ACK/CMNT: [SRU][Xenial][PATCH 1/3] UBUNTU: SAUCE: x86/speculation: Cleanup IBPB runtime control handling

Tyler Hicks tyhicks at canonical.com
Mon Dec 3 13:14:38 UTC 2018


On December 3, 2018 6:53:50 AM CST, Juerg Haefliger <juerg.haefliger at canonical.com> wrote:
>> > +int set_ibpb_enabled(unsigned int val)
>> > +{
>> > +	int error = 0;
>> > +
>> > +	mutex_lock(&spec_ctrl_mutex);
>> > +
>> > +	/* Only enable IBPB if the CPU supports it */
>> > +	if (boot_cpu_has(X86_FEATURE_IBPB)) {
>> > +		ibpb_enabled = val;
>> > +		pr_info("Spectre V2 : Spectre v2 mitigation: %s Indirect "  
>> 
>> I think the "Spectre V2 : " portion of this message is redundant and
>is
>> also not present in upstream's message which could confuse user or
>> scripts that are looking at log messages. Can it be removed when
>> applying the patch?
>
>This is exactly how upstream reported it until 5 days ago (commit
>4c71a2b6fd7e changed that message format) :-)
>
>$ uname -r
>4.18.0-11-generic
>$ dmesg | grep 'Spectre V2'
>[    0.028000] Spectre V2 : Mitigation: Full generic retpoline
>[    0.028000] Spectre V2 : Spectre v2 / SpectreRSB mitigation: Filling
>RSB on context switch
>[    0.028000] Spectre V2 : Spectre v2 mitigation: Enabling Indirect
>Branch Prediction Barrier
>[    0.028000] Spectre V2 : Enabling Restricted Speculation for
>firmware calls
>
>...Juerg

Ha! We'll, I don't feel strongly about changing it now. I'll leave that up to you to decide.

Tyler



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