linux-kernel - RE: [PATCH v6 2/5] x86/kexec: do unconditional WBINVD for bare-metal in relocate

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Message-ID: <BL1PR11MB5978255591A6AE65D617DC5EF7642@BL1PR11MB5978.namprd11.prod.outlook.com>
Date: Thu, 12 Sep 2024 10:38:40 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "Kaplan, David" <David.Kaplan@....com>, "Hansen, Dave"
	<dave.hansen@...el.com>, "bp@...en8.de" <bp@...en8.de>,
	"peterz@...radead.org" <peterz@...radead.org>, "hpa@...or.com"
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	<tglx@...utronix.de>, "kirill.shutemov@...ux.intel.com"
	<kirill.shutemov@...ux.intel.com>
CC: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "x86@...nel.org" <x86@...nel.org>, "dyoung@...hat.com"
	<dyoung@...hat.com>, "sagis@...gle.com" <sagis@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "Williams, Dan
 J" <dan.j.williams@...el.com>, "Lendacky, Thomas" <Thomas.Lendacky@....com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "Kalra, Ashish"
	<Ashish.Kalra@....com>, "Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"bhe@...hat.com" <bhe@...hat.com>, "nik.borisov@...e.com"
	<nik.borisov@...e.com>
Subject: RE: [PATCH v6 2/5] x86/kexec: do unconditional WBINVD for bare-metal
 in relocate_kernel()

> > How about below?
> >
> > --- a/arch/x86/kernel/machine_kexec_64.c
> > +++ b/arch/x86/kernel/machine_kexec_64.c
> > @@ -351,6 +351,11 @@ void machine_kexec(struct kimage *image)
> >          *
> >          * I take advantage of this here by force loading the
> >          * segments, before I zap the gdt with an invalid value.
> > +        *
> > +        * Note this resets GS to 0.  Don't make any function call after
> > +        * here since call depth tracking uses per-cpu variables to
> > +        * operate (relocate_kernel is explicitly ignored by call depth
> > +        * tracking).
> >          */
> 
> Looks good, thanks!
> 
> >
> > Btw, it would be very helpful if you can help to verify this patch
> > doesn't break call depth tracking in your environment.  Thanks!
> 
> Tested it and it seemed fine (kexec worked and disassembly did not show any
> calls after GS is cleared, as expected).
> 

Thanks!  Should I add your Tested-by?