From: David Hildenbrand <david@redhat.com>
To: mhklinux@outlook.com, haiyangz@microsoft.com, wei.liu@kernel.org,
decui@microsoft.com, linux-kernel@vger.kernel.org,
linux-hyperv@vger.kernel.org
Subject: Re: [PATCH 1/1] hv_balloon: Enable hot-add for memblock sizes > 128 Mbytes
Date: Fri, 26 Apr 2024 10:58:56 +0200 [thread overview]
Message-ID: <30d66f75-60c8-4ebf-8451-839806400dd4@redhat.com> (raw)
In-Reply-To: <20240311181238.1241-1-mhklinux@outlook.com>
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
next prev parent reply other threads:[~2024-04-26 8:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-11 18:12 [PATCH 1/1] hv_balloon: Enable hot-add for memblock sizes > 128 Mbytes mhkelley58
2024-04-25 14:31 ` Michael Kelley
2024-04-26 8:58 ` David Hildenbrand [this message]
2024-04-26 16:35 ` Michael Kelley
2024-04-29 15:30 ` Michael Kelley
2024-04-30 8:52 ` David Hildenbrand
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