Messages in this thread | | | Date | Tue, 30 Apr 2024 10:52:50 +0200 | Subject | Re: [PATCH 1/1] hv_balloon: Enable hot-add for memblock sizes > 128 Mbytes | From | David Hildenbrand <> |
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On 29.04.24 17:30, Michael Kelley wrote: > From: Michael Kelley <mhklinux@outlook.com> Sent: Friday, April 26, 2024 9:36 AM >>>> @@ -505,8 +505,9 @@ enum hv_dm_state { >>>> >>>> static __u8 recv_buffer[HV_HYP_PAGE_SIZE]; >>>> static __u8 balloon_up_send_buffer[HV_HYP_PAGE_SIZE]; >>>> +static unsigned long ha_chunk_pgs; >>> >>> Why not stick to PAGES_IN_2M and call this >>> >>> ha_pages_in_chunk? Much easier to get than "pgs". >> >> OK. I was trying to keep the new identifier short so that >> mechanically substituting it for HA_CHUNK didn't blow up >> the line length. >> >>> >>> Apart from that looks good. Some helper macros to convert size to chunks >>> etc. might make the code even more readable. >> >> I'll look at this. Might help the line length problem too. >> > > I didn't see any particular complexity in converting size to chunks. But > this slightly opaque sequence is repeated in three places: > > new_inc = (residual / HA_CHUNK) * HA_CHUNK; > if (residual % HA_CHUNK) > new_inc += HA_CHUNK; > > If HA_CHUNK (or the new memblock size based variable) is a > power of 2, then these can become: > > new_inc = ALIGN(residual, HA_CHUNK); > > which is a lot better. I'll make that change, and a couple of other > changes where things are open coded that could be existing > kernel macros.
Cool! Make sure to CC me on v2.
> > Question: Is memblock size guaranteed to be a power of 2? It looks > to be so in the x86 code, but I can't tell on s390 and ppc. For safety, > I'll add a check in the Hyper-V balloon driver init code, as the > communication with Hyper-V expects a power of 2.
Yes, in memory_dev_init() we make sure that the size is a power of 2, and if it is not, we would panic().
-- Cheers,
David / dhildenb
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