Re: [PATCH 4/9] drivers: hv: Mark shared pages unencrypted in SEV-SNP enlightened guest

[Tianyu Lan]

On 6/5/2023 8:54 PM, Vitaly Kuznetsov wrote:
> > @@ -402,7 +417,14 @@ int hv_common_cpu_die(unsigned int cpu)
> >   
> >   	local_irq_restore(flags);
> >   
> > -	kfree(mem);
> > +	if (hv_isolation_type_en_snp()) {
> > +		ret = set_memory_encrypted((unsigned long)mem, pgcount);
> > +		if (ret)
> > +			pr_warn("Hyper-V: Failed to encrypt input arg on cpu%d: %d\n",
> > +				cpu, ret);
> > +		/* It's unsafe to free 'mem'. */
> > +		return 0;
> Why is it unsafe to free 'mem' if ret == 0? Also, why don't we want to
> proparate non-zero 'ret' from here to fail CPU offlining?

Based on Michael's patch the mem will not be freed during cpu offline.
https://lwn.net/ml/linux-kernel/87cz2j5zrc.fsf@xxxxxxxxxx/
So I think it's unnessary to encrypt the mem again here.