linux-kernel - Re: [PATCH 3/4] crypto: ccp - Refactor out sev_fw

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Date:   Fri, 29 Oct 2021 08:48:32 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Peter Gonda <pgonda@...gle.com>
Cc:     David Rientjes <rientjes@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Marc Orr <marcorr@...gle.com>, Joerg Roedel <jroedel@...e.de>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        John Allen <john.allen@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Bonzini <pbonzini@...hat.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] crypto: ccp - Refactor out sev_fw_alloc()

On 10/28/21 12:57 PM, Peter Gonda wrote:
> Creates a helper function sev_fw_alloc() which can be used to allocate
> aligned memory regions for use by the PSP firmware. Currently only used
> for the SEV-ES TMR region but will be used for the SEV_INIT_EX NV memory
> region.
> 
> Signed-off-by: Peter Gonda <pgonda@...gle.com>
> Acked-by: David Rientjes <rientjes@...gle.com>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: Brijesh Singh <brijesh.singh@....com>
> Cc: Marc Orr <marcorr@...gle.com>
> Cc: Joerg Roedel <jroedel@...e.de>
> Cc: Herbert Xu <herbert@...dor.apana.org.au>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: John Allen <john.allen@....com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Paolo Bonzini <pbonzini@...hat.com> (
> Cc: linux-crypto@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>   drivers/crypto/ccp/sev-dev.c | 24 +++++++++++++++++-------
>   1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index e4bc833949a0..b568ae734857 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -141,6 +141,21 @@ static int sev_cmd_buffer_len(int cmd)
>   	return 0;
>   }
>   
> +static void *sev_fw_alloc(unsigned long len)
> +{
> +	const int order = get_order(len);

This should be an unsigned int to match the function definition, but is 
probably not needed given the comment below.

> +	struct page *page;
> +
> +	if (order > MAX_ORDER-1)
> +		return NULL;

I believe alloc_pages() already does this check (and provides a warning 
unless requested not to), so this check isn't needed.

> +
> +	page = alloc_pages(GFP_KERNEL, order);

Without the above check, you can just replace the 'order' variable with 
'get_order(len)'.

Thanks,
Tom

> +	if (!page)
> +		return NULL;
> +
> +	return page_address(page);
> +}
> +
>   static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>   {
>   	struct psp_device *psp = psp_master;
> @@ -1076,7 +1091,6 @@ EXPORT_SYMBOL_GPL(sev_issue_cmd_external_user);
>   void sev_pci_init(void)
>   {
>   	struct sev_device *sev = psp_master->sev_data;
> -	struct page *tmr_page;
>   	int error = 0, rc;
>   
>   	if (!sev)
> @@ -1092,14 +1106,10 @@ void sev_pci_init(void)
>   		sev_get_api_version();
>   
>   	/* Obtain the TMR memory area for SEV-ES use */
> -	tmr_page = alloc_pages(GFP_KERNEL, get_order(SEV_ES_TMR_SIZE));
> -	if (tmr_page) {
> -		sev_es_tmr = page_address(tmr_page);
> -	} else {
> -		sev_es_tmr = NULL;
> +	sev_es_tmr = sev_fw_alloc(SEV_ES_TMR_SIZE);
> +	if (!sev_es_tmr)
>   		dev_warn(sev->dev,
>   			 "SEV: TMR allocation failed, SEV-ES support unavailable\n");
> -	}
>   
>   	/* Initialize the platform */
>   	rc = sev_platform_init(&error);
>