[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [PATCH v2][v2.6.29][XEN] Return unused memory to hypervisor
----- Original Message ----- From: "Gianluca Guida" <gianluca.guida@xxxxxxxxxx> To: "Miroslav Rezanina" <mrezanin@xxxxxxxxxx> Cc: jeremy@xxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx Sent: Thursday, August 20, 2009 11:31:34 AM GMT +01:00 Amsterdam / Berlin / Bern / Rome / Stockholm / Vienna Subject: [Xen-devel] [PATCH][v2.6.29][XEN] Return unused memory to hypervisor Miroslav Rezanina writes: > > Hi, > > > > when running linux as XEN guest and use boot parameter mem= to set memory > > lower then is assigned to guest, not used memory should be returned to > > hypervisor as free. This is working with kernel available on xen.org pages, > > but is not working with kernel 2.6.29. Comparing both kernels I found code > > for returning unused memory to hypervisor is missing. Following patch add > > this functionality to 2.6.29 kernel. > > > > A good idea would be to avoid putting this code in the generic kernel > code. For now just placing it in at the end of Xen's post-allocator > init would make it completely transparent to the non-xen kernel. > Hi Gianluca, good point. You're right. I moved calling to xen_post_allocator_init function. It is better place for it. Regards, Mirek ----diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index b58e963..2a9cc80 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -28,6 +28,7 @@ #include <linux/console.h> #include <xen/interface/xen.h> +#include <xen/interface/memory.h> #include <xen/interface/version.h> #include <xen/interface/physdev.h> #include <xen/interface/vcpu.h> @@ -122,6 +123,36 @@ static int have_vcpu_info_placement = #endif ; +/** + * * Author: Miroslav Rezanina <mrezanin@xxxxxxxxxx> + * * Function retuns unused memory to hypevisor + * **/ +void __init xen_return_unused_mem(void) +{ + if (xen_start_info->nr_pages > max_pfn) { + /* + * the max_pfn was shrunk (probably by mem= + * kernel parameter); shrink reservation with the HV + */ + struct xen_memory_reservation reservation = { + .address_bits = 0, + .extent_order = 0, + .domid = DOMID_SELF + }; + unsigned int difference; + int ret; + + difference = xen_start_info->nr_pages - max_pfn; + + set_xen_guest_handle(reservation.extent_start, + ((unsigned long *)xen_start_info->mfn_list) + max_pfn); + reservation.nr_extents = difference; + ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, + &reservation); + BUG_ON (ret != difference); + } +} + static void xen_vcpu_setup(int cpu) { @@ -1057,6 +1088,8 @@ static __init void xen_post_allocator_init(void) SetPagePinned(virt_to_page(level3_user_vsyscall)); #endif xen_mark_init_mm_pinned(); + + xen_return_unused_mem(); } /* This is called once we have the cpu_possible_map */ _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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