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

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Message-ID: <jz5qs2gx32jeuby4gvrbt4m6m3dnhwphmj7fqflwy2mf52timq@6grx6bxkdnvn>
Date: Wed, 14 May 2025 09:25:40 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Chao Gao <chao.gao@...el.com>
Cc: pbonzini@...hat.com, seanjc@...gle.com, rick.p.edgecombe@...el.com, 
	isaku.yamahata@...el.com, kai.huang@...el.com, yan.y.zhao@...el.com, tglx@...utronix.de, 
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, kvm@...r.kernel.org, 
	x86@...nel.org, linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [RFC, PATCH 05/12] KVM: TDX: Add tdx_pamt_get()/put() helpers

On Wed, May 14, 2025 at 01:33:38PM +0800, Chao Gao wrote:
> >+static void tdx_pamt_put(struct page *page)
> >+{
> >+	unsigned long hpa = page_to_phys(page);
> >+	atomic_t *pamt_refcount;
> >+	LIST_HEAD(pamt_pages);
> >+	u64 err;
> >+
> >+	if (!tdx_supports_dynamic_pamt(tdx_sysinfo))
> >+		return;
> >+
> >+	hpa = ALIGN_DOWN(hpa, SZ_2M);
> >+
> >+	pamt_refcount = tdx_get_pamt_refcount(hpa);
> >+	if (!atomic_dec_and_test(pamt_refcount))
> >+		return;
> >+
> >+	spin_lock(&pamt_lock);
> >+
> >+	/* Lost race against tdx_pamt_add()? */
> >+	if (atomic_read(pamt_refcount) != 0) {
> >+		spin_unlock(&pamt_lock);
> >+		return;
> >+	}
> >+
> >+	err = tdh_phymem_pamt_remove(hpa | TDX_PS_2M, &pamt_pages);
> >+	spin_unlock(&pamt_lock);
> >+
> >+	if (err) {
> >+		pr_tdx_error(TDH_PHYMEM_PAMT_REMOVE, err);
> 
> Should the refcount be increased here, since the PAMT pages are not removed?

Right. Thanks.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov