Re: [PATCH v6 06/11] x86/virt/tdx: Optimize tdx_pamt_get/put()

[Chao Gao]

On Mon, May 25, 2026 at 07:35:10PM -0700, Rick Edgecombe wrote:
>@@ -2057,32 +2057,50 @@ static int tdx_pamt_get(kvm_pfn_t pfn)

[snip]

>+	/*
>+	 * Unlike tdx_pamt_put() which uses atomic_dec_and_lock() to
>+	 * atomically handle the 1->0 transition, the get side has no
>+	 * equivalent combined primitive for 0->1. Recheck under the
>+	 * lock since another get may have already done the 0->1
>+	 * transition after both saw atomic_inc_not_zero() fail.
>+	 */
>+	if (atomic_read(pamt_refcount)) {
>+		atomic_inc(pamt_refcount);
>+		spin_unlock(&pamt_lock);
>+		goto out_free;

spin_unlock() can be moved to out_free to avoid repeating it before
each 'goto out_free'.

> 	}
> 
>+	tdx_status = tdh_phymem_pamt_add(pfn, pamt_pages);
>+	if (tdx_status == TDX_SUCCESS) {
>+		/*
>+		 * The refcount is zero, and this locked path is the
>+		 * only way to increase it from 0->1.
>+		 */
>+		atomic_set(pamt_refcount, 1);
>+	} else {
>+		WARN_ON_ONCE(1);
>+		ret = -EIO;
>+		spin_unlock(&pamt_lock);
>+		goto out_free;
>+	}

Reduce indentation for the normal path:

	if (tdx_status != TDX_SUCCESS) {
		WARN_ON_ONCE(1);
		ret = -EIO;
		spin_unlock(&pamt_lock);
		goto out_free;
	}

	/*
	 * The refcount is zero, and this locked path is the
	 * only way to increase it from 0->1.
	 */
	atomic_set(pamt_refcount, 1);


The rest looks good to me.

Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>