linux-kernel - Re: [PATCH 2/2] x86/snp: Convert shared memory back to private on kexec

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Date: Thu, 22 Feb 2024 12:50:11 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: Ashish Kalra <Ashish.Kalra@....com>, tglx@...utronix.de, 
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, luto@...nel.org, 
	x86@...nel.org, ardb@...nel.org, hpa@...or.com, linux-efi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, rafael@...nel.org, peterz@...radead.org, adrian.hunter@...el.com, 
	sathyanarayanan.kuppuswamy@...ux.intel.com, elena.reshetova@...el.com, jun.nakajima@...el.com, 
	rick.p.edgecombe@...el.com, seanjc@...gle.com, kai.huang@...el.com, bhe@...hat.com, 
	kexec@...ts.infradead.org, linux-coco@...ts.linux.dev, anisinha@...hat.com, 
	michael.roth@....com, bdas@...hat.com, vkuznets@...hat.com, dionnaglaze@...gle.com, 
	jroedel@...e.de, ashwin.kamat@...adcom.com
Subject: Re: [PATCH 2/2] x86/snp: Convert shared memory back to private on
 kexec

On Wed, Feb 21, 2024 at 02:35:13PM -0600, Tom Lendacky wrote:
> > @@ -906,6 +917,206 @@ void snp_accept_memory(phys_addr_t start, phys_addr_t end)
> >   	set_pages_state(vaddr, npages, SNP_PAGE_STATE_PRIVATE);
> >   }
> > +static inline bool pte_decrypted(pte_t pte)
> > +{
> > +	return cc_mkdec(pte_val(pte)) == pte_val(pte);
> > +}
> > +
> 
> This is duplicated in TDX code, arch/x86/coco/tdx/tdx.c, looks like
> something that can go in a header file, maybe mem_encrypt.h.
> 

I think <asm/pgtable.h> is a better fit.

> > +void snp_kexec_stop_conversion(bool crash)
> > +{
> > +	/* Stop new private<->shared conversions */
> > +	conversion_allowed = false;
> > +	crash_requested = crash;
> > +
> > +	/*
> > +	 * Make sure conversion_allowed is cleared before checking
> > +	 * conversions_in_progress.
> > +	 */
> > +	barrier();
> 
> This should be smp_wmb().
> 

Why?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov