From 2babd6ea43edacfc1577432baa187a7d212f3f4f Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Wed, 26 Feb 2020 03:35:25 +1000
Subject: [PATCH] powerpc/64s/exception: Avoid touching the stack in
hdecrementer
References: jsc#SLE-9246
Patch-mainline: v5.7-rc1
Git-commit: 2babd6ea43edacfc1577432baa187a7d212f3f4f
The hdec interrupt handler is reported to sometimes fire in Linux if
KVM leaves it pending after a guest exists. This is harmless, so there
is a no-op handler for it.
The interrupt handler currently uses the regular kernel stack. Change
this to avoid touching the stack entirely.
This should be the last place where the regular Linux stack can be
accessed with asynchronous interrupts (including PMI) soft-masked.
It might be possible to take advantage of this invariant, e.g., to
context switch the kernel stack SLB entry without clearing MSR[EE].
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200225173541.1549955-17-npiggin@gmail.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
arch/powerpc/include/asm/time.h | 1 -
arch/powerpc/kernel/exceptions-64s.S | 25 ++++++++++++++++++++-----
arch/powerpc/kernel/time.c | 9 ---------
3 files changed, 20 insertions(+), 15 deletions(-)
diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h
index 08dbe3e6831c..e0107495c4de 100644
--- a/arch/powerpc/include/asm/time.h
+++ b/arch/powerpc/include/asm/time.h
@@ -24,7 +24,6 @@ extern struct clock_event_device decrementer_clockevent;
extern void generic_calibrate_decr(void);
-extern void hdec_interrupt(struct pt_regs *regs);
/* Some sane defaults: 125 MHz timebase, 1GHz processor */
extern unsigned long ppc_proc_freq;
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index da15ec4fc8cb..146afa0922fb 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1507,6 +1507,8 @@ EXC_COMMON_BEGIN(decrementer_common)
INT_DEFINE_BEGIN(hdecrementer)
IVEC=0x980
IHSRR=EXC_HV
+ ISTACK=0
+ IRECONCILE=0
IKVM_REAL=1
IKVM_VIRT=1
INT_DEFINE_END(hdecrementer)
@@ -1518,11 +1520,24 @@ EXC_VIRT_BEGIN(hdecrementer, 0x4980, 0x80)
GEN_INT_ENTRY hdecrementer, virt=1
EXC_VIRT_END(hdecrementer, 0x4980, 0x80)
EXC_COMMON_BEGIN(hdecrementer_common)
- GEN_COMMON hdecrementer
- bl save_nvgprs
- addi r3,r1,STACK_FRAME_OVERHEAD
- bl hdec_interrupt
- b ret_from_except
+ __GEN_COMMON_ENTRY hdecrementer
+ /*
+ * Hypervisor decrementer interrupts not caught by the KVM test
+ * shouldn't occur but are sometimes left pending on exit from a KVM
+ * guest. We don't need to do anything to clear them, as they are
+ * edge-triggered.
+ *
+ * Be careful to avoid touching the kernel stack.
+ */
+ ld r10,PACA_EXGEN+EX_CTR(r13)
+ mtctr r10
+ mtcrf 0x80,r9
+ ld r9,PACA_EXGEN+EX_R9(r13)
+ ld r10,PACA_EXGEN+EX_R10(r13)
+ ld r11,PACA_EXGEN+EX_R11(r13)
+ ld r12,PACA_EXGEN+EX_R12(r13)
+ ld r13,PACA_EXGEN+EX_R13(r13)
+ HRFI_TO_KERNEL
GEN_KVM hdecrementer
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 1168e8b37e30..bda9cb4a0a5f 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -663,15 +663,6 @@ void timer_broadcast_interrupt(void)
}
#endif
-/*
- * Hypervisor decrementer interrupts shouldn't occur but are sometimes
- * left pending on exit from a KVM guest. We don't need to do anything
- * to clear them, as they are edge-triggered.
- */
-void hdec_interrupt(struct pt_regs *regs)
-{
-}
-
#ifdef CONFIG_SUSPEND
static void generic_suspend_disable_irqs(void)
{
--
2.28.0