Messages in this thread | | | Date | Fri, 26 Apr 2024 10:58:56 +0200 | Subject | Re: [PATCH 1/1] hv_balloon: Enable hot-add for memblock sizes > 128 Mbytes | From | David Hildenbrand <> |
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On 11.03.24 19:12, mhkelley58@gmail.com wrote: > From: Michael Kelley <mhklinux@outlook.com> > > The Hyper-V balloon driver supports hot-add of memory in addition > to ballooning. Current code hot-adds in fixed size chunks of > 128 Mbytes (fixed constant HA_CHUNK in the code). While this works > in Hyper-V VMs with 64 Gbytes or less or memory where the Linux > memblock size is 128 Mbytes, the hot-add fails for larger memblock > sizes because add_memory() expects memory to be added in chunks > that match the memblock size. Messages like the following are > reported when Linux has a 256 Mbyte memblock size: > > [ 312.668859] Block size [0x10000000] unaligned hotplug range: > start 0x310000000, size 0x8000000 > [ 312.668880] hv_balloon: hot_add memory failed error is -22 > [ 312.668984] hv_balloon: Memory hot add failed > > Larger memblock sizes are usually used in VMs with more than > 64 Gbytes of memory, depending on the alignment of the VM's > physical address space.
Right, that's the case since 2018.
> > Fix this problem by having the Hyper-V balloon driver determine > the Linux memblock size, and process hot-add requests in that > chunk size instead of a fixed 128 Mbytes. Also update the hot-add > alignment requested of the Hyper-V host to match the memblock > size instead of being a fixed 128 Mbytes.
That way, we should never be getting unaligned ranges IIRC, correct? I think we added ways in QEMU to guarantee that for the HV-balloon implementation as well.
> > The code changes look significant, but in fact are just a
Nah, it's okay :)
> simple text substitution of a new global variable for the > previous HA_CHUNK constant. No algorithms are changed except > to initialize the new global variable and to calculate the > alignment value to pass to Hyper-V. Testing with memblock > sizes of 256 Mbytes and 2 Gbytes shows correct operation. > > Signed-off-by: Michael Kelley <mhklinux@outlook.com> > --- > drivers/hv/hv_balloon.c | 64 ++++++++++++++++++++++++----------------- > 1 file changed, 37 insertions(+), 27 deletions(-) > > diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c > index e000fa3b9f97..d3bfbf3d274a 100644 > --- a/drivers/hv/hv_balloon.c > +++ b/drivers/hv/hv_balloon.c > @@ -425,11 +425,11 @@ struct dm_info_msg { > * The range start_pfn : end_pfn specifies the range > * that the host has asked us to hot add. The range > * start_pfn : ha_end_pfn specifies the range that we have > - * currently hot added. We hot add in multiples of 128M > - * chunks; it is possible that we may not be able to bring > - * online all the pages in the region. The range > + * currently hot added. We hot add in chunks equal to the > + * memory block size; it is possible that we may not be able > + * to bring online all the pages in the region. The range > * covered_start_pfn:covered_end_pfn defines the pages that can > - * be brough online. > + * be brought online. > */ > > struct hv_hotadd_state { > @@ -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".
Apart from that looks good. Some helper macros to convert size to chunks etc. might make the code even more readable.
-- Cheers,
David / dhildenb
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