197ecb3802
Scrubbing pages on initial balloon down can take some time, especially in nested virtualization case (nested EPT is slow). When HVM/PVH guest is started with memory= significantly lower than maxmem=, all the extra pages will be scrubbed before returning to Xen. But since most of them weren't used at all at that point, Xen needs to populate them first (from populate-on-demand pool). In nested virt case (Xen inside KVM) this slows down the guest boot by 15-30s with just 1.5GB needed to be returned to Xen. Add runtime parameter to enable/disable it, to allow initially disabling scrubbing, then enable it back during boot (for example in initramfs). Such usage relies on assumption that a) most pages ballooned out during initial boot weren't used at all, and b) even if they were, very few secrets are in the guest at that time (before any serious userspace kicks in). Convert CONFIG_XEN_SCRUB_PAGES to CONFIG_XEN_SCRUB_PAGES_DEFAULT (also enabled by default), controlling default value for the new runtime switch. Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com> Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
123 lines
3.2 KiB
C
123 lines
3.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/******************************************************************************
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* Xen memory reservation utilities.
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*
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* Copyright (c) 2003, B Dragovic
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* Copyright (c) 2003-2004, M Williamson, K Fraser
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* Copyright (c) 2005 Dan M. Smith, IBM Corporation
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* Copyright (c) 2010 Daniel Kiper
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* Copyright (c) 2018 Oleksandr Andrushchenko, EPAM Systems Inc.
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*/
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#include <asm/xen/hypercall.h>
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#include <xen/interface/memory.h>
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#include <xen/mem-reservation.h>
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#include <linux/moduleparam.h>
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bool __read_mostly xen_scrub_pages = IS_ENABLED(CONFIG_XEN_SCRUB_PAGES_DEFAULT);
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core_param(xen_scrub_pages, xen_scrub_pages, bool, 0);
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/*
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* Use one extent per PAGE_SIZE to avoid to break down the page into
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* multiple frame.
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*/
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#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
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#ifdef CONFIG_XEN_HAVE_PVMMU
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void __xenmem_reservation_va_mapping_update(unsigned long count,
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struct page **pages,
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xen_pfn_t *frames)
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{
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int i;
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for (i = 0; i < count; i++) {
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struct page *page = pages[i];
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unsigned long pfn = page_to_pfn(page);
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BUG_ON(!page);
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/*
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* We don't support PV MMU when Linux and Xen is using
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* different page granularity.
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*/
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BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
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set_phys_to_machine(pfn, frames[i]);
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/* Link back into the page tables if not highmem. */
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if (!PageHighMem(page)) {
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int ret;
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ret = HYPERVISOR_update_va_mapping(
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(unsigned long)__va(pfn << PAGE_SHIFT),
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mfn_pte(frames[i], PAGE_KERNEL),
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0);
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BUG_ON(ret);
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}
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}
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}
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EXPORT_SYMBOL_GPL(__xenmem_reservation_va_mapping_update);
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void __xenmem_reservation_va_mapping_reset(unsigned long count,
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struct page **pages)
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{
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int i;
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for (i = 0; i < count; i++) {
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struct page *page = pages[i];
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unsigned long pfn = page_to_pfn(page);
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/*
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* We don't support PV MMU when Linux and Xen are using
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* different page granularity.
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*/
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BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
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if (!PageHighMem(page)) {
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int ret;
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ret = HYPERVISOR_update_va_mapping(
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(unsigned long)__va(pfn << PAGE_SHIFT),
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__pte_ma(0), 0);
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BUG_ON(ret);
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}
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__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
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}
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}
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EXPORT_SYMBOL_GPL(__xenmem_reservation_va_mapping_reset);
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#endif /* CONFIG_XEN_HAVE_PVMMU */
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/* @frames is an array of PFNs */
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int xenmem_reservation_increase(int count, xen_pfn_t *frames)
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{
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struct xen_memory_reservation reservation = {
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.address_bits = 0,
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.extent_order = EXTENT_ORDER,
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.domid = DOMID_SELF
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};
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/* XENMEM_populate_physmap requires a PFN based on Xen granularity. */
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set_xen_guest_handle(reservation.extent_start, frames);
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reservation.nr_extents = count;
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return HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
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}
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EXPORT_SYMBOL_GPL(xenmem_reservation_increase);
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/* @frames is an array of GFNs */
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int xenmem_reservation_decrease(int count, xen_pfn_t *frames)
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{
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struct xen_memory_reservation reservation = {
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.address_bits = 0,
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.extent_order = EXTENT_ORDER,
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.domid = DOMID_SELF
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};
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/* XENMEM_decrease_reservation requires a GFN */
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set_xen_guest_handle(reservation.extent_start, frames);
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reservation.nr_extents = count;
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return HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
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}
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EXPORT_SYMBOL_GPL(xenmem_reservation_decrease);
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