Commit 375b2a9a authored by Ian Campbell's avatar Ian Campbell Committed by Jeremy Fitzhardinge
Browse files

xen: correctly rebuild mfn list list after migration. 



Otherwise the second migration attempt fails because the mfn_list_list
still refers to all the old mfns.

We need to update the entires in both p2m_top_mfn and the mid_mfn
pages which p2m_top_mfn refers to.

In order to do this we need to keep track of the virtual addresses
mapping the p2m_mid_mfn pages since we cannot rely on
mfn_to_virt(p2m_top_mfn[idx]) since p2m_top_mfn[idx] will still
contain the old MFN after a migration, which may now belong to another
domain and hence have a different mapping in the m2p.

Therefore add and maintain a third top level page, p2m_top_mfn_p[],
which tracks the virtual addresses of the mfns contained in
p2m_top_mfn[].

We also need to update the content of the p2m_mid_missing_mfn page on
resume to refer to the page's new mfn.

p2m_missing does not need updating since the migration process takes
care of the leaf p2m pages for us.

Signed-off-by: default avatarIan Campbell <ian.campbell@citrix.com>
Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
parent cb52e6d9

arch/x86/xen/mmu.c

+37 −13
Original line number Diff line number Diff line
@@ -187,6 +187,8 @@ DEFINE_PER_CPU(unsigned long, xen_current_cr3); /* actual vcpu cr3 */ 
 *    / \      / \         /           /

 *  p2m p2m p2m p2m p2m p2m p2m ...

 *

 * The p2m_mid_mfn pages are mapped by p2m_top_mfn_p.

 *

 * The p2m_top and p2m_top_mfn levels are 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
@@ -211,6 +213,7 @@ static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE); 


static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);

static RESERVE_BRK_ARRAY(unsigned long *, p2m_top_mfn_p, P2M_TOP_PER_PAGE);



RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));

RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
@@ -247,6 +250,14 @@ static void p2m_top_mfn_init(unsigned long *top) 
		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_init(unsigned long **mid)

{

	unsigned i;
@@ -283,33 +294,43 @@ static void p2m_init(unsigned long *p2m) 
 */

void xen_build_mfn_list_list(void)

{

	unsigned pfn;

	unsigned long pfn;



	/* Pre-initialize p2m_top_mfn to be completely missing */

	if (p2m_top_mfn == NULL) {

		p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);

		p2m_mid_mfn_init(p2m_mid_missing_mfn);



		p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);

		p2m_top_mfn_p_init(p2m_top_mfn_p);



		p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);

		p2m_top_mfn_init(p2m_top_mfn);

	} else {

		/* Reinitialise, mfn's all change after migration */

		p2m_mid_mfn_init(p2m_mid_missing_mfn);

	}



	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {

		unsigned topidx = p2m_top_index(pfn);

		unsigned mididx = p2m_mid_index(pfn);

		unsigned long **mid;

		unsigned long mid_mfn;

		unsigned long *mid_mfn_p;



		mid = p2m_top[topidx];

		mid_mfn_p = p2m_top_mfn_p[topidx];



		/* Don't bother allocating any mfn mid levels if

		   they're just missing */

		if (mid[mididx] == p2m_missing)

		 * they're just missing, just update the stored mfn,

		 * since all could have changed over a migrate.

		 */

		if (mid == p2m_mid_missing) {

			BUG_ON(mididx);

			BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);

			p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);

			pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;

			continue;



		mid_mfn = p2m_top_mfn[topidx];

		mid_mfn_p = mfn_to_virt(mid_mfn);

		}



		if (mid_mfn_p == p2m_mid_missing_mfn) {

			/*
@@ -321,11 +342,10 @@ void xen_build_mfn_list_list(void) 
			mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);

			p2m_mid_mfn_init(mid_mfn_p);



			mid_mfn = virt_to_mfn(mid_mfn_p);

			

			p2m_top_mfn[topidx] = mid_mfn;

			p2m_top_mfn_p[topidx] = mid_mfn_p;

		}



		p2m_top_mfn[topidx] = virt_to_mfn(mid_mfn_p);

		mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);

	}

}
@@ -344,7 +364,7 @@ void __init xen_build_dynamic_phys_to_machine(void) 
{

	unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;

	unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);

	unsigned pfn;

	unsigned long pfn;



	xen_max_p2m_pfn = max_pfn;
@@ -434,7 +454,9 @@ static bool alloc_p2m(unsigned long pfn) 
	}



	top_mfn_p = &p2m_top_mfn[topidx];

	mid_mfn = mfn_to_virt(*top_mfn_p);

	mid_mfn = p2m_top_mfn_p[topidx];



	BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);



	if (mid_mfn == p2m_mid_missing_mfn) {

		/* Separately check the mid mfn level */
@@ -451,6 +473,8 @@ static bool alloc_p2m(unsigned long pfn) 
		mid_mfn_mfn = virt_to_mfn(mid_mfn);

		if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)

			free_p2m_page(mid_mfn);

		else

			p2m_top_mfn_p[topidx] = mid_mfn;

	}



	if (p2m_top[topidx][mididx] == p2m_missing) {

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