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|
/*
* Xen leaves the responsibility for maintaining p2m mappings to the
* guests themselves, but it must also access and update the p2m array
* during suspend/resume when all the pages are reallocated.
*
* The logical flat p2m table is mapped to a linear kernel memory area.
* For accesses by Xen a three-level tree linked via mfns only is set up to
* allow the address space to be sparse.
*
* Xen
* |
* p2m_top_mfn
* / \
* p2m_mid_mfn p2m_mid_mfn
* / /
* p2m p2m p2m ...
*
* The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.
*
* The p2m_top_mfn level is limited to 1 page, so the maximum representable
* pseudo-physical address space is:
* P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
*
* P2M_PER_PAGE depends on the architecture, as a mfn is always
* unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
* 512 and 1024 entries respectively.
*
* In short, these structures contain the Machine Frame Number (MFN) of the PFN.
*
* However not all entries are filled with MFNs. Specifically for all other
* leaf entries, or for the top root, or middle one, for which there is a void
* entry, we assume it is "missing". So (for example)
* pfn_to_mfn(0x90909090)=INVALID_P2M_ENTRY.
* We have a dedicated page p2m_missing with all entries being
* INVALID_P2M_ENTRY. This page may be referenced multiple times in the p2m
* list/tree in case there are multiple areas with P2M_PER_PAGE invalid pfns.
*
* We also have the possibility of setting 1-1 mappings on certain regions, so
* that:
* pfn_to_mfn(0xc0000)=0xc0000
*
* The benefit of this is, that we can assume for non-RAM regions (think
* PCI BARs, or ACPI spaces), we can create mappings easily because we
* get the PFN value to match the MFN.
*
* For this to work efficiently we have one new page p2m_identity. All entries
* in p2m_identity are set to INVALID_P2M_ENTRY type (Xen toolstack only
* recognizes that and MFNs, no other fancy value).
*
* On lookup we spot that the entry points to p2m_identity and return the
* identity value instead of dereferencing and returning INVALID_P2M_ENTRY.
* If the entry points to an allocated page, we just proceed as before and
* return the PFN. If the PFN has IDENTITY_FRAME_BIT set we unmask that in
* appropriate functions (pfn_to_mfn).
*
* The reason for having the IDENTITY_FRAME_BIT instead of just returning the
* PFN is that we could find ourselves where pfn_to_mfn(pfn)==pfn for a
* non-identity pfn. To protect ourselves against we elect to set (and get) the
* IDENTITY_FRAME_BIT on all identity mapped PFNs.
*/
#include <linux/init.h>
#include <linux/module.h>
#include <linux/list.h>
#include <linux/hash.h>
#include <linux/sched.h>
#include <linux/seq_file.h>
#include <linux/bootmem.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <asm/cache.h>
#include <asm/setup.h>
#include <asm/uaccess.h>
#include <asm/xen/page.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
#include <xen/balloon.h>
#include <xen/grant_table.h>
#include "multicalls.h"
#include "xen-ops.h"
#define P2M_MID_PER_PAGE (PAGE_SIZE / sizeof(unsigned long *))
#define P2M_TOP_PER_PAGE (PAGE_SIZE / sizeof(unsigned long **))
#define MAX_P2M_PFN (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
#define PMDS_PER_MID_PAGE (P2M_MID_PER_PAGE / PTRS_PER_PTE)
unsigned long *xen_p2m_addr __read_mostly;
EXPORT_SYMBOL_GPL(xen_p2m_addr);
unsigned long xen_p2m_size __read_mostly;
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
#define P2M_LIMIT CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
#else
#define P2M_LIMIT 0
#endif
static DEFINE_SPINLOCK(p2m_update_lock);
static unsigned long *p2m_mid_missing_mfn;
static unsigned long *p2m_top_mfn;
static unsigned long **p2m_top_mfn_p;
static unsigned long *p2m_missing;
static unsigned long *p2m_identity;
static pte_t *p2m_missing_pte;
static pte_t *p2m_identity_pte;
/*
* Hint at last populated PFN.
*
* Used to set HYPERVISOR_shared_info->arch.max_pfn so the toolstack
* can avoid scanning the whole P2M (which may be sized to account for
* hotplugged memory).
*/
static unsigned long xen_p2m_last_pfn;
static inline unsigned p2m_top_index(unsigned long pfn)
{
BUG_ON(pfn >= MAX_P2M_PFN);
return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
}
static inline unsigned p2m_mid_index(unsigned long pfn)
{
return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
}
static inline unsigned p2m_index(unsigned long pfn)
{
return pfn % P2M_PER_PAGE;
}
static void p2m_top_mfn_init(unsigned long *top)
{
unsigned i;
for (i = 0; i < P2M_TOP_PER_PAGE; i++)
top[i] = virt_to_mfn(p2m_mid_missing_mfn);
}
static void p2m_top_mfn_p_init(unsigned long **top)
{
unsigned i;
for (i = 0; i < P2M_TOP_PER_PAGE; i++)
top[i] = p2m_mid_missing_mfn;
}
static void p2m_mid_mfn_init(unsigned long *mid, unsigned long *leaf)
{
unsigned i;
for (i = 0; i < P2M_MID_PER_PAGE; i++)
mid[i] = virt_to_mfn(leaf);
}
static void p2m_init(unsigned long *p2m)
{
unsigned i;
for (i = 0; i < P2M_PER_PAGE; i++)
p2m[i] = INVALID_P2M_ENTRY;
}
static void p2m_init_identity(unsigned long *p2m, unsigned long pfn)
{
unsigned i;
for (i = 0; i < P2M_PER_PAGE; i++)
p2m[i] = IDENTITY_FRAME(pfn + i);
}
static void * __ref alloc_p2m_page(void)
{
if (unlikely(!slab_is_available()))
return alloc_bootmem_align(PAGE_SIZE, PAGE_SIZE);
return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
}
static void __ref free_p2m_page(void *p)
{
if (unlikely(!slab_is_available())) {
free_bootmem((unsigned long)p, PAGE_SIZE);
return;
}
free_page((unsigned long)p);
}
/*
* Build the parallel p2m_top_mfn and p2m_mid_mfn structures
*
* This is called both at boot time, and after resuming from suspend:
* - At boot time we're called rather early, and must use alloc_bootmem*()
* to allocate memory.
*
* - After resume we're called from within stop_machine, but the mfn
* tree should already be completely allocated.
*/
void __ref xen_build_mfn_list_list(void)
{
unsigned long pfn, mfn;
pte_t *ptep;
unsigned int level, topidx, mididx;
unsigned long *mid_mfn_p;
if (xen_feature(XENFEAT_auto_translated_physmap) ||
xen_start_info->flags & SIF_VIRT_P2M_4TOOLS)
return;
/* Pre-initialize p2m_top_mfn to be completely missing */
if (p2m_top_mfn == NULL) {
p2m_mid_missing_mfn = alloc_p2m_page();
p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
p2m_top_mfn_p = alloc_p2m_page();
p2m_top_mfn_p_init(p2m_top_mfn_p);
p2m_top_mfn = alloc_p2m_page();
p2m_top_mfn_init(p2m_top_mfn);
} else {
/* Reinitialise, mfn's all change after migration */
p2m_mid_mfn_init(p2m_mid_missing_mfn, p2m_missing);
}
for (pfn = 0; pfn < xen_max_p2m_pfn && pfn < MAX_P2M_PFN;
pfn += P2M_PER_PAGE) {
topidx = p2m_top_index(pfn);
mididx = p2m_mid_index(pfn
|