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x86/cpu: Fix typos and improve the comments in sync_core()

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- Fix typos.

- Move the compiler barrier comment to the top, because it's valid for the
  whole function, not just the legacy branch.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200818053130.GA3161093@gmail.com
Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
This commit is contained in:
Ingo Molnar 2020-08-18 07:31:30 +02:00
parent 8610981399
commit 40eb0cb493
1 changed files with 8 additions and 8 deletions
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16
arch/x86/include/asm/sync_core.h
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@ -47,16 +47,19 @@ static inline void iret_to_self(void)
*
* b) Text was modified on a different CPU, may subsequently be
* executed on this CPU, and you want to make sure the new version
* gets executed. This generally means you're calling this in a IPI.
* gets executed. This generally means you're calling this in an IPI.
*
* If you're calling this for a different reason, you're probably doing
* it wrong.
*
* Like all of Linux's memory ordering operations, this is a
* compiler barrier as well.
*/
static inline void sync_core(void)
{
/*
* The SERIALIZE instruction is the most straightforward way to
* do this but it not universally available.
* do this, but it is not universally available.
*/
if (static_cpu_has(X86_FEATURE_SERIALIZE)) {
serialize();
@ -67,10 +70,10 @@ static inline void sync_core(void)
* For all other processors, there are quite a few ways to do this.
* IRET-to-self is nice because it works on every CPU, at any CPL
* (so it's compatible with paravirtualization), and it never exits
* to a hypervisor. The only down sides are that it's a bit slow
* to a hypervisor. The only downsides are that it's a bit slow
* (it seems to be a bit more than 2x slower than the fastest
* options) and that it unmasks NMIs. The "push %cs" is needed
* because, in paravirtual environments, __KERNEL_CS may not be a
* options) and that it unmasks NMIs. The "push %cs" is needed,
* because in paravirtual environments __KERNEL_CS may not be a
* valid CS value when we do IRET directly.
*
* In case NMI unmasking or performance ever becomes a problem,
@ -81,9 +84,6 @@ static inline void sync_core(void)
* CPUID is the conventional way, but it's nasty: it doesn't
* exist on some 486-like CPUs, and it usually exits to a
* hypervisor.
*
* Like all of Linux's memory ordering operations, this is a
* compiler barrier as well.
*/
iret_to_self();
}