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Date: Fri, 18 Dec 2020 07:33:03 -0800 From: Dave Hansen <dave.hansen@...el.com> To: Ira Weiny <ira.weiny@...el.com> Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Dave Hansen <dave.hansen@...ux.intel.com>, Fenghua Yu <fenghua.yu@...el.com>, x86@...nel.org, linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, linux-doc@...r.kernel.org, linux-nvdimm@...ts.01.org, linux-mm@...ck.org, linux-kselftest@...r.kernel.org, Dan Williams <dan.j.williams@...el.com>, Greg KH <gregkh@...uxfoundation.org> Subject: Re: [NEEDS-REVIEW] [PATCH V3 04/10] x86/pks: Preserve the PKRS MSR on context switch On 12/17/20 8:10 PM, Ira Weiny wrote: > On Thu, Dec 17, 2020 at 12:41:50PM -0800, Dave Hansen wrote: >> On 11/6/20 3:29 PM, ira.weiny@...el.com wrote: >>> void disable_TSC(void) >>> @@ -644,6 +668,8 @@ void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p) >>> >>> if ((tifp ^ tifn) & _TIF_SLD) >>> switch_to_sld(tifn); >>> + >>> + pks_sched_in(); >>> } >> >> Does the selftest for this ever actually schedule()? > > At this point I'm not sure. This code has been in since the beginning. So its > seen a lot of soak time. Think about it another way. Let's say this didn't get called on the first context switch away from the PKS-using task. Would anyone notice? How likely is this to happen? The function tracers or kprobes tend to be a great tool for this, at least for testing whether the code path you expect to hit is getting hit.
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