linux-kernel - Re: [PATCH v2 4/9] crypto: ccp: Register SNP panic notifier only if SNP is enabled

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Message-ID: <912eb75b-f756-4c9e-af66-225412f69488@amd.com>
Date: Fri, 27 Dec 2024 20:13:29 +1100
From: Alexey Kardashevskiy <aik@....com>
To: Ashish Kalra <Ashish.Kalra@....com>, seanjc@...gle.com,
 pbonzini@...hat.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
 thomas.lendacky@....com, john.allen@....com, herbert@...dor.apana.org.au,
 davem@...emloft.net
Cc: michael.roth@....com, dionnaglaze@...gle.com, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
 linux-coco@...ts.linux.dev
Subject: Re: [PATCH v2 4/9] crypto: ccp: Register SNP panic notifier only if
 SNP is enabled

On 17/12/24 10:58, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@....com>
> 
> Register the SNP panic notifier if and only if SNP is actually
> initialized and deregistering the notifier when shutting down
> SNP in PSP driver when KVM module is unloaded.
> 
> Currently the SNP panic notifier is being registered
> irrespective of SNP being enabled/initialized and with this
> change the SNP panic notifier is registered only if SNP
> support is enabled and initialized.
> 
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
>   drivers/crypto/ccp/sev-dev.c | 21 +++++++++++++--------
>   1 file changed, 13 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 9632a9a5c92e..7c15dec55f58 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -109,6 +109,13 @@ static void *sev_init_ex_buffer;
>    */
>   static struct sev_data_range_list *snp_range_list;
>   
> +static int snp_shutdown_on_panic(struct notifier_block *nb,
> +				 unsigned long reason, void *arg);
> +
> +static struct notifier_block snp_panic_notifier = {
> +	.notifier_call = snp_shutdown_on_panic,
> +};
> +

A nit: I'd probably move the hunk right before __sev_snp_init_locked(). 
And the body of snp_shutdown_on_panic(), just to keep SNP code together. 
Not sure about the result though so feel free to ignore :)


>   static inline bool sev_version_greater_or_equal(u8 maj, u8 min)
>   {
>   	struct sev_device *sev = psp_master->sev_data;
> @@ -1191,6 +1198,9 @@ static int __sev_snp_init_locked(int *error)
>   	dev_info(sev->dev, "SEV-SNP API:%d.%d build:%d\n", sev->api_major,
>   		 sev->api_minor, sev->build);
>   
> +	atomic_notifier_chain_register(&panic_notifier_list,
> +				       &snp_panic_notifier);
> +
>   	sev_es_tmr_size = SNP_TMR_SIZE;
>   
>   	return 0;
> @@ -1751,6 +1761,9 @@ static int __sev_snp_shutdown_locked(int *error, bool panic)
>   	sev->snp_initialized = false;
>   	dev_dbg(sev->dev, "SEV-SNP firmware shutdown\n");
>   
> +	atomic_notifier_chain_unregister(&panic_notifier_list,
> +					 &snp_panic_notifier);
> +
>   	/* Reset TMR size back to default */
>   	sev_es_tmr_size = SEV_TMR_SIZE;
>   
> @@ -2490,10 +2503,6 @@ static int snp_shutdown_on_panic(struct notifier_block *nb,
>   	return NOTIFY_DONE;
>   }
>   
> -static struct notifier_block snp_panic_notifier = {
> -	.notifier_call = snp_shutdown_on_panic,
> -};
> -
>   int sev_issue_cmd_external_user(struct file *filep, unsigned int cmd,
>   				void *data, int *error)
>   {
> @@ -2542,8 +2551,6 @@ void sev_pci_init(void)
>   	dev_info(sev->dev, "SEV%s API:%d.%d build:%d\n", sev->snp_initialized ?
>   		"-SNP" : "", sev->api_major, sev->api_minor, sev->build);
>   
> -	atomic_notifier_chain_register(&panic_notifier_list,
> -				       &snp_panic_notifier);
>   	return;
>   
>   err:
> @@ -2561,6 +2568,4 @@ void sev_pci_exit(void)
>   
>   	sev_firmware_shutdown(sev);
>   

can remove the above empty line too. Otherwise

Reviewed-by: Alexey Kardashevskiy <aik@....com>


> -	atomic_notifier_chain_unregister(&panic_notifier_list,
> -					 &snp_panic_notifier);
>   }

-- 
Alexey