From d38014eaac512761cb9ffa552247a888bf30a2c3 Mon Sep 17 00:00:00 2001 From: Gabriel Krisman Bertazi Date: Wed, 26 Jul 2017 02:30:16 -0300 Subject: [PATCH] drm/i915: Handle msr read failure gracefully 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 Link: https://patchwork.freedesktop.org/patch/msgid/87o9s7zrx3.fsf@dilma.collabora.co.uk Reviewed-by: Chris Wilson Signed-off-by: Chris Wilson Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/i915_debugfs.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c index ea50c4a1efae..6480897bcaf4 100644 --- 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_file *m, void *data) 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; } -- 2.20.1