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2014-08-26x86: Replace __get_cpu_var usesChristoph Lameter
__get_cpu_var() is used for multiple purposes in the kernel source. One of them is address calculation via the form &__get_cpu_var(x). This calculates the address for the instance of the percpu variable of the current processor based on an offset. Other use cases are for storing and retrieving data from the current processors percpu area. __get_cpu_var() can be used as an lvalue when writing data or on the right side of an assignment. __get_cpu_var() is defined as : #define __get_cpu_var(var) (*this_cpu_ptr(&(var))) __get_cpu_var() always only does an address determination. However, store and retrieve operations could use a segment prefix (or global register on other platforms) to avoid the address calculation. this_cpu_write() and this_cpu_read() can directly take an offset into a percpu area and use optimized assembly code to read and write per cpu variables. This patch converts __get_cpu_var into either an explicit address calculation using this_cpu_ptr() or into a use of this_cpu operations that use the offset. Thereby address calculations are avoided and less registers are used when code is generated. Transformations done to __get_cpu_var() 1. Determine the address of the percpu instance of the current processor. DEFINE_PER_CPU(int, y); int *x = &__get_cpu_var(y); Converts to int *x = this_cpu_ptr(&y); 2. Same as #1 but this time an array structure is involved. DEFINE_PER_CPU(int, y[20]); int *x = __get_cpu_var(y); Converts to int *x = this_cpu_ptr(y); 3. Retrieve the content of the current processors instance of a per cpu variable. DEFINE_PER_CPU(int, y); int x = __get_cpu_var(y) Converts to int x = __this_cpu_read(y); 4. Retrieve the content of a percpu struct DEFINE_PER_CPU(struct mystruct, y); struct mystruct x = __get_cpu_var(y); Converts to memcpy(&x, this_cpu_ptr(&y), sizeof(x)); 5. Assignment to a per cpu variable DEFINE_PER_CPU(int, y) __get_cpu_var(y) = x; Converts to __this_cpu_write(y, x); 6. Increment/Decrement etc of a per cpu variable DEFINE_PER_CPU(int, y); __get_cpu_var(y)++ Converts to __this_cpu_inc(y) Cc: Thomas Gleixner <tglx@linutronix.de> Cc: x86@kernel.org Acked-by: H. Peter Anvin <hpa@linux.intel.com> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2011-07-18xen/multicall: move *idx fields to start of mc_bufferJeremy Fitzhardinge
The CPU would prefer small offsets. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
2011-07-18xen/multicall: special-case singleton hypercallsJeremy Fitzhardinge
Singleton calls seem to end up being pretty common, so just directly call the hypercall rather than going via multicall. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
2011-07-18xen/multicalls: add unlikely around slowpath in __xen_mc_entry()Jeremy Fitzhardinge
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
2011-07-18xen/multicalls: disable MC_DEBUGJeremy Fitzhardinge
It's useful - and probably should be a config - but its very heavyweight, especially with the tracing stuff to help sort out problems. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
2011-07-18xen/trace: add multicall tracingJeremy Fitzhardinge
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
2011-07-18xen/multicalls: remove debugfs statsJeremy Fitzhardinge
Remove debugfs stats to make way for tracing. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
2011-06-03xen: off by one errors in multicalls.cDan Carpenter
b->args[] has MC_ARGS elements, so the comparison here should be ">=" instead of ">". Otherwise we read past the end of the array one space. CC: stable@kernel.org Signed-off-by: Dan Carpenter <error27@gmail.com> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
2009-02-16x86, xen: do multicall callbacks with interrupts disabledJeremy Fitzhardinge
We can't call the callbacks after enabling interrupts, as we may get a nested multicall call, which would cause a great deal of havok. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-16x86, xen: degrade BUG to WARN when multicall failsJeremy Fitzhardinge
If one of the components of a multicall fails, WARN rather than BUG, to help with debugging. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-02-16x86, xen: record and display initiator of each multicall when debuggingIan Campbell
Store the caller for each multicall so we can report it on failure. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-16xen: whitespace/checkpatch cleanupTej
Impact: cleanup Signed-off-by: Tej <bewith.tej@gmail.com> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-08-21xen: add debugfs supportJeremy Fitzhardinge
Add support for exporting statistics on mmu updates, multicall batching and pv spinlocks into debugfs. The base path is xen/ and each subsystem adds its own directory: mmu, multicalls, spinlocks. In each directory, writing 1 to "zero_stats" will cause the corresponding stats to be zeroed the next time they're updated. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Acked-by: Jan Beulich <jbeulich@novell.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-07-16xen: print backtrace on multicall failureJeremy Fitzhardinge
Print a backtrace if a multicall fails, to help with debugging. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Stephen Tweedie <sct@redhat.com> Cc: Eduardo Habkost <ehabkost@redhat.com> Cc: Mark McLoughlin <markmc@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-06-25xen: add mechanism to extend existing multicallsJeremy Fitzhardinge
Some Xen hypercalls accept an array of operations to work on. In general this is because its more efficient for the hypercall to the work all at once rather than as separate hypercalls (even batched as a multicall). This patch adds a mechanism (xen_mc_extend_args()) to allocate more argument space to the last-issued multicall, in order to extend its argument list. The user of this mechanism is xen/mmu.c, which uses it to extend the args array of mmu_update. This is particularly valuable when doing the update for a large mprotect, which goes via ptep_modify_prot_commit(), but it also manages to batch updates to pgd/pmds as well. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Hugh Dickins <hugh@veritas.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-04-17x86: coding style fixes to arch/x86/xen/multicalls.cPaolo Ciarrocchi
Before: total: 2 errors, 2 warnings, 138 lines checked After: total: 0 errors, 2 warnings, 138 lines checked No code changed: arch/x86/xen/multicalls.o: text data bss dec hex filename 887 2832 0 3719 e87 multicalls.o.before 887 2832 0 3719 e87 multicalls.o.after md5: cf6d72d9db6dc5a3ebe01eec9f05e95f multicalls.o.before.asm cf6d72d9db6dc5a3ebe01eec9f05e95f multicalls.o.after.asm Signed-off-by: Paolo Ciarrocchi <paolo.ciarrocchi@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2007-10-16xen: add some debug output for failed multicallsJeremy Fitzhardinge
Multicalls are expected to never fail, and the normal response to a failed multicall is very terse. In the interests of better debuggability, add some more verbose output. It may be worth turning this off once it all seems more tested. Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
2007-10-16xen: add batch completion callbacksJeremy Fitzhardinge
This adds a mechanism to register a callback function to be called once a batch of hypercalls has been issued. This is typically used to unlock things which must remain locked until the hypercall has taken place. [ Stable folks: pre-req for 2.6.23 bugfix "xen: deal with stale cr3 values when unpinning pagetables" ] Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Stable Kernel <stable@kernel.org>
2007-10-11i386: move xenThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>