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SubjectRe: [PATCH v5 5/5] x86/kvm: Avoid dynamic allocation of pvclock data when SEV is active
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On 09/06/2018 08:50 AM, Sean Christopherson wrote:
...

>>
>> So are we going to be defining a decrypted section for every piece of
>> machinery now?
>>
>> That's a bit too much in my book.
>>
>> Why can't you simply free everything in .data..decrypted on !SVE guests?
>
> That would prevent adding __decrypted to existing declarations, e.g.
> hv_clock_boot, which would be ugly in its own right. A more generic
> solution would be to add something like __decrypted_exclusive to mark
> data that is used if and only if SEV is active, and then free the
> SEV-only data when SEV is disabled.
>
> Originally, my thought was that this would be a one-off case and the
> array could be freed directly in kvmclock_init(), e.g.:
>


Please note that kvmclock_init() is called very early during the boot
process. We will not be able to use free_init_pages(...) so early.
Additionally, we also need to consider the bare-metal case -- which
will never call the kvmclock_init().



> static struct pvclock_vsyscall_time_info
> hv_clock_aux[HVC_AUX_ARRAY_SIZE] __decrypted __aligned(PAGE_SIZE);
>
> ...
>
> void __init kvmclock_init(void)
> {
> u8 flags;
>
> if (!sev_active())
> free_init_pages("unused decrypted",
> (unsigned long)hv_clock_aux,
> (unsigned long)hv_clock_aux + sizeof(hv_clock_aux));
>
>>

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