KVM: x86/vPMU: refine kvm_pmu err msg when event creation failed
PATCH 1/1 KVM: x86/vPMU: refine kvm_pmu err msg when event creation failed
If a perf_event creation fails due to any reason of the host perf subsystem, it has no chance to log the corresponding event for guest which may cause abnormal sampling data in guest result. In debug mode, this message helps to understand the state of vPMC and we should not limit the number of occurrences.
--- arch/x86/kvm/pmu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
arch/x86/kvm/pmu.c +2 -2
@@ -131,8 +131,8 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, intr ? kvm_perf_overflow_intr : kvm_perf_overflow, pmc);if (IS_ERR (event)) { -printk_once ("kvm_pmu: event creation failed %ld\n" , -PTR_ERR (event)); +pr_debug ("kvm_pmu: event creation failed %ld\n for pmc->idx = %d" , +PTR_ERR (event), pmc->idx);return ; }
Signature · 1 line
2.21.0
Quoted 5 lines · Like Xu
If a
perf_eventcreation fails due to any reason of the host perf subsystem, it has no chance to log the corresponding event for guest which may cause abnormal sampling data in guest result. In debug mode, this message helps to understand the state of vPMC and we should not limit the number of occurrences.
[]
arch/x86/kvm/pmu.c
Quoted 1 line
arch/x86/kvm/pmu.c +0
-0
[]
arch/x86/kvm/pmu.c static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, · line 135
Quoted 8 lines
arch/x86/kvm/pmu.c +2
-2@@ -131,8 +131,8 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, intr ? kvm_perf_overflow_intr : kvm_perf_overflow, pmc);if (IS_ERR (event)) { -printk_once ("kvm_pmu: event creation failed %ld\n" , -PTR_ERR (event)); +pr_debug ("kvm_pmu: event creation failed %ld\n for pmc->idx = %d" , +PTR_ERR (event), pmc->idx);
Perhaps this was written as printk_once to avoid
spamming the log with repeated messages.
Maybe this should use pr_debug_ratelimited.
(and it should also have a \n termination like:)
pr_debug_ratelimited("kvm_pmu: event creation failed %ld for pmc->idx = %d\n",
PTR_ERR(event), pmc->idx);Perhaps Avi Kivity remembers why he wrote it this way.
https://lore.kernel.org/kvm/[email protected]/
Hi Joe,
Quoted 9 lines · Joe Perches
Quoted 5 lines · Like Xu
If a
perf_eventcreation fails due to any reason of the host perf subsystem, it has no chance to log the corresponding event for guest which may cause abnormal sampling data in guest result. In debug mode, this message helps to understand the state of vPMC and we should not limit the number of occurrences.[]
arch/x86/kvm/pmu.c
Quoted 1 line
arch/x86/kvm/pmu.c +0
-0[]
Quoted 11 lines
arch/x86/kvm/pmu.c static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, · line 135
Quoted 8 lines
arch/x86/kvm/pmu.c +2
-2@@ -131,8 +131,8 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type, intr ? kvm_perf_overflow_intr : kvm_perf_overflow, pmc);if (IS_ERR (event)) { -printk_once ("kvm_pmu: event creation failed %ld\n" , -PTR_ERR (event)); +pr_debug ("kvm_pmu: event creation failed %ld\n for pmc->idx = %d" , +PTR_ERR (event), pmc->idx);Perhaps this was written as
printk_onceto avoid
spamming the log with repeated messages.
The spamming case in practice from this messages is very rare but it's logically possible.
Quoted 3 lines
Maybe this should use
pr_debug_ratelimited.
(and it should also have a \n termination like:)
Thanks and it's my mistake, agree on '\n' usage.
Quoted 7 lines
pr_debug_ratelimited("kvm_pmu: event creation failed %ld for pmc->idx = %d\n", PTR_ERR(event), pmc->idx);Perhaps Avi Kivity remembers why he wrote it this way.
https://lore.kernel.org/kvm/[email protected] >>