| Message ID | 20190122080628.7238-3-jgross@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86: respect memory size limits | expand |
>>> On 22.01.19 at 09:06, <jgross@suse.com> wrote: > Don't allow memory to be added above the allowed maximum allocation > limit set by Xen. This reads as if the hypervisor was imposing a limit here, but looking at xen_get_max_pages(), xen_foreach_remap_area(), and xen_count_remap_pages() I take it that it's a restriction enforced by the Xen subsystem in Linux. Furthermore from the cover letter I imply that the observed issue was on a Dom0, yet xen_get_max_pages()'s use of XENMEM_maximum_reservation wouldn't impose any limit there at all (without use of the hypervisor option "dom0_mem=max:..."), would it? Jan
On 22/01/2019 09:52, Jan Beulich wrote: >>>> On 22.01.19 at 09:06, <jgross@suse.com> wrote: >> Don't allow memory to be added above the allowed maximum allocation >> limit set by Xen. > > This reads as if the hypervisor was imposing a limit here, but looking at > xen_get_max_pages(), xen_foreach_remap_area(), and > xen_count_remap_pages() I take it that it's a restriction enforced by > the Xen subsystem in Linux. Furthermore from the cover letter I imply > that the observed issue was on a Dom0, yet xen_get_max_pages()'s > use of XENMEM_maximum_reservation wouldn't impose any limit there > at all (without use of the hypervisor option "dom0_mem=max:..."), > would it? Oh yes, you are right, of course! I need to check the current reservation and adjust the allowed limit in case of ballooning and/or memory hotplug. Thanks for noticing that! Juergen
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c index d5f303c0e656..5929a6ba5c25 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> @@ -785,6 +786,10 @@ char * __init xen_memory_setup(void) /* How many extra pages do we need due to remapping? */ max_pages += xen_foreach_remap_area(max_pfn, xen_count_remap_pages); +#ifdef CONFIG_MEMORY_HOTPLUG + max_mem_size = PFN_PHYS(max_pages); +#endif + if (max_pages > max_pfn) extra_pages += max_pages - max_pfn;
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@suse.com> --- arch/x86/xen/setup.c | 5 +++++ 1 file changed, 5 insertions(+)