linux-kernel - Re: [PATCHv2 04/12] x86/virt/tdx: Add tdx_alloc/free

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Message-ID: <dba2841f-0725-4b58-b633-650201c053b4@intel.com>
Date: Fri, 27 Jun 2025 10:49:34 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	<pbonzini@...hat.com>, <seanjc@...gle.com>, <dave.hansen@...ux.intel.com>
CC: <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 04/12] x86/virt/tdx: Add tdx_alloc/free_page() helpers

On 09/06/2025 22:13, Kirill A. Shutemov wrote:
> +static void tdx_pamt_put(struct page *page, enum pg_level level)
> +{
> +	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;
> +
> +	if (level != PG_LEVEL_4K)
> +		return;
> +
> +	hpa = ALIGN_DOWN(hpa, PMD_SIZE);
> +
> +	pamt_refcount = tdx_get_pamt_refcount(hpa);
> +	if (!atomic_dec_and_test(pamt_refcount))
> +		return;
> +
> +	scoped_guard(spinlock, &pamt_lock) {
> +		/* Lost race against tdx_pamt_add()? */
> +		if (atomic_read(pamt_refcount) != 0)
> +			return;
> +
> +		err = tdh_phymem_pamt_remove(hpa | TDX_PS_2M, &pamt_pages);
> +
> +		if (err) {
> +			atomic_inc(pamt_refcount);
> +			pr_err("TDH_PHYMEM_PAMT_REMOVE failed: %#llx\n", err);
> +			return;
> +		}
> +	}
> +

Won't any pages that have been used need to be cleared
before being freed.

> +	tdx_free_pamt_pages(&pamt_pages);
> +}