While providing guests, it's desirable to resize it's memory on demand.
By now, it's possible to do so by creating a guest with a small base
memory, hot-plugging all the rest, and using 'movable_node' kernel
command-line parameter, which puts all hot-plugged memory in
ZONE_MOVABLE, allowing it to be removed whenever needed.
But there is an issue regarding guest reboot:
If memory is hot-plugged, and then the guest is rebooted, all hot-plugged
memory goes to ZONE_NORMAL, which offers no guaranteed hot-removal.
It usually prevents this memory to be hot-removed from the guest.
It's possible to use device-tree information to fix that behavior, as
it stores flags for LMB ranges on ibm,dynamic-memory-vN.
It involves marking each memblock with the correct flags as hotpluggable
memory, which mm/memblock.c puts in ZONE_MOVABLE during boot if
'movable_node' is passed.
For carrying such information, the new flag DRCONF_MEM_HOTPLUGGED is
proposed, which should be true if memory was hot-plugged on guest, and
false if it's base memory.
During boot, guest kernel reads the device-tree, early_init_drmem_lmb()
is called for every added LMBs. Here, checking for this new flag and
marking memblocks as hotplugable memory is enough to get the desirable
behavior.
This should cause no change if 'movable_node' parameter is not passed
in kernel command-line.
Signed-off-by: Leonardo Bras <[email protected]>
---
The new flag was already proposed on Power Architecture documentation,
and it's waiting for approval.
I would like to get your comments on this change, but it's still not
ready for being merged.
I will send the matching qemu change as a reply later.
Changes since v1:
- Adds new flag, so PowerVM is compatible with the change.
- Fixes mistakes in code
---
arch/powerpc/include/asm/drmem.h | 1 +
arch/powerpc/kernel/prom.c | 9 +++++++--
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/drmem.h b/arch/powerpc/include/asm/drmem.h
index 3d76e1c388c2..92083b4565f6 100644
--- a/arch/powerpc/include/asm/drmem.h
+++ b/arch/powerpc/include/asm/drmem.h
@@ -65,6 +65,7 @@ struct of_drconf_cell_v2 {
#define DRCONF_MEM_ASSIGNED 0x00000008
#define DRCONF_MEM_AI_INVALID 0x00000040
#define DRCONF_MEM_RESERVED 0x00000080
+#define DRCONF_MEM_HOTPLUGGED 0x00000100
static inline u32 drmem_lmb_size(void)
{
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 6620f37abe73..9c5cb2e8049e 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -515,9 +515,14 @@ static void __init early_init_drmem_lmb(struct drmem_lmb *lmb,
size = 0x80000000ul - base;
}
+ if (!validate_mem_limit(base, &size))
+ continue;
+
DBG("Adding: %llx -> %llx\n", base, size);
- if (validate_mem_limit(base, &size))
- memblock_add(base, size);
+ memblock_add(base, size);
+
+ if (lmb->flags & DRCONF_MEM_HOTPLUGGED)
+ memblock_mark_hotplug(base, size);
} while (--rngs);
}
#endif /* CONFIG_PPC_PSERIES */
--
2.24.1
On Thu, 2020-03-05 at 20:32 -0300, Leonardo Bras wrote:
> I will send the matching qemu change as a reply later.
http://patchwork.ozlabs.org/patch/1249931/
On Thu, 2020-03-05 at 20:32 -0300, Leonardo Bras wrote:
> ---
> The new flag was already proposed on Power Architecture documentation,
> and it's waiting for approval.
>
> I would like to get your comments on this change, but it's still not
> ready for being merged.
New flag got approved on the documentation.
Please review this patch.
On Wed, Apr 1, 2020 at 8:38 PM Leonardo Bras <[email protected]> wrote:
>
> On Thu, 2020-03-05 at 20:32 -0300, Leonardo Bras wrote:
> > ---
> > The new flag was already proposed on Power Architecture documentation,
> > and it's waiting for approval.
> >
> > I would like to get your comments on this change, but it's still not
> > ready for being merged.
>
> New flag got approved on the documentation.
> Please review this patch.
Looks good to me, also tested with PowerKVM guests.
Reviewed-by: Bharata B Rao <[email protected]>
Regards,
Bharata.
--
http://raobharata.wordpress.com/
Hello Bharata, thank you for reviewing and testing!
During review of this new flag, it was suggested to change it's name to
a better one (on platform's viewpoint).
So I will have to change the flag name from DRCONF_MEM_HOTPLUGGED to
DRCONF_MEM_HOTREMOVABLE.
Everything should work the same as today.
Best regards,
Leonardo
On Thu, 2020-04-02 at 14:44 +0530, Bharata B Rao wrote:
> Looks good to me, also tested with PowerKVM guests.
>
> Reviewed-by: Bharata B Rao <[email protected]>
>
> Regards,
> Bharata.