Re: [Part2 PATCH v6 13/38] crypto: ccp: Add Secure Encrypted Virtualization (SEV) command support

[Brijesh Singh]

On 10/23/2017 04:20 AM, Borislav Petkov wrote:
> On Thu, Oct 19, 2017 at 09:33:48PM -0500, Brijesh Singh wrote:
> > +static int __sev_platform_init(struct sev_data_init *data, int *error)
> > +{
> > +	int rc = 0;
> > +
> > +	mutex_lock(&fw_init_mutex);
> > +
> > +	if (!fw_init_count) {
>
> I still don't like global semaphores. Can you get the status and check
> for PSTATE.INIT state and do the init only if the platform is in
> PSTATE.UNINIT?


Calling PLATFORM_GET_STATUS is not required, we can manage the state 
through a simple ref count variable. Issuing PSP commands will always be 
much more expensive compare to accessing a protected global variable. I 
would prefer to avoid invoking PSP command if possible. Additionally, 
the global semaphore is still needed to serialize the 
sev_platform_init() and sev_platform_shutdown() from multiple processes. 
e.g If process "A" calls sev_platform_init() and if it gets preempted 
due to whatever reason then we don't want another process to issue the 
shutdown command while process "A" is in middle of sev_platform_init().

-Brijesh