From d38014eaac512761cb9ffa552247a888bf30a2c3 Mon Sep 17 00:00:00 2001
From: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Date: Wed, 26 Jul 2017 02:30:16 -0300
Subject: [PATCH] drm/i915: Handle msr read failure gracefully
Git-commit: d38014eaac512761cb9ffa552247a888bf30a2c3
Patch-mainline: v4.14-rc1
References: FATE#322643 bsc#1055900
When reading the i915_energy_uJ debugfs file, it tries to fetch
MSR_RAPL_POWER_UNIT, which might not be available, like in a vm
environment, causing the exception shown below.
We can easily prevent it by doing a rdmsrl_safe read instead, which will
handle the exception, allowing us to abort the debugfs file read.
This was caught by the new igt@debugfs_test@read_all_entries testcase in
the CI.
unchecked MSR access error: RDMSR from 0x606 at rIP:0xffffffffa0078f66
(i915_energy_uJ+0x36/0xb0 [i915])
Call Trace:
seq_read+0xdc/0x3a0
full_proxy_read+0x4f/0x70
__vfs_read+0x23/0x120
? putname+0x4f/0x60
? rcu_read_lock_sched_held+0x75/0x80
? entry_SYSCALL_64_fastpath+0x5/0xb1
vfs_read+0xa0/0x150
SyS_read+0x44/0xb0
entry_SYSCALL_64_fastpath+0x1c/0xb1
RIP: 0033:0x7f1f5e9f4500
RSP: 002b:00007ffc77e65cf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: ffffffff8146e003 RCX: 00007f1f5e9f4500
RDX: 0000000000000200 RSI: 00007ffc77e65d10 RDI: 0000000000000006
RBP: ffffc900007abf88 R08: 0000000001eaff20 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000006 R14: 0000000000000005 R15: 0000000001eb94db
? __this_cpu_preempt_check+0x13/0x20
V2: - Drop unsigned long long cast and improve calculation (Chris)
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101901
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/87o9s7zrx3.fsf@dilma.collabora.co.uk
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/i915_debugfs.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -2783,7 +2783,7 @@ out:
static int i915_energy_uJ(struct seq_file *m, void *data)
{
struct drm_i915_private *dev_priv = node_to_i915(m->private);
- u64 power;
+ unsigned long long power;
u32 units;
if (INTEL_GEN(dev_priv) < 6)
@@ -2791,15 +2791,18 @@ static int i915_energy_uJ(struct seq_fil
intel_runtime_pm_get(dev_priv);
- rdmsrl(MSR_RAPL_POWER_UNIT, power);
- power = (power & 0x1f00) >> 8;
- units = 1000000 / (1 << power); /* convert to uJ */
+ if (rdmsrl_safe(MSR_RAPL_POWER_UNIT, &power)) {
+ intel_runtime_pm_put(dev_priv);
+ return -ENODEV;
+ }
+
+ units = (power & 0x1f00) >> 8;
power = I915_READ(MCH_SECP_NRG_STTS);
- power *= units;
+ power = (1000000 * power) >> units; /* convert to uJ */
intel_runtime_pm_put(dev_priv);
- seq_printf(m, "%llu", (long long unsigned)power);
+ seq_printf(m, "%llu", power);
return 0;
}