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tile: fix bug in setting PT_FLAGS_DISABLE_IRQ on kernel entry

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This flag value is saved in ptregs and used to decide whether
to disable irqs when returning from the kernel.  Commit 1168df528fe4
("tile: don't assume user privilege is zero") performed a bad
merge from some KVM-enabled code that had not yet been upstreamed.

The only issue with the old code is that we will read the interrupt
mask in more conditions than we need to (e.g., coming from user
space when user space has the Interrupt Critical Section bit set, or
coming from a guest kernel), which is a slow multi-cycle operation.
This change saves those few cycles in the common case.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
This commit is contained in:
Chris Metcalf 2015-12-23 15:02:47 -05:00
parent acfb699e3d
commit 9ce815ed50
1 changed files with 1 additions and 1 deletions
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2
arch/tile/kernel/intvec_64.S
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@ -658,7 +658,7 @@ intvec_\vecname:
*/
mfspr r32, SPR_EX_CONTEXT_K_1
{
IS_KERNEL_EX1(r22, r22)
IS_KERNEL_EX1(r32, r32)
PTREGS_PTR(r21, PTREGS_OFFSET_FLAGS)
}
beqzt r32, 1f /* zero if from user space */