Messages in this thread | | | Date | Thu, 19 Mar 2015 18:05:48 +0100 | From | Juergen Gross <> | Subject | Re: [PATCH 1/2] xen: prepare p2m list for memory hotplug |
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On 03/19/2015 05:14 PM, Daniel Kiper wrote: > On Thu, Mar 19, 2015 at 03:31:01PM +0100, Juergen Gross wrote: >> Commit 054954eb051f35e74b75a566a96fe756015352c8 ("xen: switch to linear >> virtual mapped sparse p2m list") introduced a regression regarding to >> memory hotplug for a pv-domain: as the virtual space for the p2m list >> is allocated for the to be expected memory size of the domain only, >> hotplugged memory above that size will not be usable by the domain. >> >> Correct this by using a configurable size for the p2m list in case of >> memory hotplug enabled (default supported memory size is 512 GB for >> 64 bit domains and 4 GB for 32 bit domains). >> >> Signed-off-by: Juergen Gross <jgross@suse.com> >> --- >> arch/x86/xen/p2m.c | 13 ++++++++++++- >> drivers/xen/Kconfig | 13 +++++++++++++ >> 2 files changed, 25 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c >> index 9f93af5..30e84ae 100644 >> --- a/arch/x86/xen/p2m.c >> +++ b/arch/x86/xen/p2m.c >> @@ -91,6 +91,17 @@ EXPORT_SYMBOL_GPL(xen_p2m_size); >> unsigned long xen_max_p2m_pfn __read_mostly; >> EXPORT_SYMBOL_GPL(xen_max_p2m_pfn); >> >> +#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT >> +#ifdef CONFIG_X86_32 >> +BUILD_BUG_ON_MSG(CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT > 64) >> +#endif >> +#define P2M_LIMIT max(xen_max_p2m_pfn, \ >> + ((unsigned long)((u64)CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT * \ >> + 1024 * 1024 * 1024 / PAGE_SIZE))) >> +#else >> +#define P2M_LIMIT xen_max_p2m_pfn >> +#endif >> + >> static DEFINE_SPINLOCK(p2m_update_lock); >> >> static unsigned long *p2m_mid_missing_mfn; >> @@ -387,7 +398,7 @@ void __init xen_vmalloc_p2m_tree(void) >> static struct vm_struct vm; >> >> vm.flags = VM_ALLOC; >> - vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn, >> + vm.size = ALIGN(sizeof(unsigned long) * P2M_LIMIT, >> PMD_SIZE * PMDS_PER_MID_PAGE); > > What happens when somebody will allocate more memory for guest than > XEN_BALLOON_MEMORY_HOTPLUG_LIMIT? Additionally, I think that we do
It will fail to add like it does without this patch.
> not need allocate extra virtual address space if memory hotplug is > disabled.
As XEN_BALLOON_MEMORY_HOTPLUG_LIMIT depends on XEN_BALLOON_MEMORY_HOTPLUG which in turn depends on MEMORY_HOTPLUG, this is already the case.
> >> vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE); >> pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size); >> diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig >> index b812462..0a61ddf 100644 >> --- a/drivers/xen/Kconfig >> +++ b/drivers/xen/Kconfig >> @@ -55,6 +55,19 @@ config XEN_BALLOON_MEMORY_HOTPLUG >> >> In that case step 3 should be omitted. >> >> +config XEN_BALLOON_MEMORY_HOTPLUG_LIMIT >> + int >> + default 512 if X86_64 >> + default 4 if X86_32 >> + depends on XEN_HAVE_PVMMU > > Do we need dependency on XEN_HAVE_PVMMU?
Yes. Needed only for pv domains.
> If yes than maybe "depends on XEN_HAVE_PVMMU && XEN_BALLOON_MEMORY_HOTPLUG".
Matter of taste, I guess.
> >> + depends on XEN_BALLOON_MEMORY_HOTPLUG > > Should not this option be available even when memory hotplug is disabled?
Why?
Juergen
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