linux-kernel - Re: [PATCH v10 015/108] x86/cpu: Add helper functions to allocate/free TDX private host key id

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Message-ID: <b145dc3fcf5b2fd29241f4c8b5286b71402c7d7e.camel@intel.com>
Date:   Tue, 8 Nov 2022 09:16:57 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
Subject: Re: [PATCH v10 015/108] x86/cpu: Add helper functions to
 allocate/free TDX private host key id

On Sat, 2022-10-29 at 23:22 -0700, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> TDX private host key id is assigned to guest TD.  The memory controller
> encrypts guest TD memory with the assigned TDX private host key id (HIKD).
								     ^
								     HKID.

And since you already mentioned in the first sentence, you can put (HKID) part
there.  And I think you can just use HKID in the rest places to save some typing
as this is the purpose of using (HKID) I suppose.

[...]

>  
> +/* TDX KeyID pool */
> +static DEFINE_IDA(tdx_keyid_pool);
> +
> +int tdx_keyid_alloc(void)
> +{
> +	if (WARN_ON_ONCE(!tdx_keyid_start || !tdx_keyid_num))
> +		return -EINVAL;
> +
> +	/* The first keyID is reserved for the global key. */
> +	return ida_alloc_range(&tdx_keyid_pool, tdx_keyid_start + 1,
> +			       tdx_keyid_start + tdx_keyid_num - 1,
> +			       GFP_KERNEL);
> +}
> +EXPORT_SYMBOL_GPL(tdx_keyid_alloc);
> +
> +void tdx_keyid_free(int keyid)
> +{
> +	/* keyid = 0 is reserved. */
> +	if (!keyid || keyid <= 0)
> +		return;

Double check of keyid == 0.

I think you can just use:

	if (keyid <= tdx_keyid_start)
		return;

And/or add a WARN() as it's a bug if above happens.

> +
> +	ida_free(&tdx_keyid_pool, keyid);
> +}
> +EXPORT_SYMBOL_GPL(tdx_keyid_free);
> +
>  static void __init tdx_memory_destroy(void)
>  {
>  	while (!list_empty(&tdx_memlist)) {