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[v1,10/12] powerpc/64s: remove KVM SKIP test from instruction breakpoint handler

Message ID 20210412014845.1517916-11-npiggin@gmail.com (mailing list archive)
State Accepted
Headers show
Series minor KVM fixes and cleanups | expand
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snowpatch_ozlabs/apply_patch success Successfully applied on branch powerpc/merge (d02429becbe77bc4d27a7357afaf28f9294945bb)
snowpatch_ozlabs/checkpatch success total: 0 errors, 0 warnings, 0 checks, 18 lines checked
snowpatch_ozlabs/needsstable success Patch has no Fixes tags

Commit Message

Nicholas Piggin April 12, 2021, 1:48 a.m. UTC 
The code being executed in KVM_GUEST_MODE_SKIP is hypervisor code with
MSR[IR]=0, so the faults of concern are the d-side ones caused by access
to guest context by the hypervisor.

Instruction breakpoint interrupts are not a concern here. It's unlikely
any good would come of causing breaks in this code, but skipping the
instruction that caused it won't help matters (e.g., skip the mtmsr that
sets MSR[DR]=0 or clears KVM_GUEST_MODE_SKIP).

 [Paul notes: "the 0x1300 interrupt was dropped from the architecture a
  long time ago and is not generated by P7, P8, P9 or P10." So add a
  comment about this in the handler code while we're here. ]

Acked-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/exceptions-64s.S | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index a0515cb829c2..358cd4b0c08e 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -2549,11 +2549,16 @@  EXC_REAL_NONE(0x1200, 0x100)
 EXC_VIRT_NONE(0x5200, 0x100)
 #endif
 
-
+/**
+ * Interrupt 0x1300 - Instruction Address Breakpoint Interrupt.
+ * This has been removed from the ISA before 2.01, which is the earliest
+ * 64-bit BookS ISA supported, however the G5 / 970 implements this
+ * interrupt with a non-architected feature available through the support
+ * processor interface.
+ */
 INT_DEFINE_BEGIN(instruction_breakpoint)
 	IVEC=0x1300
 #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
-	IKVM_SKIP=1
 	IKVM_REAL=1
 #endif
 INT_DEFINE_END(instruction_breakpoint)