Before, the code to do RDTSC looked like:
rdtsc
shl $0x20, %rdx
mov %eax, %eax
or %rdx, %rax
The "mov %eax, %eax" is required to clear the high 32 bits of RAX.
By declaring low and high as 64-bit variables, the code is
simplified to:
rdtsc
shl $0x20,%rdx
or %rdx,%rax
Yes, it's a 2-byte instruction that's not on a critical path,
but there are principles to be upheld.
Every user of EAX_EDX_RET has been checked. I tried to check
users of EAX_EDX_ARGS, but there weren't any, so I deleted it to
be safe.
( There's no benefit to making "high" 64 bits, but it was the
simplest way to proceed. )
Signed-off-by: George Spelvin <linux@horizon.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: jacob.jun.pan@linux.intel.com
Link: http://lkml.kernel.org/r/20150618075906.4615.qmail@ns.horizon.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
rdtsc_barrier(); rdtsc() is an unnecessary mouthful and requires
more thought than should be necessary. Add an rdtsc_ordered()
helper and replace the trivial call sites with it.
This should not change generated code. The duplication of the
fence asm is temporary.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/dddbf98a2af53312e9aa73a5a2b1622fe5d6f52b.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Now that there is no paravirt TSC, the "native" is
inappropriate. The function does RDTSC, so give it the obvious
name: rdtsc().
Suggested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/fd43e16281991f096c1e4d21574d9e1402c62d39.1434501121.git.luto@kernel.org
[ Ported it to v4.2-rc1. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
It has no more callers, and it was never a very sensible
interface to begin with. Users of the TSC should either read all
64 bits or explicitly throw out the high bits.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/250105f7cee519be9d7fc4464b5784caafc8f4fe.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
They have no users. Leave native_read_tscp() which seems
potentially useful despite also having no callers.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/6abfa3ef80534b5d73898a48c4d25e069303cbe5.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Now that the ->read_tsc() paravirt hook is gone, rdtscll() is
just a wrapper around native_read_tsc(). Unwrap it.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/d2449ae62c1b1fb90195bcfb19ef4a35883a04dc.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We've had ->read_tsc() and ->read_tscp() paravirt hooks since
the very beginning of paravirt, i.e.,
d3561b7fa0 ("[PATCH] paravirt: header and stubs for paravirtualisation").
AFAICT, the only paravirt guest implementation that ever
replaced these calls was vmware, and it's gone. Arguably even
vmware shouldn't have hooked RDTSC -- we fully support systems
that don't have a TSC at all, so there's no point for a paravirt
implementation to pretend that we have a TSC but to replace it.
I also doubt that these hooks actually worked. Calls to rdtscl()
and rdtscll(), which respected the hooks, were used seemingly
interchangeably with native_read_tsc(), which did not.
Just remove them. If anyone ever needs them again, they can try
to make a case for why they need them.
Before, on a paravirt config:
text data bss dec hex filename
12618257 1816384 1093632 15528273 ecf151 vmlinux
After:
text data bss dec hex filename
12617207 1816384 1093632 15527223 eced37 vmlinux
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: virtualization@lists.linux-foundation.org
Link: http://lkml.kernel.org/r/d08a2600fb298af163681e5efd8e599d889a5b97.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In the following commit:
cdc7957d19 ("x86: move native_read_tsc() offline")
... native_read_tsc() was moved out of line, presumably for some
now-obsolete vDSO-related reason. Undo it.
The entire rdtsc, shl, or sequence is only 11 bytes, and calls
via rdtscl() and similar helpers were already inlined.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/d05ffe2aaf8468ca475ebc00efad7b2fa174af19.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This header containing all MSRs and respective bit definitions
got exported to userspace in conjunction with the big UAPI
shuffle.
But, it doesn't belong in the UAPI headers because userspace can
do its own MSR defines and exporting them from the kernel blocks
us from doing cleanups/renames in that header. Which is
ridiculous - it is not kernel's job to export such a header and
keep MSRs list and their names stable.
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1433436928-31903-19-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The wrmsrl_safe macro performs invalid shifts if the value
argument is 32 bits. This makes it unnecessarily awkward to
write code that puts an unsigned long into an MSR.
Convert it to a real inline function.
For inspiration, see:
7c74d5b7b7 ("x86/asm/entry/64: Fix MSR_IA32_SYSENTER_CS MSR value").
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: <linux-kernel@vger.kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
[ Applied small improvements. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We very often need to set or clear a bit in an MSR as a result of doing
some sort of a hardware configuration. Add generic versions of that
repeated functionality in order to save us a bunch of duplicated code in
the early CPU vendor detection/config code.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1394384725-10796-2-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Having 64-bit MSR access methods on given CPU can avoid shifting and
simplify MSR content manipulation. We already have other combinations
of rdmsrl_xxx and wrmsrl_xxx but missing the _on_cpu version.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Reviewed-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Make sure all MSR-accessing primitives which split MSR values in
two 32-bit parts have their variables called 'low' and 'high' for
consistence with the rest of the code and for ease of staring.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1362428180-8865-5-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Michael Kerrisk <mtk.manpages@gmail.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Jones <davej@redhat.com>
Rename checking_wrmsrl() to wrmsrl_safe(), to match the naming
convention used by all the other MSR access functions/macros.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Now that all users of {rd,wr}msr_amd_safe have been fixed, deprecate its
use by making them private to amd.c and adding warnings when used on
anything else beside K8.
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1338562358-28182-5-git-send-email-bp@amd64.org
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
There were paravirt_ops hooks for the full register set variant of
{rd,wr}msr_safe which are actually not used by anyone anymore. Remove
them to make the code cleaner and avoid silent breakages when the pvops
members were uninitialized. This has been boot-tested natively and under
Xen with PVOPS enabled and disabled on one machine.
Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Link: http://lkml.kernel.org/r/1338562358-28182-2-git-send-email-bp@amd64.org
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Recently, I got bitten by using rdmsr_safe too early in the boot
process. Document its shortcomings for future reference.
Link: http://lkml.kernel.org/r/4ED5B70F.606@lwfinger.net
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Avoids quite a lot of warnings with a gcc 4.6 -Wall build
because this happens in a commonly used header file (apic.h)
Signed-off-by: Andi Kleen <ak@linux.intel.com>
LKML-Reference: <201007202219.o6KMJme6021066@imap1.linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Randy Dunlap reported the following build error:
"When CONFIG_SMP=n, CONFIG_X86_MSR=m:
ERROR: "msrs_free" [drivers/edac/amd64_edac_mod.ko] undefined!
ERROR: "msrs_alloc" [drivers/edac/amd64_edac_mod.ko] undefined!"
This is due to the fact that <arch/x86/lib/msr.c> is conditioned on
CONFIG_SMP and in the UP case we have only the stubs in the header.
Fork off SMP functionality into a new file (msr-smp.c) and build
msrs_{alloc,free} unconditionally.
Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
LKML-Reference: <20091216231625.GD27228@liondog.tnic>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Clean up write_tsc() and write_tscp_aux() by replacing
hardcoded values.
No change in functionality.
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
LKML-Reference: <1260942485-19156-4-git-send-email-sheng@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The current rd/wrmsr_on_cpus helpers assume that the supplied
cpumasks are contiguous. However, there are machines out there
like some K8 multinode Opterons which have a non-contiguous core
enumeration on each node (e.g. cores 0,2 on node 0 instead of 0,1), see
http://www.gossamer-threads.com/lists/linux/kernel/1160268.
This patch fixes out-of-bounds writes (see URL above) by adding per-CPU
msr structs which are used on the respective cores.
Additionally, two helpers, msrs_{alloc,free}, are provided for use by
the callers of the MSR accessors.
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Doug Thompson <dougthompson@xmission.com>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
LKML-Reference: <20091211171440.GD31998@aftab>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This makes the declarations match the definitions, which already
use 'struct cpumask'.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Borislav Petkov <borislav.petkov@amd.com>
LKML-Reference: <200911052245.41803.rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Since rdmsr_on_cpus and wrmsr_on_cpus are almost identical, unify them
into a common __rwmsr_on_cpus helper thus avoiding code duplication.
While at it, convert cpumask_t's to const struct cpumask *.
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Make it possible to access the all-register-setting/getting MSR
functions via the MSR driver. This is implemented as an ioctl() on
the standard MSR device node.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Borislav Petkov <petkovbb@gmail.com>
Create _on_cpu helpers for {rw,wr}msr_safe_regs() analogously with the
other MSR functions. This will be necessary to add support for these
to the MSR driver.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Borislav Petkov <petkovbb@gmail.com>
For some reason, the _safe MSR functions returned -EFAULT, not -EIO.
However, the only user which cares about the return code as anything
other than a boolean is the MSR driver, which wants -EIO. Change it
to -EIO across the board.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Switch them to native_{rd,wr}msr_safe_regs and remove
pv_cpu_ops.read_msr_amd.
Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
LKML-Reference: <1251705011-18636-2-git-send-email-petkovbb@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
native_{rdmsr,wrmsr}_safe_regs are two new interfaces which allow
presetting of a subset of eight x86 GPRs before executing the rd/wrmsr
instructions. This is needed at least on AMD K8 for accessing an erratum
workaround MSR.
Originally based on an idea by H. Peter Anvin.
Signed-off-by: Borislav Petkov <petkovbb@gmail.com>
LKML-Reference: <1251705011-18636-1-git-send-email-petkovbb@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
<linux/types.h> is only required for __KERNEL__ as whole file is covered with it
Also fixed some spacing issues for usr/include/asm-x86/msr.h
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Cc: "H. Peter Anvin" <hpa@kernel.org>
LKML-Reference: <1245228070.2662.1.camel@ht.satnam>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Provide for concurrent MSR writes on all the CPUs in the cpumask. Also,
add a temporary workaround for smp_call_function_many which skips the
CPU we're executing on.
Bart: zero out rv struct which is allocated on stack.
CC: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Add a struct representing a 64bit MSR pair consisting of a low and high
register part and convert msr_info to use it. Also, rename msr-on-cpu.c
to msr.c.
Side note: Put the cpumask.h include in __KERNEL__ space thus fixing an
allmodconfig build failure in the headers_check target.
CC: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
* 'tracing-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (241 commits)
sched, trace: update trace_sched_wakeup()
tracing/ftrace: don't trace on early stage of a secondary cpu boot, v3
Revert "x86: disable X86_PTRACE_BTS"
ring-buffer: prevent false positive warning
ring-buffer: fix dangling commit race
ftrace: enable format arguments checking
x86, bts: memory accounting
x86, bts: add fork and exit handling
ftrace: introduce tracing_reset_online_cpus() helper
tracing: fix warnings in kernel/trace/trace_sched_switch.c
tracing: fix warning in kernel/trace/trace.c
tracing/ring-buffer: remove unused ring_buffer size
trace: fix task state printout
ftrace: add not to regex on filtering functions
trace: better use of stack_trace_enabled for boot up code
trace: add a way to enable or disable the stack tracer
x86: entry_64 - introduce FTRACE_ frame macro v2
tracing/ftrace: add the printk-msg-only option
tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp()
x86, bts: correctly report invalid bts records
...
Fixed up trivial conflict in scripts/recordmcount.pl due to SH bits
being already partly merged by the SH merge.
Impact: fix a crash/hard-reboot on certain configs while enabling cpu runtime
On some archs, the boot of a secondary cpu can have an early fragile state.
On x86-64, the pda is not initialized on the first stage of a cpu boot but
it is needed to get the cpu number and the current task pointer. This data
is needed during tracing. As they were dereferenced at this stage, we got a
crash while tracing a cpu being enabled at runtime.
Some other archs like ia64 can have such kind of issue too.
Changes on v2:
We dropped the previous solution of a per-arch called function to guess the
current state of a cpu. That could slow down the tracing.
This patch removes the -pg flag on arch/x86/kernel/cpu/common.c where
the low level cpu boot functions exist, on start_secondary() and a helper
function used at this stage.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: micro-optimization
Is there any reason why x86 rdtscll have to use the out of line
function instead of inline __native_read_tsc()? native_read_tsc and
__native_read_tsc is essentially the same functions.
Patch to let x86 rdtscll() to use the inline version of read_tsc.
Signed-off-by: Ken Chen <kenchen@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
in scheduler-intense workloads native_read_tsc() overhead accounts for
20% of the system overhead:
659567 system_call 41222.9375
686796 schedule 435.7843
718382 __switch_to 665.1685
823875 switch_mm 4526.7857
1883122 native_read_tsc 55385.9412
9761990 total 2.8468
this is large part due to the rdtsc_barrier() that is done before
and after reading the TSC.
But sched_clock() is not a precise clock in the GTOD sense, using such
barriers is completely pointless. So remove the barriers and only use
them in vget_cycles().
This improves lat_ctx performance by about 5%.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The rdmsr instruction(et al) for i386 and x86-64 are semantically same.
The only difference is how gcc interpret constraint "A" for these targets.
Signed-off-by: Jike Song <albcamus@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Change header guards named "ASM_X86__*" to "_ASM_X86_*" since:
a. the double underscore is ugly and pointless.
b. no leading underscore violates namespace constraints.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
