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Date: Tue, 20 Jul 2010 13:34:42 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Daniel Kiper <dkiper@...-space.pl>
Cc: jeremy@...p.org, xen-devel@...ts.xensource.com,
linux-kernel@...r.kernel.org
Subject: Re: [Xen-devel] [PATCH] GSoC 2010 - Memory hotplug support for Xen
guests - patch for review only
On Fri, Jul 16, 2010 at 04:20:37PM +0200, Daniel Kiper wrote:
> Hello,
>
> As I promised I am sending first patch which enables
> memory hotplug in Xen guests. It is version for review
> only. It has been tested on Xen Ver 4.0.0 in PV guest x86_64
> with Linux kernel Ver. 2.6.32.16. In general it works,
> however... For details look below...
>
> This patch enables two modes of operation:
> - enabled by CONFIG_XEN_MEMORY_HOTPLUG config option:
> - set memory limit for chosen domU from dom0:
> xm mem-max <domU> <new_memory_size_limit>
> - add memory in chosen domU: echo <unused_address> > \
> /sys/devices/system/memory/probe
This being the physical addresses. What happens if I pick
ones at random intervals. Say I've got 2GB in the domain,
and I give it 6GB, but the value I provide to to the "probe" is
1048576 (4GB>>12). Would that mean I get the 2GB, and then later
if I did "echo 524288 > probe" it would fill out the 2GB hole?
> - online memory in chosen domU: echo online > \
> /sys/devices/system/memory/memory<section_number>/state
> - enabled by CONFIG_XEN_BALLOON_MEMORY_HOTPLUG config option:
> - set memory limit for chosen domU from dom0:
> xm mem-max <domU> <new_memory_size_limit>
> - add memory for chosen domU from dom0:
> xm mem-set <domU> <new_memory_size>
>
> TODO:
> - there is bug which generate oops when memory
> is added and removed a few times from domU
> (CONFIG_XEN_BALLOON_MEMORY_HOTPLUG); probably
> I missed something,
> - there is no synchronization between CONFIG_XEN_MEMORY_HOTPLUG
> and CONFIG_XEN_BALLOON_MEMORY_HOTPLUG yet; memory
> added from domU is not added to balloon_stats,
> - some additional error checking should be implemented,
> - final patch will be available for Linux kernel
> Ver. 2.6.32.y, latest stable and RC,
> - tests on all planned platforms.
>
> I am waiting for your comments.
Here are some.. Hadn't done a complete review.
>
> Daniel
>
> diff -Nru linux-2.6.32.16.orig/drivers/base/memory.c linux-2.6.32.16/drivers/base/memory.c
> --- linux-2.6.32.16.orig/drivers/base/memory.c 2010-07-05 20:14:00.000000000 +0200
> +++ linux-2.6.32.16/drivers/base/memory.c 2010-07-16 11:48:45.000000000 +0200
> @@ -3,6 +3,7 @@
> *
> * Written by Matt Tolentino <matthew.e.tolentino@...el.com>
> * Dave Hansen <haveblue@...ibm.com>
> + * Daniel Kiper <dkiper@...-space.pl>
> *
> * This file provides the necessary infrastructure to represent
> * a SPARSEMEM-memory-model system's physical memory in /sysfs.
> @@ -26,6 +27,16 @@
> #include <asm/atomic.h>
> #include <asm/uaccess.h>
>
> +#ifdef CONFIG_XEN_MEMORY_HOTPLUG
> +#include <linux/vmalloc.h>
> +#include <asm/xen/hypervisor.h>
> +#include <asm/xen/hypercall.h>
> +#include <xen/interface/xen.h>
> +#include <xen/interface/memory.h>
> +#include <xen/features.h>
> +#include <xen/page.h>
> +#endif
> +
> #define MEMORY_CLASS_NAME "memory"
>
> static struct sysdev_class memory_sysdev_class = {
> @@ -314,13 +325,61 @@
> memory_probe_store(struct class *class, const char *buf, size_t count)
> {
> u64 phys_addr;
> - int nid;
> - int ret;
> + long ret;
> +
> +#ifdef CONFIG_XEN_MEMORY_HOTPLUG
> + struct xen_memory_reservation reservation = {
> + .address_bits = 0,
> + .extent_order = 0,
> + .domid = DOMID_SELF,
> + .nr_extents = PAGES_PER_SECTION
> + };
> + unsigned long *frame_list, i, nr_pages, pfn;
> +#endif
>
> phys_addr = simple_strtoull(buf, NULL, 0);
>
> - nid = memory_add_physaddr_to_nid(phys_addr);
> - ret = add_memory(nid, phys_addr, PAGES_PER_SECTION << PAGE_SHIFT);
> +#ifdef CONFIG_XEN_MEMORY_HOTPLUG
> + if (xen_domain()) {
> + if (!(frame_list = vmalloc(PAGES_PER_SECTION * sizeof(unsigned long)))) {
> + printk(KERN_ERR "%s: vmalloc: Out of memory\n", __func__);
> + return -ENOMEM;
> + }
> +
> + set_xen_guest_handle(reservation.extent_start, frame_list);
> + for (i = 0, pfn = phys_addr >> PAGE_SHIFT; i < PAGES_PER_SECTION; ++i, ++pfn)
> + frame_list[i] = pfn;
> +
> + ret = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
> +
> + if (ret < PAGES_PER_SECTION) {
> + if (ret > 0) {
> + printk(KERN_ERR "%s: PHYSMAP is not fully populated: %li/%lu\n",
> + __func__, ret, PAGES_PER_SECTION);
> + reservation.nr_extents = nr_pages = ret;
> + ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
> + BUG_ON(ret != nr_pages);
> + ret = -ENOMEM;
> + } else {
> + ret = (ret < 0) ? ret : -ENOMEM;
> + printk(KERN_ERR "%s: Can't populate PHYSMAP: %li\n", __func__, ret);
> + }
> + vfree(frame_list);
> + return ret;
> + }
> +
> + for (i = 0, pfn = phys_addr >> PAGE_SHIFT; i < PAGES_PER_SECTION; ++i, ++pfn) {
> + BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
> + phys_to_machine_mapping_valid(pfn));
> + set_phys_to_machine(pfn, frame_list[i]);
> + }
> +
> + vfree(frame_list);
All of this looks to be a great candidate for sticking it in
its own file. Say drivers/xen/mem_hotplug.c. And then in a header
(include/xen/mem_hotplug.h) have something akin to this:
#if defined(XEN_BALLOON_MEMORY_HOTPLUG)
int xen_add_memory(u64 phys_addr);
#else
static int xen_add_memory(u64 phys_addr) { return -1; }
#endif
And the patch for drivers/base/memory.c can include:
.. <snip>..
#include <xen/mem_hotplug.h>
...
nid = memory_add_physaddr_to_nid(phys_addr);
if (xen_domain())
ret = xen_add_memory(phys_addr);
else
ret = add_memory(nid, phys_addr, PAGES_PER_SECTION << PAGE_SHIFT);
> + }
> +#endif
> +
> + ret = add_memory(memory_add_physaddr_to_nid(phys_addr),
> + phys_addr, PAGES_PER_SECTION << PAGE_SHIFT);
No need to rewrite that. Use the old implementation for the getting 'nid'.
>
> if (ret)
> count = ret;
> diff -Nru linux-2.6.32.16.orig/drivers/xen/Kconfig linux-2.6.32.16/drivers/xen/Kconfig
> --- linux-2.6.32.16.orig/drivers/xen/Kconfig 2010-07-05 20:14:00.000000000 +0200
> +++ linux-2.6.32.16/drivers/xen/Kconfig 2010-07-09 21:04:17.000000000 +0200
> @@ -7,6 +7,16 @@
> the system to expand the domain's memory allocation, or alternatively
> return unneeded memory to the system.
>
> +config XEN_BALLOON_MEMORY_HOTPLUG
> + bool "Xen memory balloon driver with memory hotplug support"
> + depends on EXPERIMENTAL && XEN && XEN_BALLOON && MEMORY_HOTPLUG
> + default n
> + help
> + Xen memory balloon driver with memory hotplug support allows expanding
> + memory available for the system above limit declared at system startup.
> + It is very useful on critical systems which require long run without
> + rebooting.
> +
> config XEN_SCRUB_PAGES
> bool "Scrub pages before returning them to system"
> depends on XEN_BALLOON
> @@ -60,4 +70,4 @@
> Create entries under /sys/hypervisor describing the Xen
> hypervisor environment. When running native or in another
> virtual environment, /sys/hypervisor will still be present,
> - but will have no xen contents.
> \ No newline at end of file
> + but will have no xen contents.
> diff -Nru linux-2.6.32.16.orig/drivers/xen/balloon.c linux-2.6.32.16/drivers/xen/balloon.c
> --- linux-2.6.32.16.orig/drivers/xen/balloon.c 2010-07-05 20:14:00.000000000 +0200
> +++ linux-2.6.32.16/drivers/xen/balloon.c 2010-07-16 15:06:53.000000000 +0200
> @@ -6,6 +6,7 @@
> * Copyright (c) 2003, B Dragovic
> * Copyright (c) 2003-2004, M Williamson, K Fraser
> * Copyright (c) 2005 Dan M. Smith, IBM Corporation
> + * Copyright (c) 2010 Daniel Kiper
> *
> * This program is free software; you can redistribute it and/or
> * modify it under the terms of the GNU General Public License version 2
> @@ -74,6 +75,10 @@
> /* Number of pages in high- and low-memory balloons. */
> unsigned long balloon_low;
> unsigned long balloon_high;
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + u64 hotplug_start_addr;
> + u64 hotplug_size;
> +#endif
> };
>
> static DEFINE_MUTEX(balloon_mutex);
> @@ -183,6 +188,9 @@
>
> static unsigned long current_target(void)
> {
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + return balloon_stats.target_pages;
> +#else
> unsigned long target = balloon_stats.target_pages;
>
> target = min(target,
> @@ -191,6 +199,7 @@
> balloon_stats.balloon_high);
>
> return target;
> +#endif
> }
>
> static int increase_reservation(unsigned long nr_pages)
> @@ -204,17 +213,48 @@
> .domid = DOMID_SELF
> };
>
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + struct resource *r;
> +#endif
> +
> if (nr_pages > ARRAY_SIZE(frame_list))
> nr_pages = ARRAY_SIZE(frame_list);
>
> spin_lock_irqsave(&balloon_lock, flags);
>
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
> + if (!balloon_stats.hotplug_start_addr)
Can you put a comment explainig what this is doing?
> + for (r = iomem_resource.child; r; r = r->sibling)
> + if (!r->sibling || r->sibling->start >
> + (((r->end >> PAGE_SHIFT) + balloon_stats.target_pages -
> + balloon_stats.current_pages) << PAGE_SHIFT)) {
> + balloon_stats.hotplug_start_addr = (((r->end >> PAGE_SHIFT) + 1) << PAGE_SHIFT);
> + break;
> + }
> +
> + pfn = (balloon_stats.hotplug_start_addr + balloon_stats.hotplug_size) >> PAGE_SHIFT;
> +
> + for (i = 0; i < nr_pages; ++i, ++pfn)
> + frame_list[i] = pfn;
> +
> + pfn -= nr_pages + 1;
Can you make these two:
> + } else {
> + page = balloon_first_page();
> + for (i = 0; i < nr_pages; i++) {
> + BUG_ON(page == NULL);
> + frame_list[i] = page_to_pfn(page);
> + page = balloon_next_page(page);
> + }
> + }
> +#else
> page = balloon_first_page();
> for (i = 0; i < nr_pages; i++) {
> BUG_ON(page == NULL);
> frame_list[i] = page_to_pfn(page);
> page = balloon_next_page(page);
> }
"else" statement collapse in one? One way would be for you to say have:
#if defined(CONFIG_XEN_BALLOON_MEMORY_HOTPLUG)
#define xen_check_hotplug 1
#else
#define xen_check_hotplug 0
#endif
And use that in the above, to say: if (xen_check_hotplug &&
!balloon_stats.balloon_low && !balloon_stats.balloon_high ...) {
// some code
} else {
// original ballion code.
> +#endif
>
> set_xen_guest_handle(reservation.extent_start, frame_list);
> reservation.nr_extents = nr_pages;
> @@ -223,15 +263,30 @@
> goto out;
>
> for (i = 0; i < rc; i++) {
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + if (balloon_stats.hotplug_start_addr)
> + ++pfn;
> + else {
> + page = balloon_retrieve();
> + BUG_ON(page == NULL);
> + pfn = page_to_pfn(page);
> + }
> +#else
> page = balloon_retrieve();
> BUG_ON(page == NULL);
> -
> pfn = page_to_pfn(page);
> +#endif
> +
> BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
> phys_to_machine_mapping_valid(pfn));
>
> set_phys_to_machine(pfn, frame_list[i]);
>
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + if (balloon_stats.hotplug_start_addr)
> + continue;
> +#endif
> +
> /* Link back into the page tables if not highmem. */
> if (pfn < max_low_pfn) {
> int ret;
> @@ -248,6 +303,11 @@
> __free_page(page);
> }
>
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + if (balloon_stats.hotplug_start_addr)
> + balloon_stats.hotplug_size += rc << PAGE_SHIFT;
> +#endif
> +
> balloon_stats.current_pages += rc;
>
> out:
> @@ -344,8 +404,24 @@
> } while ((credit != 0) && !need_sleep);
>
> /* Schedule more work if there is some still to be done. */
> +
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> if (current_target() != balloon_stats.current_pages)
> mod_timer(&balloon_timer, jiffies + HZ);
> + else
> + if (balloon_stats.hotplug_start_addr) {
> + /* TODO: deallocate memory if something goes wrong !!! */
> + add_memory(memory_add_physaddr_to_nid(balloon_stats.hotplug_start_addr),
> + balloon_stats.hotplug_start_addr, balloon_stats.hotplug_size);
> + online_pages(balloon_stats.hotplug_start_addr >> PAGE_SHIFT,
> + balloon_stats.hotplug_size >> PAGE_SHIFT);
> + balloon_stats.hotplug_start_addr = 0;
> + balloon_stats.hotplug_size = 0;
> + }
> +#else
> + if (current_target() != balloon_stats.current_pages)
> + mod_timer(&balloon_timer, jiffies + HZ);
> +#endif
>
> mutex_unlock(&balloon_mutex);
> }
> @@ -413,6 +489,11 @@
> balloon_stats.balloon_high = 0;
> balloon_stats.driver_pages = 0UL;
>
> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
> + balloon_stats.hotplug_start_addr = 0;
> + balloon_stats.hotplug_size = 0;
> +#endif
> +
> init_timer(&balloon_timer);
> balloon_timer.data = 0;
> balloon_timer.function = balloon_alarm;
> diff -Nru linux-2.6.32.16.orig/mm/Kconfig linux-2.6.32.16/mm/Kconfig
> --- linux-2.6.32.16.orig/mm/Kconfig 2010-07-05 20:14:00.000000000 +0200
> +++ linux-2.6.32.16/mm/Kconfig 2010-07-16 11:44:27.000000000 +0200
> @@ -140,6 +140,15 @@
> depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
> depends on MIGRATION
>
> +config XEN_MEMORY_HOTPLUG
> + bool "Allow for memory hot-add in Xen guests"
> + depends on EXPERIMENTAL && ARCH_MEMORY_PROBE && XEN
> + default n
> + help
> + Memory hot-add allows expanding memory available for the system
> + above limit declared at system startup. It is very useful on critical
> + systems which require long run without rebooting.
> +
> #
> # If we have space for more page flags then we can enable additional
> # optimizations and functionality.
You look to have the patch duplicated:
> diff -Nru linux-2.6.32.16.orig/drivers/base/memory.c linux-2.6.32.16/drivers/base/memory.c
> --- linux-2.6.32.16.orig/drivers/base/memory.c 2010-07-05 20:14:00.000000000 +0200
> +++ linux-2.6.32.16/drivers/base/memory.c 2010-07-16 11:48:45.000000000 +0200
> diff -Nru linux-2.6.32.16.orig/drivers/xen/Kconfig linux-2.6.32.16/drivers/xen/Kconfig
> --- linux-2.6.32.16.orig/drivers/xen/Kconfig 2010-07-05 20:14:00.000000000 +0200
> +++ linux-2.6.32.16/drivers/xen/Kconfig 2010-07-09 21:04:17.000000000 +0200
> diff -Nru linux-2.6.32.16.orig/drivers/xen/balloon.c linux-2.6.32.16/drivers/xen/balloon.c
> --- linux-2.6.32.16.orig/drivers/xen/balloon.c 2010-07-05 20:14:00.000000000 +0200
> +++ linux-2.6.32.16/drivers/xen/balloon.c 2010-07-16 15:06:53.000000000 +0200
--
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