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

Tianyu Lan
2023-06-07T08:16:40Z

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@redhat.com/
So I think it's unnessary to encrypt the mem again here.