Re: [PATCH 2/2] virtio: replace arch_has_restricted_virtio_memory_access()

Juergen Gross
2022-04-27T06:40:16Z

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On 26.04.22 21:51, Heiko Carstens wrote:
> On Tue, Apr 26, 2022 at 07:35:43PM +0200, Borislav Petkov wrote:
>> On Tue, Apr 26, 2022 at 03:40:21PM +0200, Juergen Gross wrote:
>>> /* protected virtualization */
>>> static void pv_init(void)
>>> {
>>> if (!is_prot_virt_guest())
>>> return;
>>>
>>> + platform_set_feature(PLATFORM_VIRTIO_RESTRICTED_MEM_ACCESS);
>>
>> Kinda long-ish for my taste. I'll probably call it:
>>
>> platform_set()
>>
>> as it is implicit that it sets a feature bit.
>
> ...and platform_clear(), instead of platform_reset_feature() please.

Fine with me.

>
>> In any case, yeah, looks ok at a quick glance. It would obviously need
>> for more people to look at it and say whether it makes sense to them and
>> whether that's fine to have in generic code but so far, the experience
>> with cc_platform_* says that it seems to work ok in generic code.
>
> We _could_ convert s390's machine flags to this mechanism. Those flags
> are historically per-cpu, but if I'm not mistaken none of them is
> performance critical anymore, and those who are could/should probably
> transformed to jump labels or alternatives anyway.

I was planning to look at the x86 cpu features to see whether some of
those might be candidates to be switched to platform features instead.

Juergen

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