linux-kernel - Re: [PATCHv10.1 09/18] x86/mm: Adding callbacks to prepare encrypted memory for kexec

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Message-ID: <ch244dd4k5nu5rcryuwqp4pztl4dduhciqunin5drr7a3yls2h@siisliaoc2f6>
Date: Mon, 6 May 2024 16:22:02 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Borislav Petkov <bp@...en8.de>
Cc: adrian.hunter@...el.com, ashish.kalra@....com, bhe@...hat.com, 
	dave.hansen@...ux.intel.com, elena.reshetova@...el.com, jun.nakajima@...el.com, 
	kai.huang@...el.com, kexec@...ts.infradead.org, linux-coco@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, ltao@...hat.com, mingo@...hat.com, nik.borisov@...e.com, 
	peterz@...radead.org, rafael@...nel.org, rick.p.edgecombe@...el.com, 
	sathyanarayanan.kuppuswamy@...ux.intel.com, seanjc@...gle.com, tglx@...utronix.de, thomas.lendacky@....com, 
	x86@...nel.org
Subject: Re: [PATCHv10.1 09/18] x86/mm: Adding callbacks to prepare encrypted
 memory for kexec

On Thu, May 02, 2024 at 03:45:06PM +0200, Borislav Petkov wrote:
> > diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
> > index e74d0c4286c1..f1b261be78b4 100644
> > --- a/arch/x86/kernel/crash.c
> > +++ b/arch/x86/kernel/crash.c
> > @@ -128,6 +128,10 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
> >  #ifdef CONFIG_HPET_TIMER
> >  	hpet_disable();
> >  #endif
> > +
> > +	x86_platform.guest.enc_kexec_stop_conversion(true);
> > +	x86_platform.guest.enc_kexec_unshare_mem();
> > +
> 
> You call them here back-to-back...
> 
> >  	crash_save_cpu(regs, safe_smp_processor_id());
> >  }
> >  
> > diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
> > index f3130f762784..c1920ec34f0c 100644
> > --- a/arch/x86/kernel/reboot.c
> > +++ b/arch/x86/kernel/reboot.c
> > @@ -12,6 +12,7 @@
> >  #include <linux/delay.h>
> >  #include <linux/objtool.h>
> >  #include <linux/pgtable.h>
> > +#include <linux/kexec.h>
> >  #include <acpi/reboot.h>
> >  #include <asm/io.h>
> >  #include <asm/apic.h>
> > @@ -716,6 +717,14 @@ static void native_machine_emergency_restart(void)
> >  
> >  void native_machine_shutdown(void)
> >  {
> > +	/*
> > +	 * Call enc_kexec_stop_conversion() while all CPUs are still active and
> > +	 * interrupts are enabled. This will allow all in-flight memory
> > +	 * conversions to finish cleanly.
> > +	 */
> > +	if (kexec_in_progress)
> > +		x86_platform.guest.enc_kexec_stop_conversion(false);
> > +
> >  	/* Stop the cpus and apics */
> >  #ifdef CONFIG_X86_IO_APIC
> >  	/*
> > @@ -752,6 +761,9 @@ void native_machine_shutdown(void)
> >  #ifdef CONFIG_X86_64
> >  	x86_platform.iommu_shutdown();
> >  #endif
> > +
> > +	if (kexec_in_progress)
> > +		x86_platform.guest.enc_kexec_unshare_mem();
> 
> ... but they're split here.
> 
> And I don't know why and nothing tells me...

I do. See comment just above enc_kexec_stop_conversion() call.

Do you want also comment for enc_kexec_unshare_mem() ?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov