linux-kernel - Re: [PATCH v5 15/22] x86/virt/tdx: Allocate and set up PAMTs for TDMRs

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Date:   Wed, 17 Aug 2022 23:43:19 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "Shahar, Sagi" <sagis@...gle.com>
CC:     "Brown, Len" <len.brown@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Wysocki, Rafael J" <rafael.j.wysocki@...el.com>,
        "sathyanarayanan.kuppuswamy@...ux.intel.com" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
Subject: Re: [PATCH v5 15/22] x86/virt/tdx: Allocate and set up PAMTs for
 TDMRs

On Wed, 2022-08-17 at 15:46 -0700, Sagi Shahar wrote:
> > +/*
> > + * Calculate PAMT size given a TDMR and a page size.  The returned
> > + * PAMT size is always aligned up to 4K page boundary.
> > + */
> > +static unsigned long tdmr_get_pamt_sz(struct tdmr_info *tdmr,
> > +                                     enum tdx_page_sz pgsz)
> > +{
> > +       unsigned long pamt_sz;
> > +       int pamt_entry_nr;
>             ^
> This should be an 'unsigned long'. Otherwise you get an integer
> overflow for large memory machines.

Agreed.  Thanks.

> 
> > +
> > +       switch (pgsz) {
> > +       case TDX_PG_4K:
> > +               pamt_entry_nr = tdmr->size >> PAGE_SHIFT;
> > +               break;
> > +       case TDX_PG_2M:
> > +               pamt_entry_nr = tdmr->size >> PMD_SHIFT;
> > +               break;
> > +       case TDX_PG_1G:
> > +               pamt_entry_nr = tdmr->size >> PUD_SHIFT;
> > +               break;
> > +       default:
> > +               WARN_ON_ONCE(1);
> > +               return 0;
> > +       }
> > +
> > +       pamt_sz = pamt_entry_nr * tdx_sysinfo.pamt_entry_size;
> > +       /* TDX requires PAMT size must be 4K aligned */
> > +       pamt_sz = ALIGN(pamt_sz, PAGE_SIZE);
> > +
> > +       return pamt_sz;
> > +}
> > +