Commit 9ce815ed authored Dec 23, 2015 by Chris Metcalf

tile: fix bug in setting PT_FLAGS_DISABLE_IRQ on kernel entry



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>

parent acfb699e

arch/tile/kernel/intvec_64.S

+1 −1

Original line number	Diff line number	Diff line
		@@ -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 */