On 1/30/19 3:22 AM, Juergen Gross wrote:
> Don't allow memory to be added above the allowed maximum allocation
> limit set by Xen.
>
> Trying to do so would result in cases like the following:
>
> [ 584.559652] ------------[ cut here ]------------
> [ 584.564897] WARNING: CPU: 2 PID: 1 at ../arch/x86/xen/multicalls.c:129 xen_alloc_pte+0x1c7/0x390()
> [ 584.575151] Modules linked in:
> [ 584.578643] Supported: Yes
> [ 584.581750] CPU: 2 PID: 1 Comm: swapper/0 Not tainted 4.4.120-92.70-default #1
> [ 584.590000] Hardware name: Cisco Systems Inc UCSC-C460-M4/UCSC-C460-M4, BIOS C460M4.4.0.1b.0.0629181419 06/29/2018
> [ 584.601862] 0000000000000000 ffffffff813175a0 0000000000000000 ffffffff8184777c
> [ 584.610200] ffffffff8107f4e1 ffff880487eb7000 ffff8801862b79c0 ffff88048608d290
> [ 584.618537] 0000000000487eb7 ffffea0000000201 ffffffff81009de7 ffffffff81068561
> [ 584.626876] Call Trace:
> [ 584.629699] [<ffffffff81019ad9>] dump_trace+0x59/0x340
> [ 584.635645] [<ffffffff81019eaa>] show_stack_log_lvl+0xea/0x170
> [ 584.642391] [<ffffffff8101ac51>] show_stack+0x21/0x40
> [ 584.648238] [<ffffffff813175a0>] dump_stack+0x5c/0x7c
> [ 584.654085] [<ffffffff8107f4e1>] warn_slowpath_common+0x81/0xb0
> [ 584.660932] [<ffffffff81009de7>] xen_alloc_pte+0x1c7/0x390
> [ 584.667289] [<ffffffff810647f0>] pmd_populate_kernel.constprop.6+0x40/0x80
> [ 584.675241] [<ffffffff815ecfe8>] phys_pmd_init+0x210/0x255
> [ 584.681587] [<ffffffff815ed207>] phys_pud_init+0x1da/0x247
> [ 584.687931] [<ffffffff815edb3b>] kernel_physical_mapping_init+0xf5/0x1d4
> [ 584.695682] [<ffffffff815e9bdd>] init_memory_mapping+0x18d/0x380
> [ 584.702631] [<ffffffff81064699>] arch_add_memory+0x59/0xf0
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> ---
> arch/x86/xen/setup.c | 10 ++++++++++
> drivers/xen/xen-balloon.c | 6 ++++++
> 2 files changed, 16 insertions(+)
>
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index d5f303c0e656..fdb184cadaf5 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -12,6 +12,7 @@
> #include <linux/memblock.h>
> #include <linux/cpuidle.h>
> #include <linux/cpufreq.h>
> +#include <linux/memory_hotplug.h>
>
> #include <asm/elf.h>
> #include <asm/vdso.h>
> @@ -825,6 +826,15 @@ char * __init xen_memory_setup(void)
> xen_max_p2m_pfn = pfn_s + n_pfns;
> } else
> discard = true;
> +#ifdef CONFIG_MEMORY_HOTPLUG
> + /*
> + * Don't allow adding memory not in E820 map while
> + * booting the system. Once the balloon driver is up
> + * it will remove that restriction again.
> + */
> + max_mem_size = xen_e820_table.entries[i].addr +
> + xen_e820_table.entries[i].size;
> +#endif
> }
>
> if (!discard)
> diff --git a/drivers/xen/xen-balloon.c b/drivers/xen/xen-balloon.c
> index 2acbfe104e46..2a960fcc812e 100644
> --- a/drivers/xen/xen-balloon.c
> +++ b/drivers/xen/xen-balloon.c
> @@ -37,6 +37,7 @@
> #include <linux/mm_types.h>
> #include <linux/init.h>
> #include <linux/capability.h>
> +#include <linux/memory_hotplug.h>
>
> #include <xen/xen.h>
> #include <xen/interface/xen.h>
> @@ -63,6 +64,11 @@ static void watch_target(struct xenbus_watch *watch,
> static bool watch_fired;
> static long target_diff;
>
> +#ifdef CONFIG_MEMORY_HOTPLUG
> + /* The balloon driver will take care of adding memory now. */
> + max_mem_size = U64_MAX;
> +#endif
I don't think I understand this. Are you saying the guest should ignore
'mem' boot option?
-boris
> +
> err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
> if (err != 1) {
> /* This is ok (for domain0 at least) - so just return */
