A typo caused the interrupt handler to branch immediately to the
common "unknown interrupt" handler and skip the special case test for
denormal cause.
This does not affect KVM softpatch handling (e.g., for POWER9 TM
assist) because the KVM test was moved to common code by commit
9600f261ac ("powerpc/64s/exception: Move KVM test to common code")
just before this bug was introduced.
Fixes: 3f7fbd97d0 ("powerpc/64s/exception: Clean up SRR specifiers")
Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Tested-by: Paul Menzel <pmenzel@molgen.mpg.de>
[mpe: Split selftest into a separate patch]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200708074942.1713396-1-npiggin@gmail.com
The method struct pci_error_handlers.error_detected() is defined and
documented as taking an 'enum pci_channel_state' for the second argument,
but most drivers use 'pci_channel_state_t' instead.
This 'pci_channel_state_t' is not a typedef for the enum but a typedef for
a bitwise type in order to have better/stricter typechecking.
Consolidate everything by using 'pci_channel_state_t' in the method's
definition, in the related helpers and in the drivers.
Enforce use of 'pci_channel_state_t' by replacing 'enum pci_channel_state'
with an anonymous 'enum'.
Note: Currently, from a typechecking point of view this patch changes
nothing because only the constants defined by the enum are bitwise, not the
enum itself (sparse doesn't have the notion of 'bitwise enum'). This may
change in some not too far future, hence the patch.
[bhelgaas: squash in
https://lore.kernel.org/r/20200702162651.49526-3-luc.vanoostenryck@gmail.comhttps://lore.kernel.org/r/20200702162651.49526-4-luc.vanoostenryck@gmail.com]
Link: https://lore.kernel.org/r/20200702162651.49526-2-luc.vanoostenryck@gmail.com
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Some Makefiles already pass -fno-stack-protector unconditionally.
For example, arch/arm64/kernel/vdso/Makefile, arch/x86/xen/Makefile.
No problem report so far about hard-coding this option. So, we can
assume all supported compilers know -fno-stack-protector.
GCC 4.8 and Clang support this option (https://godbolt.org/z/_HDGzN)
Get rid of cc-option from -fno-stack-protector.
Remove CONFIG_CC_HAS_STACKPROTECTOR_NONE, which is always 'y'.
Note:
arch/mips/vdso/Makefile adds -fno-stack-protector twice, first
unconditionally, and second conditionally. I removed the second one.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Pull powerpc fixes from Michael Ellerman:
- One fix for the interrupt rework we did last release which broke
KVM-PR
- Three commits fixing some fallout from the READ_ONCE() changes
interacting badly with our 8xx 16K pages support, which uses a pte_t
that is a structure of 4 actual PTEs
- A cleanup of the 8xx pte_update() to use the newly added pmd_off()
- A fix for a crash when handling an oops if CONFIG_DEBUG_VIRTUAL is
enabled
- A minor fix for the SPU syscall generation
Thanks to Aneesh Kumar K.V, Christian Zigotzky, Christophe Leroy, Mike
Rapoport, Nicholas Piggin.
* tag 'powerpc-5.8-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/8xx: Provide ptep_get() with 16k pages
mm: Allow arches to provide ptep_get()
mm/gup: Use huge_ptep_get() in gup_hugepte()
powerpc/syscalls: Use the number when building SPU syscall table
powerpc/8xx: use pmd_off() to access a PMD entry in pte_update()
powerpc/64s: Fix KVM interrupt using wrong save area
powerpc: Fix kernel crash in show_instructions() w/DEBUG_VIRTUAL
Now that we've renamed probe_kernel_address() to get_kernel_nofault()
and made it look and behave more in line with get_user(), some of the
subtle type behavior differences end up being more obvious and possibly
dangerous.
When you do
get_user(val, user_ptr);
the type of the access comes from the "user_ptr" part, and the above
basically acts as
val = *user_ptr;
by design (except, of course, for the fact that the actual dereference
is done with a user access).
Note how in the above case, the type of the end result comes from the
pointer argument, and then the value is cast to the type of 'val' as
part of the assignment.
So the type of the pointer is ultimately the more important type both
for the access itself.
But 'get_kernel_nofault()' may now _look_ similar, but it behaves very
differently. When you do
get_kernel_nofault(val, kernel_ptr);
it behaves like
val = *(typeof(val) *)kernel_ptr;
except, of course, for the fact that the actual dereference is done with
exception handling so that a faulting access is suppressed and returned
as the error code.
But note how different the casting behavior of the two superficially
similar accesses are: one does the actual access in the size of the type
the pointer points to, while the other does the access in the size of
the target, and ignores the pointer type entirely.
Actually changing get_kernel_nofault() to act like get_user() is almost
certainly the right thing to do eventually, but in the meantime this
patch adds logit to at least verify that the pointer type is compatible
with the type of the result.
In many cases, this involves just casting the pointer to 'void *' to
make it obvious that the type of the pointer is not the important part.
It's not how 'get_user()' acts, but at least the behavioral difference
is now obvious and explicit.
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Better describe what this helper does, and match the naming of
copy_from_kernel_nofault.
Also switch the argument order around, so that it acts and looks
like get_user().
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With CONFIG_DEBUG_VIRTUAL=y, we can hit a BUG() if we take a hard
lockup watchdog interrupt when in OPAL mode.
This happens in show_instructions() if the kernel takes the watchdog
NMI IPI, or any other interrupt, with MSR_IR == 0. show_instructions()
updates the variable pc in the loop and the second iteration will
result in BUG().
We hit the BUG_ON due the below check in __va()
#define __va(x)
({
VIRTUAL_BUG_ON((unsigned long)(x) >= PAGE_OFFSET);
(void *)(unsigned long)((phys_addr_t)(x) | PAGE_OFFSET);
})
Fix it by moving the check out of the loop. Also update nip so that
the nip == pc check still matches.
Fixes: 4dd7554a64 ("powerpc/64: Add VIRTUAL_BUG_ON checks for __va and __pa addresses")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
[mpe: Use IS_ENABLED(), massage change log]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200524093822.423487-1-aneesh.kumar@linux.ibm.com
Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on a platform or
user).
Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages. And in
result it not only may print unwanted messages from other CPUs, but also
omit printing at all in the unlucky case where the printk() was deferred.
Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems an easier
approach than introducing more printk buffers. Also, it will consolidate
printings with headers.
Introduce show_stack_loglvl(), that eventually will substitute
show_stack().
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@arista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Link: http://lkml.kernel.org/r/20200418201944.482088-27-dima@arista.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull powerpc updates from Michael Ellerman:
- Support for userspace to send requests directly to the on-chip GZIP
accelerator on Power9.
- Rework of our lockless page table walking (__find_linux_pte()) to
make it safe against parallel page table manipulations without
relying on an IPI for serialisation.
- A series of fixes & enhancements to make our machine check handling
more robust.
- Lots of plumbing to add support for "prefixed" (64-bit) instructions
on Power10.
- Support for using huge pages for the linear mapping on 8xx (32-bit).
- Remove obsolete Xilinx PPC405/PPC440 support, and an associated sound
driver.
- Removal of some obsolete 40x platforms and associated cruft.
- Initial support for booting on Power10.
- Lots of other small features, cleanups & fixes.
Thanks to: Alexey Kardashevskiy, Alistair Popple, Andrew Donnellan,
Andrey Abramov, Aneesh Kumar K.V, Balamuruhan S, Bharata B Rao, Bulent
Abali, Cédric Le Goater, Chen Zhou, Christian Zigotzky, Christophe
JAILLET, Christophe Leroy, Dmitry Torokhov, Emmanuel Nicolet, Erhard F.,
Gautham R. Shenoy, Geoff Levand, George Spelvin, Greg Kurz, Gustavo A.
R. Silva, Gustavo Walbon, Haren Myneni, Hari Bathini, Joel Stanley,
Jordan Niethe, Kajol Jain, Kees Cook, Leonardo Bras, Madhavan
Srinivasan., Mahesh Salgaonkar, Markus Elfring, Michael Neuling, Michal
Simek, Nathan Chancellor, Nathan Lynch, Naveen N. Rao, Nicholas Piggin,
Oliver O'Halloran, Paul Mackerras, Pingfan Liu, Qian Cai, Ram Pai,
Raphael Moreira Zinsly, Ravi Bangoria, Sam Bobroff, Sandipan Das, Segher
Boessenkool, Stephen Rothwell, Sukadev Bhattiprolu, Tyrel Datwyler,
Wolfram Sang, Xiongfeng Wang.
* tag 'powerpc-5.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (299 commits)
powerpc/pseries: Make vio and ibmebus initcalls pseries specific
cxl: Remove dead Kconfig options
powerpc: Add POWER10 architected mode
powerpc/dt_cpu_ftrs: Add MMA feature
powerpc/dt_cpu_ftrs: Enable Prefixed Instructions
powerpc/dt_cpu_ftrs: Advertise support for ISA v3.1 if selected
powerpc: Add support for ISA v3.1
powerpc: Add new HWCAP bits
powerpc/64s: Don't set FSCR bits in INIT_THREAD
powerpc/64s: Save FSCR to init_task.thread.fscr after feature init
powerpc/64s: Don't let DT CPU features set FSCR_DSCR
powerpc/64s: Don't init FSCR_DSCR in __init_FSCR()
powerpc/32s: Fix another build failure with CONFIG_PPC_KUAP_DEBUG
powerpc/module_64: Use special stub for _mcount() with -mprofile-kernel
powerpc/module_64: Simplify check for -mprofile-kernel ftrace relocations
powerpc/module_64: Consolidate ftrace code
powerpc/32: Disable KASAN with pages bigger than 16k
powerpc/uaccess: Don't set KUEP by default on book3s/32
powerpc/uaccess: Don't set KUAP by default on book3s/32
powerpc/8xx: Reduce time spent in allow_user_access() and friends
...
Merge updates from Andrew Morton:
"A few little subsystems and a start of a lot of MM patches.
Subsystems affected by this patch series: squashfs, ocfs2, parisc,
vfs. With mm subsystems: slab-generic, slub, debug, pagecache, gup,
swap, memcg, pagemap, memory-failure, vmalloc, kasan"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (128 commits)
kasan: move kasan_report() into report.c
mm/mm_init.c: report kasan-tag information stored in page->flags
ubsan: entirely disable alignment checks under UBSAN_TRAP
kasan: fix clang compilation warning due to stack protector
x86/mm: remove vmalloc faulting
mm: remove vmalloc_sync_(un)mappings()
x86/mm/32: implement arch_sync_kernel_mappings()
x86/mm/64: implement arch_sync_kernel_mappings()
mm/ioremap: track which page-table levels were modified
mm/vmalloc: track which page-table levels were modified
mm: add functions to track page directory modifications
s390: use __vmalloc_node in stack_alloc
powerpc: use __vmalloc_node in alloc_vm_stack
arm64: use __vmalloc_node in arch_alloc_vmap_stack
mm: remove vmalloc_user_node_flags
mm: switch the test_vmalloc module to use __vmalloc_node
mm: remove __vmalloc_node_flags_caller
mm: remove both instances of __vmalloc_node_flags
mm: remove the prot argument to __vmalloc_node
mm: remove the pgprot argument to __vmalloc
...
PVR value of 0x0F000006 means we are arch v3.1 compliant (i.e.
POWER10). This is used by phyp and kvm when booting as a pseries guest
to detect the presence of new P10 features and to enable the
appropriate hwcap and facility bits.
Signed-off-by: Alistair Popple <alistair@popple.id.au>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
[mpe: Fall through to __init_FSCR rather than duplicating it, drop
hack to set current->thread.fscr now that is handled elsewhere.]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200521014341.29095-8-alistair@popple.id.au
At boot the FSCR is initialised via one of two paths. On most systems
it's set to a hard coded value in __init_FSCR().
On newer skiboot systems we use the device tree CPU features binding,
where firmware can tell Linux what bits to set in FSCR (and HFSCR).
In both cases the value that's configured at boot is not propagated
into the init_task.thread.fscr value prior to the initial fork of init
(pid 1), which means the value is not used by any processes other than
swapper (the idle task).
For the __init_FSCR() case this is OK, because the value in
init_task.thread.fscr is initialised to something sensible. However it
does mean that the value set in __init_FSCR() is not used other than
for swapper, which is odd and confusing.
The bigger problem is for the device tree CPU features case it
prevents firmware from setting (or clearing) FSCR bits for use by user
space. This means all existing kernels can not have features
enabled/disabled by firmware if those features require
setting/clearing FSCR bits.
We can handle both cases by saving the FSCR value into
init_task.thread.fscr after we have initialised it at boot. This fixes
the bug for device tree CPU features, and will allow us to simplify
the initialisation for the __init_FSCR() case in a future patch.
Fixes: 5a61ef74f2 ("powerpc/64s: Support new device tree binding for discovering CPU features")
Cc: stable@vger.kernel.org # v4.12+
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200527145843.2761782-3-mpe@ellerman.id.au
The device tree CPU features binding includes FSCR bit numbers which
Linux is instructed to set by firmware.
Whether that's a good idea or not, in the case of the DSCR the Linux
implementation has a hard requirement that the FSCR_DSCR bit not be
set by default. We use it to track when a process reads/writes to
DSCR, so it must be clear to begin with.
So if firmware tells us to set FSCR_DSCR we must ignore it.
Currently this does not cause a bug in our DSCR handling because the
value of FSCR that the device tree CPU features code establishes is
only used by swapper. All other tasks use the value hard coded in
init_task.thread.fscr.
However we'd like to fix that in a future commit, at which point this
will become necessary.
Fixes: 5a61ef74f2 ("powerpc/64s: Support new device tree binding for discovering CPU features")
Cc: stable@vger.kernel.org # v4.12+
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200527145843.2761782-2-mpe@ellerman.id.au
__init_FSCR() was added originally in commit 2468dcf641 ("powerpc:
Add support for context switching the TAR register") (Feb 2013), and
only set FSCR_TAR.
At that point FSCR (Facility Status and Control Register) was not
context switched, so the setting was permanent after boot.
Later we added initialisation of FSCR_DSCR to __init_FSCR(), in commit
54c9b2253d ("powerpc: Set DSCR bit in FSCR setup") (Mar 2013), again
that was permanent after boot.
Then commit 2517617e0d ("powerpc: Fix context switch DSCR on
POWER8") (Aug 2013) added a limited context switch of FSCR, just the
FSCR_DSCR bit was context switched based on thread.dscr_inherit. That
commit said "This clears the H/FSCR DSCR bit initially", but it
didn't, it left the initialisation of FSCR_DSCR in __init_FSCR().
However the initial context switch from init_task to pid 1 would clear
FSCR_DSCR because thread.dscr_inherit was 0.
That commit also introduced the requirement that FSCR_DSCR be clear
for user processes, so that we can take the facility unavailable
interrupt in order to manage dscr_inherit.
Then in commit 152d523e63 ("powerpc: Create context switch helpers
save_sprs() and restore_sprs()") (Dec 2015) FSCR was added to
thread_struct. However it still wasn't fully context switched, we just
took the existing value and set FSCR_DSCR if the new thread had
dscr_inherit set. FSCR was still initialised at boot to FSCR_DSCR |
FSCR_TAR, but that value was not propagated into the thread_struct, so
the initial context switch set FSCR_DSCR back to 0.
Finally commit b57bd2de8c ("powerpc: Improve FSCR init and context
switching") (Jun 2016) added a full context switch of the FSCR, and
added an initialisation of init_task.thread.fscr to FSCR_TAR |
FSCR_EBB, but omitted FSCR_DSCR.
The end result is that swapper runs with FSCR_DSCR set because of the
initialisation in __init_FSCR(), but no other processes do, they use
the value from init_task.thread.fscr.
Having FSCR_DSCR set for swapper allows it to access SPR 3 from
userspace, but swapper never runs userspace, so it has no useful
effect. It's also confusing to have the value initialised in two
places to two different values.
So remove FSCR_DSCR from __init_FSCR(), this at least gets us to the
point where there's a single value of FSCR, even if it's still set in
two places.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Tested-by: Alistair Popple <alistair@popple.id.au>
Link: https://lore.kernel.org/r/20200527145843.2761782-1-mpe@ellerman.id.au
Since commit c55d7b5e64 ("powerpc: Remove STRICT_KERNEL_RWX
incompatibility with RELOCATABLE"), powerpc kernels with
-mprofile-kernel can crash in certain scenarios with a trace like below:
BUG: Unable to handle kernel instruction fetch (NULL pointer?)
Faulting instruction address: 0x00000000
Oops: Kernel access of bad area, sig: 11 [#1]
LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=256 DEBUG_PAGEALLOC NUMA PowerNV
<snip>
NIP [0000000000000000] 0x0
LR [c0080000102c0048] ext4_iomap_end+0x8/0x30 [ext4]
Call Trace:
iomap_apply+0x20c/0x920 (unreliable)
iomap_bmap+0xfc/0x160
ext4_bmap+0xa4/0x180 [ext4]
bmap+0x4c/0x80
jbd2_journal_init_inode+0x44/0x1a0 [jbd2]
ext4_load_journal+0x440/0x860 [ext4]
ext4_fill_super+0x342c/0x3ab0 [ext4]
mount_bdev+0x25c/0x290
ext4_mount+0x28/0x50 [ext4]
legacy_get_tree+0x4c/0xb0
vfs_get_tree+0x4c/0x130
do_mount+0xa18/0xc50
sys_mount+0x158/0x180
system_call+0x5c/0x68
The NIP points to NULL, or a random location (data even), while the LR
always points to the LEP of a function (with an offset of 8), indicating
that something went wrong with ftrace. However, ftrace is not
necessarily active when such crashes occur.
The kernel OOPS sometimes follows a warning from ftrace indicating that
some module functions could not be patched with a nop. Other times, if a
module is loaded early during boot, instruction patching can fail due to
a separate bug, but the error is not reported due to missing error
reporting.
In all the above cases when instruction patching fails, ftrace will be
disabled but certain kernel module functions will be left with default
calls to _mcount(). This is not a problem with ELFv1. However, with
-mprofile-kernel, the default stub is problematic since it depends on a
valid module TOC in r2. If the kernel (or a different module) calls into
a function that does not use the TOC, the function won't have a prologue
to setup the module TOC. When that function calls into _mcount(), we
will end up in the relocation stub that will use the previous TOC, and
end up trying to jump into a random location. From the above trace:
iomap_apply+0x20c/0x920 [kernel TOC]
|
V
ext4_iomap_end+0x8/0x30 [no GEP == kernel TOC]
|
V
_mcount() stub
[uses kernel TOC -> random entry]
To address this, let's change over to using the special stub that is
used for ftrace_[regs_]caller() for _mcount(). This ensures that we are
not dependent on a valid module TOC in r2 for default _mcount()
handling.
Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Tested-by: Qian Cai <cai@lca.pw>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/8affd4298d22099bbd82544fab8185700a6222b1.1587488954.git.naveen.n.rao@linux.vnet.ibm.com
For -mprofile-kernel, we need special handling when generating stubs for
ftrace calls such as _mcount(). To faciliate this, we check if a
R_PPC64_REL24 relocation is for a symbol named "_mcount()" along with
also checking the instruction sequence. The latter is not really
required since "_mcount()" is an exported symbol and kernel modules
cannot use it. As such, drop the additional checking and simplify the
code. This helps unify stub creation for ftrace stubs with
-mprofile-kernel and aids in code reuse.
Also rename is_mprofile_mcount_callsite() to is_mprofile_ftrace_call()
to reflect the checking being done.
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7d9c316adfa1fb787ad268bb4691e7e4059ff2d5.1587488954.git.naveen.n.rao@linux.vnet.ibm.com
Implement rtas_call_reentrant() for reentrant rtas-calls:
"ibm,int-on", "ibm,int-off",ibm,get-xive" and "ibm,set-xive".
On LoPAPR Version 1.1 (March 24, 2016), from 7.3.10.1 to 7.3.10.4,
items 2 and 3 say:
2 - For the PowerPC External Interrupt option: The * call must be
reentrant to the number of processors on the platform.
3 - For the PowerPC External Interrupt option: The * argument call
buffer for each simultaneous call must be physically unique.
So, these rtas-calls can be called in a lockless way, if using
a different buffer for each cpu doing such rtas call.
For this, it was suggested to add the buffer (struct rtas_args)
in the PACA struct, so each cpu can have it's own buffer.
The PACA struct received a pointer to rtas buffer, which is
allocated in the memory range available to rtas 32-bit.
Reentrant rtas calls are useful to avoid deadlocks in crashing,
where rtas-calls are needed, but some other thread crashed holding
the rtas.lock.
This is a backtrace of a deadlock from a kdump testing environment:
#0 arch_spin_lock
#1 lock_rtas ()
#2 rtas_call (token=8204, nargs=1, nret=1, outputs=0x0)
#3 ics_rtas_mask_real_irq (hw_irq=4100)
#4 machine_kexec_mask_interrupts
#5 default_machine_crash_shutdown
#6 machine_crash_shutdown
#7 __crash_kexec
#8 crash_kexec
#9 oops_end
Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
[mpe: Move under #ifdef PSERIES to avoid build breakage]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200518234245.200672-3-leobras.c@gmail.com
While providing guests, it's desirable to resize it's memory on demand.
By now, it's possible to do so by creating a guest with a small base
memory, hot-plugging all the rest, and using 'movable_node' kernel
command-line parameter, which puts all hot-plugged memory in
ZONE_MOVABLE, allowing it to be removed whenever needed.
But there is an issue regarding guest reboot:
If memory is hot-plugged, and then the guest is rebooted, all hot-plugged
memory goes to ZONE_NORMAL, which offers no guaranteed hot-removal.
It usually prevents this memory to be hot-removed from the guest.
It's possible to use device-tree information to fix that behavior, as
it stores flags for LMB ranges on ibm,dynamic-memory-vN.
It involves marking each memblock with the correct flags as hotpluggable
memory, which mm/memblock.c puts in ZONE_MOVABLE during boot if
'movable_node' is passed.
For carrying such information, the new flag DRCONF_MEM_HOTREMOVABLE was
proposed and accepted into Power Architecture documentation.
This flag should be:
- true (b=1) if the hypervisor may want to hot-remove it later, and
- false (b=0) if it does not care.
During boot, guest kernel reads the device-tree, early_init_drmem_lmb()
is called for every added LMBs. Here, checking for this new flag and
marking memblocks as hotplugable memory is enough to get the desirable
behavior.
This should cause no change if 'movable_node' parameter is not passed
in kernel command-line.
Signed-off-by: Leonardo Bras <leonardo@linux.ibm.com>
Reviewed-by: Bharata B Rao <bharata@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200402195156.626430-1-leonardo@linux.ibm.com
Currently when we boot on a big core system, we get this print:
[ 0.040500] Using small cores at SMT level
This is misleading as we've actually detected big cores.
This patch clears up the print to say we've detect big cores but are
using small cores for scheduling.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200528230731.1235752-1-mikey@neuling.org
Pull vfs updates from Al Viro:
"Assorted patches from Miklos.
An interesting part here is /proc/mounts stuff..."
The "/proc/mounts stuff" is using a cursor for keeeping the location
data while traversing the mount listing.
Also probably worth noting is the addition of faccessat2(), which takes
an additional set of flags to specify how the lookup is done
(AT_EACCESS, AT_SYMLINK_NOFOLLOW, AT_EMPTY_PATH).
* 'from-miklos' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
vfs: add faccessat2 syscall
vfs: don't parse "silent" option
vfs: don't parse "posixacl" option
vfs: don't parse forbidden flags
statx: add mount_root
statx: add mount ID
statx: don't clear STATX_ATIME on SB_RDONLY
uapi: deprecate STATX_ALL
utimensat: AT_EMPTY_PATH support
vfs: split out access_override_creds()
proc/mounts: add cursor
aio: fix async fsync creds
vfs: allow unprivileged whiteout creation
