linux-kernel - Re: [PATCH 1/1] powerpc/kernel: Enables memory hot-remove after reboot on pseries guests

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Message-ID: <a93a42c672171ed93557f9f9f3b5d64013980f26.camel@linux.ibm.com>
Date:   Wed, 04 Mar 2020 19:05:43 -0300
From:   Leonardo Bras <leonardo@...ux.ibm.com>
To:     Bharata B Rao <bharata.rao@...il.com>
Cc:     ndfont@...il.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        arbab@...ux.ibm.com, Claudio Carvalho <cclaudio@...ux.ibm.com>,
        Michael Roth <mdroth@...ux.vnet.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Hari Bathini <hbathini@...ux.ibm.com>
Subject: Re: [PATCH 1/1] powerpc/kernel: Enables memory hot-remove after
 reboot on pseries guests

On Wed, 2020-03-04 at 04:18 -0300, Leonardo Bras wrote:
> Humm, this makes sense.
> But with mu change, these pieces of memory only get into ZONE_MOVABLE
> if the boot parameter 'movable_node' gets passed to guest kernel. 

Humm, I think your patch also does that.

> So, even if we are unable to sort out some flag combination that work
> fine for both use-cases, if PowerVM don't pass 'movable_node' as boot
> parameter to kernel, it will behave just as today.

Also, another option would be adding a new 'removable' flag, given it
has a lot of free bytes. It would only be passed by qemu, so we would
be safe with PowerVM. 

Then we would have 
+	if(lmb->flags & DRCONF_MEM_REMOVABLE)	
+		early_init_dt_mark_hotplug_memory_arch(base, size);

Do you know if it's possible?
We would need to update the LOPAPR? 

Leonardo

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