linux-kernel - Re: [PATCHv2 02/12] x86/virt/tdx: Allocate page bitmap for Dynamic PAMT

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Message-ID: <x2cuthbn54u2bqxr7sr2pt2zalvuhd3kpovrgzx42xp23wq6mw@pnvgcxs5zm45>
Date: Thu, 26 Jun 2025 12:25:55 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, dave.hansen@...ux.intel.com, 
	rick.p.edgecombe@...el.com, isaku.yamahata@...el.com, kai.huang@...el.com, 
	yan.y.zhao@...el.com, chao.gao@...el.com, tglx@...utronix.de, mingo@...hat.com, 
	bp@...en8.de, kvm@...r.kernel.org, x86@...nel.org, linux-coco@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 02/12] x86/virt/tdx: Allocate page bitmap for Dynamic
 PAMT

On Wed, Jun 25, 2025 at 11:06:16AM -0700, Dave Hansen wrote:
> >  /*
> >   * Locate a NUMA node which should hold the allocation of the @tdmr
> >   * PAMT.  This node will have some memory covered by the TDMR.  The
> > @@ -522,7 +534,16 @@ static int tdmr_set_up_pamt(struct tdmr_info *tdmr,
> >  	 * and the total PAMT size.
> >  	 */
> >  	tdmr_pamt_size = 0;
> > -	for (pgsz = TDX_PS_4K; pgsz < TDX_PS_NR; pgsz++) {
> > +	pgsz = TDX_PS_4K;
> > +
> > +	/* With Dynamic PAMT, PAMT_4K is replaced with a bitmap */
> > +	if (tdx_supports_dynamic_pamt(&tdx_sysinfo)) {
> > +		pamt_size[pgsz] = tdmr_get_pamt_bitmap_sz(tdmr);
> > +		tdmr_pamt_size += pamt_size[pgsz];
> > +		pgsz++;
> > +	}
> 
> This is the wrong place to do this.
> 
> Hide it in tdmr_get_pamt_sz(). Don't inject it in the main code flow
> here and complicate the for loop.

Okay, makes sense.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov