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Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug
From: |
Gleb Natapov |
Subject: |
Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug |
Date: |
Tue, 24 Apr 2012 11:34:32 +0300 |
On Tue, Apr 24, 2012 at 10:24:51AM +0200, Vasilis Liaskovitis wrote:
> Hi,
> On Tue, Apr 24, 2012 at 10:52:24AM +0300, Gleb Natapov wrote:
> > On Mon, Apr 23, 2012 at 02:31:15PM +0200, Vasilis Liaskovitis wrote:
> > > The 440fx spec mentions: "The address range from the top of main DRAM to 4
> > > Gbytes (top of physical memory space supported by the 440FX PCIset) is
> > > normally
> > > mapped to PCI. The PMC forwards all accesses within this address range to
> > > PCI."
> > >
> > > What we probably want is that the initial memory map creation takes into
> > > account
> > > all dimms specified (both populated/unpopulated)
> > Yes.
> >
> > > So "-m 1G, -device dimm,size=1G,populated=true -device
> > > dimm,size=1G,populated=false"
> > > would create a system map with top of memory and start of PCI-hole at 2G.
> > >
> > What -m 1G means on this command line? Isn't it redundant?
> yes, this was redundant with the original concept.
>
> > May be we should make -m create non unplaggable, populated slot starting
> > at address 0. Ten you config above will specify 3G memory with 2G
> > populated (first of which is not removable) and 1G unpopulated. PCI hole
> > starts above 3G.
>
> I agree -m should mean one big unpluggable slot.
>
> So in the new proposal,"-device dimm populated=true" means a hot-removable
> dimm
> that has already been hotplugged.
>
Yes.
> A question here is when exactly should the initial hot-add event for this dimm
> be played? If the relevant OSPM has not yet been initialized (e.g.
> acpi_memhotplug
> module in a linux guest needs to be loaded), the guest may not see the event.
> This is a general issue of course, but with initially populated hot-removable
> dimms it may be a bigger issue. Can ospm acpi initialization be detected?
>
> Or maybe you are suggesting "populated=true" is part of initial memory (i.e.
> not
> hot-added, but still hot-removable). Though in that case guestOS may use it
> for
> bootmem allocations, making hot-remove more likely to fail at the memory
> offlining stage.
>
If memory slot is populated even before OSPM is started BIOS will detect
that by reading mem_sts and will create e820 map appropriately. OSPM
will detect it by evaluating _STA during boot. This is not unique for
memory hot-plug. Any hotpluggable device have the same issue.
--
Gleb.
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, (continued)
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Vasilis Liaskovitis, 2012/04/20
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Gleb Natapov, 2012/04/22
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Avi Kivity, 2012/04/22
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Gleb Natapov, 2012/04/22
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Avi Kivity, 2012/04/22
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Gleb Natapov, 2012/04/22
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Vasilis Liaskovitis, 2012/04/23
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Gleb Natapov, 2012/04/24
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Vasilis Liaskovitis, 2012/04/24
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug,
Gleb Natapov <=
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Avi Kivity, 2012/04/23
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Gleb Natapov, 2012/04/24
- Re: [Qemu-devel] [RFC PATCH 0/9] ACPI memory hotplug, Avi Kivity, 2012/04/24