Merge tag 'powerpc-4.12-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc...

[linux-2.6-block.git] / arch / powerpc / kernel / idle_book3s.S

diff --git a/arch/powerpc/kernel/idle_book3s.S b/arch/powerpc/kernel/idle_book3s.S
index 0cdee271dd932e613f7dcbf70897a37d072425a2..07d4e0ad60db5b1a1f2cd5da08763a3acea7ea3b 100644 (file)
--- a/arch/powerpc/kernel/idle_book3s.S
+++ b/arch/powerpc/kernel/idle_book3s.S
@@ -543,9 +543,23 @@ pnv_restore_hyp_resource_arch207:
 pnv_wakeup_tb_loss:
        ld      r1,PACAR1(r13)
        /*
-        * Before entering any idle state, the NVGPRs are saved in the stack
-        * and they are restored before switching to the process context. Hence
-        * until they are restored, they are free to be used.
+        * Before entering any idle state, the NVGPRs are saved in the stack.
+        * If there was a state loss, or PACA_NAPSTATELOST was set, then the
+        * NVGPRs are restored. If we are here, it is likely that state is lost,
+        * but not guaranteed -- neither ISA207 nor ISA300 tests to reach
+        * here are the same as the test to restore NVGPRS:
+        * PACA_THREAD_IDLE_STATE test for ISA207, PSSCR test for ISA300,
+        * and SRR1 test for restoring NVGPRs.
+        *
+        * We are about to clobber NVGPRs now, so set NAPSTATELOST to
+        * guarantee they will always be restored. This might be tightened
+        * with careful reading of specs (particularly for ISA300) but this
+        * is already a slow wakeup path and it's simpler to be safe.
+        */
+       li      r0,1
+       stb     r0,PACA_NAPSTATELOST(r13)
+
+       /*
         *
         * Save SRR1 and LR in NVGPRs as they might be clobbered in
         * opal_call() (called in CHECK_HMI_INTERRUPT). SRR1 is required