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SubjectRe: [PATCH] perf/x86: descriptive failure messages for PMU init
On Fri, Apr 12, 2019 at 03:09:17PM -0400, Bandan Das wrote:
>
> There's a default warning message that gets printed, however,
> there are various failure conditions:
> - a msr read can fail
> - a msr write can fail
> - a msr has an unexpected value
> - all msrs have unexpected values (disable PMU)
>
> Also, commit commit 005bd0077a79 ("perf/x86: Modify error message in
> virtualized environment") completely removed printing the msr in
> question but these messages could be helpful for debugging vPMUs as
> well. Add them back and change them to pr_debugs, this keeps the
> behavior the same for baremetal.
>
> Lastly, use %llx to silence checkpatch

Yuck... if you're debugging a hypervisor, you can bloody well run your
own kernel with additional print slattered around.

The whole make an exception for virt bullshit was already pushing it,
this is just insane.

> @@ -266,12 +282,30 @@ static bool check_hw_exists(void)
> return true;
>
> msr_fail:
> - if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) {
> + if (virt)
> pr_cont("PMU not available due to virtualization, using software events only.\n");
> - } else {
> - pr_cont("Broken PMU hardware detected, using software events only.\n");
> - pr_err("Failed to access perfctr msr (MSR %x is %Lx)\n",
> - reg, val_new);
> + switch (status) {
> + case READ_FAIL:
> + if (virt)
> + pr_debug("Failed to read perfctr msr (MSR %x)\n", reg);
> + else
> + pr_err("Failed to read perfctr msr (MSR %x)\n", reg);
> + break;
> + case WRITE_FAIL:
> + if (virt)
> + pr_debug("Failed to write perfctr msr (MSR %x, wrote: %llx, read: %llx)\n",
> + reg, val, val_new);
> + else
> + pr_err("Failed to write perfctr msr (MSR %x, wrote: %llx, read: %llx)\n",
> + reg, val, val_new);
> + break;
> + case PMU_FAIL:
> + /* fall through for default message */
> + default:
> + if (virt)
> + pr_debug("Broken PMU hardware detected, using software events only.\n");
> + else
> + pr_cont("Broken PMU hardware detected, using software events only.\n");
> }

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