From: Juergen Gross <jgross@suse.com>
To: Borislav Petkov <bp@alien8.de>
Cc: xen-devel@lists.xenproject.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v3 08/10] x86/mtrr: let cache_aps_delayed_init replace mtrr_aps_delayed_init
Date: Fri, 30 Sep 2022 15:11:07 +0200 [thread overview]
Message-ID: <2e843e28-2836-910e-bcd8-f35872adf21a@suse.com> (raw)
In-Reply-To: <YzbZJEeVHkTnWIfc@zn.tnic>
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On 30.09.22 13:55, Borislav Petkov wrote:
> On Thu, Sep 29, 2022 at 10:26:59AM +0200, Juergen Gross wrote:
>> So right now I'm inclined to be better on the safe side by not adding any
>> cpu hotplug hook, but to use just the same "delayed AP init" flag as today,
>> just renaming it. This would leave the delayed MTRR/PAT init in place for
>> resume and kexec cases, but deferring the MTRR/PAT cleanup due to this
>> potential issue seems not appropriate, as the cleanup isn't changing the
>> behavior here.
>
> Ok, what's wrong with adding a special hotplug level just for that thing
> and running it very early? Practically pretty much where it was in time,
> in identify_secondary_cpu()?
Yes, this can be done. It would practically have to be the first one just
after CPUHP_BRINGUP_CPU.
The question is whether we really want to call the MTRR/PAT initialization
on hotplugged cpus only after enabling interrupts. Note that the callbacks
are activated only at the end of start_secondary(), while today MTRR/PAT
initialization is called some time earlier by:
start_secondary()
smp_callin()
smp_store_cpu_info()
identify_secondary_cpu()
mtrr_ap_init()
I don't think this is a real problem, but I wanted to mention it.
The next question would be, why MTRR/PAT init should be special (meaning:
why are all the other functions called that early not realized via
callbacks)? Is it just because of the special handling during boot/resume?
It might be worth a discussion whether there shouldn't be a special group
of callbacks activated BEFORE interrupts are being enabled.
> Having a special one is warranted, as you explain, I'd say.
Thanks. I'll write a patch for that.
Juergen
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next prev parent reply other threads:[~2022-09-30 13:11 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-08 8:49 [PATCH v3 00/10] x86: make pat and mtrr independent from each other Juergen Gross
2022-09-08 8:49 ` [PATCH v3 01/10] x86/mtrr: add comment for set_mtrr_state() serialization Juergen Gross
2022-09-08 8:49 ` [PATCH v3 02/10] x86/mtrr: remove unused cyrix_set_all() function Juergen Gross
2022-09-08 8:49 ` [PATCH v3 03/10] x86/mtrr: replace use_intel() with a local flag Juergen Gross
2022-09-11 10:16 ` Borislav Petkov
2022-09-12 9:10 ` Juergen Gross
2022-09-19 19:10 ` Borislav Petkov
2022-09-28 10:17 ` Juergen Gross
2022-09-08 8:49 ` [PATCH v3 04/10] x86: move some code out of arch/x86/kernel/cpu/mtrr Juergen Gross
2022-09-11 11:02 ` Borislav Petkov
2022-09-12 9:11 ` Juergen Gross
2022-09-08 8:49 ` [PATCH v3 05/10] x86/mtrr: split generic_set_all() Juergen Gross
2022-09-19 19:25 ` Borislav Petkov
2022-09-08 8:49 ` [PATCH v3 06/10] x86/mtrr: remove set_all callback from struct mtrr_ops Juergen Gross
2022-09-08 8:49 ` [PATCH v3 07/10] x86/mtrr: simplify mtrr_bp_init() Juergen Gross
2022-09-26 18:40 ` Borislav Petkov
2022-09-08 8:49 ` [PATCH v3 08/10] x86/mtrr: let cache_aps_delayed_init replace mtrr_aps_delayed_init Juergen Gross
2022-09-26 21:11 ` Borislav Petkov
2022-09-27 8:57 ` Juergen Gross
2022-09-27 10:10 ` Borislav Petkov
2022-09-27 10:14 ` Juergen Gross
2022-09-27 11:19 ` Borislav Petkov
2022-09-27 11:25 ` Juergen Gross
2022-09-27 12:13 ` Borislav Petkov
2022-09-27 12:21 ` Juergen Gross
2022-09-27 23:16 ` Borislav Petkov
2022-09-28 5:30 ` Juergen Gross
2022-09-28 6:16 ` Juergen Gross
2022-09-28 10:48 ` Borislav Petkov
2022-09-28 11:14 ` Juergen Gross
2022-09-28 11:22 ` Borislav Petkov
2022-09-28 13:43 ` Juergen Gross
2022-09-28 16:12 ` Borislav Petkov
2022-09-28 16:32 ` Juergen Gross
2022-09-28 16:39 ` Borislav Petkov
2022-09-29 8:26 ` Juergen Gross
2022-09-30 11:55 ` Borislav Petkov
2022-09-30 13:11 ` Juergen Gross [this message]
2022-09-30 13:25 ` Borislav Petkov
2022-09-08 8:49 ` [PATCH v3 09/10] x86/mtrr: add a stop_machine() handler calling only cache_cpu_init() Juergen Gross
2022-09-08 8:49 ` [PATCH v3 10/10] x86: decouple pat and mtrr handling Juergen Gross
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