linux-kernel - Re: [RFC PATCH v5 16/45] x86/virt/tdx: Add tdx_alloc/free_control

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Message-ID: <aYVSu4Yzbqdw/LgE@yzhao56-desk.sh.intel.com>
Date: Fri, 6 Feb 2026 10:32:27 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
CC: Thomas Gleixner <tglx@...nel.org>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	<x86@...nel.org>, Kiryl Shutsemau <kas@...nel.org>, Paolo Bonzini
	<pbonzini@...hat.com>, <linux-kernel@...r.kernel.org>,
	<linux-coco@...ts.linux.dev>, <kvm@...r.kernel.org>, Kai Huang
	<kai.huang@...el.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, "Vishal
 Annapurve" <vannapurve@...gle.com>, Ackerley Tng <ackerleytng@...gle.com>,
	Sagi Shahar <sagis@...gle.com>, Binbin Wu <binbin.wu@...ux.intel.com>,
	Xiaoyao Li <xiaoyao.li@...el.com>, Isaku Yamahata <isaku.yamahata@...el.com>
Subject: Re: [RFC PATCH v5 16/45] x86/virt/tdx: Add
 tdx_alloc/free_control_page() helpers

On Thu, Feb 05, 2026 at 02:35:25PM -0800, Sean Christopherson wrote:
> On Thu, Feb 05, 2026, Yan Zhao wrote:
> > > diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> > > index f6e80aba5895..682c8a228b53 100644
> > > --- a/arch/x86/virt/vmx/tdx/tdx.c
> > > +++ b/arch/x86/virt/vmx/tdx/tdx.c
> > > @@ -1824,6 +1824,50 @@ u64 tdh_mng_rd(struct tdx_td *td, u64 field, u64 *data)
> > >  }
> > >  EXPORT_SYMBOL_FOR_KVM(tdh_mng_rd);
> > >  
> > > +/* Number PAMT pages to be provided to TDX module per 2M region of PA */
> > > +static int tdx_dpamt_entry_pages(void)
> > > +{
> > > +	if (!tdx_supports_dynamic_pamt(&tdx_sysinfo))
> > > +		return 0;
> > > +
> > This function is not invoked when !tdx_supports_dynamic_pamt().
> > So, probably we can just return the count below?
> 
> Or maybe WARN_ON_ONCE() and return 0?  I have no strong preference.
"WARN_ON_ONCE() and return 0" looks good to me.

> > > +	return tdx_sysinfo.tdmr.pamt_4k_entry_size * PTRS_PER_PTE / PAGE_SIZE;
> > > +}
> > > +
> >