'next' (or prev_p/next_p)
internally.

So this is all actually quite straightforward and simple, and not all
that complicated.

Except for when you then have special code that is run in scheduler
context, that code then has to be aware that 'current' isn't really a
valid thing.  Did you mean 'prev'? Did you mean 'next'?

In fact, even if then look at the code, and you use 'current' after the
new value has been assigned to the percpu variable, we have explicitly
told the compiler that 'current' is magical and always stable.  So the
compiler is quite free to use an older (or newer) value of 'current',
and the actual assignment to the percpu storage is not relevant even if
it might look that way.

Which is exactly what happened in the resctl code, that blithely used
'current' in '__resctrl_sched_in()' when it really wanted the new
process state (as implied by the name: we're scheduling 'into' that new
resctl state).  And clang would end up just using the old thread pointer
value at least in some configurations.

This could have happened with gcc too, and purely depends on random
compiler details.  Clang just seems to have been more aggressive about
moving the read of the per-cpu current_task pointer around.

The fix is trivial: just make the resctl code adhere to the scheduler
rules of using the prev/next thread pointer explicitly, instead of using
'current' in a situation where it just wasn't valid.

That same code is then also used outside of the scheduler context (when
a thread resctl state is explicitly changed), and then we will just pass
in 'current' as that pointer, of course.  There is no ambiguity in that
case.

The fix may be trivial, but noticing and figuring out what went wrong
was not.  The credit for that goes to Stephane Eranian.

Reported-by: Stephane Eranian 
Link: https://lore.kernel.org/lkml/20230303231133.1486085-1-eranian@google.com/
Link: https://lore.kernel.org/lkml/alpine.LFD.2.01.0908011214330.3304@localhost.localdomain/
Reviewed-by: Nick Desaulniers 
Tested-by: Tony Luck 
Tested-by: Stephane Eranian 
Tested-by: Babu Moger 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds

Merge tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-12-14T23:03:00+00:00

Pull x86 core updates from Borislav Petkov:

 - Add the call depth tracking mitigation for Retbleed which has been
   long in the making. It is a lighterweight software-only fix for
   Skylake-based cores where enabling IBRS is a big hammer and causes a
   significant performance impact.

   What it basically does is, it aligns all kernel functions to 16 bytes
   boundary and adds a 16-byte padding before the function, objtool
   collects all functions' locations and when the mitigation gets
   applied, it patches a call accounting thunk which is used to track
   the call depth of the stack at any time.

   When that call depth reaches a magical, microarchitecture-specific
   value for the Return Stack Buffer, the code stuffs that RSB and
   avoids its underflow which could otherwise lead to the Intel variant
   of Retbleed.

   This software-only solution brings a lot of the lost performance
   back, as benchmarks suggest:

       https://lore.kernel.org/all/20220915111039.092790446@infradead.org/

   That page above also contains a lot more detailed explanation of the
   whole mechanism

 - Implement a new control flow integrity scheme called FineIBT which is
   based on the software kCFI implementation and uses hardware IBT
   support where present to annotate and track indirect branches using a
   hash to validate them

 - Other misc fixes and cleanups

* tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (80 commits)
  x86/paravirt: Use common macro for creating simple asm paravirt functions
  x86/paravirt: Remove clobber bitmask from .parainstructions
  x86/debug: Include percpu.h in debugreg.h to get DECLARE_PER_CPU() et al
  x86/cpufeatures: Move X86_FEATURE_CALL_DEPTH from bit 18 to bit 19 of word 11, to leave space for WIP X86_FEATURE_SGX_EDECCSSA bit
  x86/Kconfig: Enable kernel IBT by default
  x86,pm: Force out-of-line memcpy()
  objtool: Fix weak hole vs prefix symbol
  objtool: Optimize elf_dirty_reloc_sym()
  x86/cfi: Add boot time hash randomization
  x86/cfi: Boot time selection of CFI scheme
  x86/ibt: Implement FineIBT
  objtool: Add --cfi to generate the .cfi_sites section
  x86: Add prefix symbols for function padding
  objtool: Add option to generate prefix symbols
  objtool: Avoid O(bloody terrible) behaviour -- an ode to libelf
  objtool: Slice up elf_create_section_symbol()
  kallsyms: Revert "Take callthunks into account"
  x86: Unconfuse CONFIG_ and X86_FEATURE_ namespaces
  x86/retpoline: Fix crash printing warning
  x86/paravirt: Fix a !PARAVIRT build warning
  ...

x86/cpu: Switch to cpu_feature_enabled() for X86_FEATURE_XENPV

2022-11-22T15:18:19+00:00

Convert the remaining cases of static_cpu_has(X86_FEATURE_XENPV) and
boot_cpu_has(X86_FEATURE_XENPV) to use cpu_feature_enabled(), allowing
more efficient code in case the kernel is configured without
CONFIG_XEN_PV.

Signed-off-by: Juergen Gross 
Signed-off-by: Borislav Petkov 
Acked-by: Dave Hansen 
Link: https://lore.kernel.org/r/20221104072701.20283-6-jgross@suse.com

x86/percpu: Move irq_stack variables next to current_task

2022-10-17T14:41:05+00:00

Further extend struct pcpu_hot with the hard and soft irq stack
pointers.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20220915111145.599170752@infradead.org