linux-kernel - Re: [RFC, PATCH 05/12] KVM: TDX: Add tdx_pamt

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Message-ID: <aBqxBmHtpSipnULS@yzhao56-desk.sh.intel.com>
Date: Wed, 7 May 2025 09:01:58 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: "Huang, Kai" <kai.huang@...el.com>
CC: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
	"bp@...en8.de" <bp@...en8.de>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>, "x86@...nel.org" <x86@...nel.org>,
	"mingo@...hat.com" <mingo@...hat.com>, "tglx@...utronix.de"
	<tglx@...utronix.de>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>, "Yamahata, Isaku"
	<isaku.yamahata@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [RFC, PATCH 05/12] KVM: TDX: Add tdx_pamt_get()/put() helpers

On Mon, May 05, 2025 at 08:44:26PM +0800, Huang, Kai wrote:
> On Fri, 2025-05-02 at 16:08 +0300, Kirill A. Shutemov wrote:
> > +static int tdx_pamt_add(atomic_t *pamt_refcount, unsigned long hpa,
> > +			struct list_head *pamt_pages)
> > +{
> > +	u64 err;
> > +
> > +	hpa = ALIGN_DOWN(hpa, SZ_2M);
> > +
> > +	spin_lock(&pamt_lock);
> 
> Just curious, Can the lock be per-2M-range?
Me too.
Could we introduce smaller locks each covering a 2M range?

And could we deposit 2 pamt pages per-2M hpa range no matter if it's finally
mapped as a huge page or not?