KVM/ARM Fixes for v4.12-rc5 - Take 2

Changes include:
 - Fix an issue with migrating GICv2 VMs on GICv3 systems.
 - Squashed a bug for gicv3 when figuring out preemption levels.
 - Fix a potential null pointer derefence in KVM happening under memory
   pressure.
 - Maintain RES1 bits in the SCTLR_EL2 to make sure KVM works on new
   architecture revisions.
 - Allow unaligned accesses at EL2/HYP

__do_hyp_init has the rather bad habit of ignoring RES1 bits and
writing them back as zero. On a v8.0-8.2 CPU, this doesn't do anything
bad, but may end-up being pretty nasty on future revisions of the
architecture.

Let's preserve those bits so that we don't have to fix this later on.

Cc: stable@vger.kernel.org
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>

The BAD_MADT_GICC_ENTRY() macro checks if a GICC MADT entry passes
muster from an ACPI specification standpoint. Current macro detects the
MADT GICC entry length through ACPI firmware version (it changed from 76
to 80 bytes in the transition from ACPI 5.1 to ACPI 6.0 specification)
but always uses (erroneously) the ACPICA (latest) struct (ie struct
acpi_madt_generic_interrupt - that is 80-bytes long) length to check if
the current GICC entry memory record exceeds the MADT table end in
memory as defined by the MADT table header itself, which may result in
false negatives depending on the ACPI firmware version and how the MADT
entries are laid out in memory (ie on ACPI 5.1 firmware MADT GICC
entries are 76 bytes long, so by adding 80 to a GICC entry start address
in memory the resulting address may well be past the actual MADT end,
triggering a false negative).

Fix the BAD_MADT_GICC_ENTRY() macro by reshuffling the condition checks
and update them to always use the firmware version specific MADT GICC
entry length in order to carry out boundary checks.

Fixes: b6cfb277378e ("ACPI / ARM64: add BAD_MADT_GICC_ENTRY() macro")
Reported-by: Julien Grall <julien.grall@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Julien Grall <julien.grall@arm.com>
Cc: Hanjun Guo <hanjun.guo@linaro.org>
Cc: Al Stone <ahs3@redhat.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Currently, cpus_set_cap() calls static_branch_enable_cpuslocked(), which
must take the jump_label mutex.

We call cpus_set_cap() in the secondary bringup path, from the idle
thread where interrupts are disabled. Taking a mutex in this path "is a
NONO" regardless of whether it's contended, and something we must avoid.
We didn't spot this until recently, as ___might_sleep() won't warn for
this case until all CPUs have been brought up.

This patch avoids taking the mutex in the secondary bringup path. The
poking of static keys is deferred until enable_cpu_capabilities(), which
runs in a suitable context on the boot CPU. To account for the static
keys being set later, cpus_have_const_cap() is updated to use another
static key to check whether the const cap keys have been initialised,
falling back to the caps bitmap until this is the case.

This means that users of cpus_have_const_cap() gain should only gain a
single additional NOP in the fast path once the const caps are
initialised, but should always see the current cap value.

The hyp code should never dereference the caps array, since the caps are
initialized before we run the module initcall to initialise hyp. A check
is added to the hyp init code to document this requirement.

This change will sidestep a number of issues when the upcoming hotplug
locking rework is merged.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Marc Zyniger <marc.zyngier@arm.com>
Reviewed-by: Suzuki Poulose <suzuki.poulose@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Sewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

The cmpxchg implementation introduced by commit c342f78217e8 ("arm64:
cmpxchg: patch in lse instructions when supported by the CPU") performs
an apparently redundant register move of [old] to [oldval] in the
success case - it always uses the same register width as [oldval] was
originally loaded with, and is only executed when [old] and [oldval] are
known to be equal anyway.

The only effect it seemingly does have is to take up a surprising amount
of space in the kernel text, as removing it reveals:

   text	   data	    bss	    dec	    hex	filename
12426658	1348614	4499749	18275021	116dacd	vmlinux.o.new
12429238	1348614	4499749	18277601	116e4e1	vmlinux.o.old

Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Pull more arm64 updates from Catalin Marinas:

 - Silence module allocation failures when CONFIG_ARM*_MODULE_PLTS is
   enabled. This requires a check for __GFP_NOWARN in alloc_vmap_area()

 - Improve/sanitise user tagged pointers handling in the kernel

 - Inline asm fixes/cleanups

* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: Silence first allocation with CONFIG_ARM64_MODULE_PLTS=y
  ARM: Silence first allocation with CONFIG_ARM_MODULE_PLTS=y
  mm: Silence vmap() allocation failures based on caller gfp_flags
  arm64: uaccess: suppress spurious clang warning
  arm64: atomic_lse: match asm register sizes
  arm64: armv8_deprecated: ensure extension of addr
  arm64: uaccess: ensure extension of access_ok() addr
  arm64: ensure extension of smp_store_release value
  arm64: xchg: hazard against entire exchange variable
  arm64: documentation: document tagged pointer stack constraints
  arm64: entry: improve data abort handling of tagged pointers
  arm64: hw_breakpoint: fix watchpoint matching for tagged pointers
  arm64: traps: fix userspace cache maintenance emulation on a tagged pointer

Pull Kbuild UAPI updates from Masahiro Yamada:
 "Improvement of headers_install by Nicolas Dichtel.

  It has been long since the introduction of uapi directories, but the
  de-coupling of exported headers has not been completed. Headers listed
  in header-y are exported whether they exist in uapi directories or
  not. His work fixes this inconsistency.

  All (and only) headers under uapi directories are now exported. The
  asm-generic wrappers are still exceptions, but this is a big step
  forward"

* tag 'kbuild-uapi-v4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  arch/include: remove empty Kbuild files
  uapi: export all arch specifics directories
  uapi: export all headers under uapi directories
  smc_diag.h: fix include from userland
  btrfs_tree.h: fix include from userland
  uapi: includes linux/types.h before exporting files
  Makefile.headersinst: remove destination-y option
  Makefile.headersinst: cleanup input files
  x86: stop exporting msr-index.h to userland
  nios2: put setup.h in uapi
  h8300: put bitsperlong.h in uapi

Regularly, when a new header is created in include/uapi/, the developer
forgets to add it in the corresponding Kbuild file. This error is usually
detected after the release is out.

In fact, all headers under uapi directories should be exported, thus it's
useless to have an exhaustive list.

After this patch, the following files, which were not exported, are now
exported (with make headers_install_all):
asm-arc/kvm_para.h
asm-arc/ucontext.h
asm-blackfin/shmparam.h
asm-blackfin/ucontext.h
asm-c6x/shmparam.h
asm-c6x/ucontext.h
asm-cris/kvm_para.h
asm-h8300/shmparam.h
asm-h8300/ucontext.h
asm-hexagon/shmparam.h
asm-m32r/kvm_para.h
asm-m68k/kvm_para.h
asm-m68k/shmparam.h
asm-metag/kvm_para.h
asm-metag/shmparam.h
asm-metag/ucontext.h
asm-mips/hwcap.h
asm-mips/reg.h
asm-mips/ucontext.h
asm-nios2/kvm_para.h
asm-nios2/ucontext.h
asm-openrisc/shmparam.h
asm-parisc/kvm_para.h
asm-powerpc/perf_regs.h
asm-sh/kvm_para.h
asm-sh/ucontext.h
asm-tile/shmparam.h
asm-unicore32/shmparam.h
asm-unicore32/ucontext.h
asm-x86/hwcap2.h
asm-xtensa/kvm_para.h
drm/armada_drm.h
drm/etnaviv_drm.h
drm/vgem_drm.h
linux/aspeed-lpc-ctrl.h
linux/auto_dev-ioctl.h
linux/bcache.h
linux/btrfs_tree.h
linux/can/vxcan.h
linux/cifs/cifs_mount.h
linux/coresight-stm.h
linux/cryptouser.h
linux/fsmap.h
linux/genwqe/genwqe_card.h
linux/hash_info.h
linux/kcm.h
linux/kcov.h
linux/kfd_ioctl.h
linux/lightnvm.h
linux/module.h
linux/nbd-netlink.h
linux/nilfs2_api.h
linux/nilfs2_ondisk.h
linux/nsfs.h
linux/pr.h
linux/qrtr.h
linux/rpmsg.h
linux/sched/types.h
linux/sed-opal.h
linux/smc.h
linux/smc_diag.h
linux/stm.h
linux/switchtec_ioctl.h
linux/vfio_ccw.h
linux/wil6210_uapi.h
rdma/bnxt_re-abi.h

Note that I have removed from this list the files which are generated in every
exported directories (like .install or .install.cmd).

Thanks to Julien Floret <julien.floret@6wind.com> for the tip to get all
subdirs with a pure makefile command.

For the record, note that exported files for asm directories are a mix of
files listed by:
 - include/uapi/asm-generic/Kbuild.asm;
 - arch/<arch>/include/uapi/asm/Kbuild;
 - arch/<arch>/include/asm/Kbuild.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Mark Salter <msalter@redhat.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Clang tries to warn when there's a mismatch between an operand's size,
and the size of the register it is held in, as this may indicate a bug.
Specifically, clang warns when the operand's type is less than 64 bits
wide, and the register is used unqualified (i.e. %N rather than %xN or
%wN).

Unfortunately clang can generate these warnings for unreachable code.
For example, for code like:

do {                                            \
        typeof(*(ptr)) __v = (v);               \
        switch(sizeof(*(ptr))) {                \
        case 1:                                 \
                // assume __v is 1 byte wide    \
                asm ("{op}b %w0" : : "r" (v));  \
                break;                          \
        case 8:                                 \
                // assume __v is 8 bytes wide   \
                asm ("{op} %0" : : "r" (v));    \
                break;                          \
        }
while (0)

... if op() were passed a char value and pointer to char, clang may
produce a warning for the unreachable case where sizeof(*(ptr)) is 8.

For the same reasons, clang produces warnings when __put_user_err() is
used for types that are less than 64 bits wide.

We could avoid this with a cast to a fixed-width type in each of the
cases. However, GCC will then warn that pointer types are being cast to
mismatched integer sizes (in unreachable paths).

Another option would be to use the same union trickery as we do for
__smp_store_release() and __smp_load_acquire(), but this is fairly
invasive.

Instead, this patch suppresses the clang warning by using an x modifier
in the assembly for the 8 byte case of __put_user_err(). No additional
work is necessary as the value has been cast to typeof(*(ptr)), so the
compiler will have performed any necessary extension for the reachable
case.

For consistency, __get_user_err() is also updated to use the x modifier
for its 8 byte case.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

The LSE atomic code uses asm register variables to ensure that
parameters are allocated in specific registers. In the majority of cases
we specifically ask for an x register when using 64-bit values, but in a
couple of cases we use a w regsiter for a 64-bit value.

For asm register variables, the compiler only cares about the register
index, with wN and xN having the same meaning. The compiler determines
the register size to use based on the type of the variable. Thus, this
inconsistency is merely confusing, and not harmful to code generation.

For consistency, this patch updates those cases to use the x register
alias. There should be no functional change as a result of this patch.

Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>