[PATCH 1/3] xen/mmu/p2m: Check extend_brk for NULL

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

Which allows us to be a bit smarter in case we exhaust the reserved
virtual space.

[v1: Suggested by Ian Campbell]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/xen/enlighten.c |    2 ++
 arch/x86/xen/mmu.c       |    5 ++++-
 arch/x86/xen/p2m.c       |   35 ++++++++++++++++++++++++-----------
 3 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 993e2a5..923d98e 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1519,6 +1519,8 @@ void __ref xen_hvm_init_shared_info(void)
 	if (!shared_info_page)
 		shared_info_page = (struct shared_info *)
 			extend_brk(PAGE_SIZE, PAGE_SIZE);
+	if (!shared_info_page)
+		return;
 	xatp.domid = DOMID_SELF;
 	xatp.idx = 0;
 	xatp.space = XENMAPSPACE_shared_info;
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 993ba07..d7a2044 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1711,6 +1711,8 @@ static void __init xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
 
 	level1_ident_pgt = extend_brk(sizeof(pte_t) * LEVEL1_IDENT_ENTRIES,
 				      PAGE_SIZE);
+	if (!level_ident_pgt)
+		goto out;
 
 	ident_pte = 0;
 	pfn = 0;
@@ -1750,7 +1752,7 @@ static void __init xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
 
 	for (pteidx = 0; pteidx < ident_pte; pteidx += PTRS_PER_PTE)
 		set_page_prot(&level1_ident_pgt[pteidx], PAGE_KERNEL_RO);
-
+out:
 	set_page_prot(pmd, PAGE_KERNEL_RO);
 }
 #endif
@@ -1948,6 +1950,7 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
 
 	initial_kernel_pmd =
 		extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
+	BUG_ON(!initial_kernel_pmd);
 
 	max_pfn_mapped = PFN_DOWN(__pa(xen_start_info->pt_base) +
 				  xen_start_info->nr_pt_frames * PAGE_SIZE +
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index bbfd085..1658af0 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -258,6 +258,13 @@ static void p2m_init(unsigned long *p2m)
 		p2m[i] = INVALID_P2M_ENTRY;
 }
 
+static __always_inline __init void *brk_alloc_page(void)
+{
+	void *p = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	/* So early that printk does not function. */
+	BUG_ON(p == NULL);
+	return p;
+}
 /*
  * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
  *
@@ -274,13 +281,13 @@ void __ref xen_build_mfn_list_list(void)
 
 	/* 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_missing_mfn = brk_alloc_page();
 		p2m_mid_mfn_init(p2m_mid_missing_mfn);
 
-		p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
+		p2m_top_mfn_p = brk_alloc_page();
 		p2m_top_mfn_p_init(p2m_top_mfn_p);
 
-		p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
+		p2m_top_mfn = brk_alloc_page();
 		p2m_top_mfn_init(p2m_top_mfn);
 	} else {
 		/* Reinitialise, mfn's all change after migration */
@@ -312,10 +319,10 @@ void __ref xen_build_mfn_list_list(void)
 			/*
 			 * XXX boot-time only!  We should never find
 			 * missing parts of the mfn tree after
-			 * runtime.  extend_brk() will BUG if we call
+			 * runtime.  brk_alloc_page() will BUG if we call
 			 * it too late.
 			 */
-			mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
+			mid_mfn_p = brk_alloc_page();
 			p2m_mid_mfn_init(mid_mfn_p);
 
 			p2m_top_mfn_p[topidx] = mid_mfn_p;
@@ -344,16 +351,16 @@ void __init xen_build_dynamic_phys_to_machine(void)
 
 	xen_max_p2m_pfn = max_pfn;
 
-	p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m_missing = brk_alloc_page();
 	p2m_init(p2m_missing);
 
-	p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m_mid_missing = brk_alloc_page();
 	p2m_mid_init(p2m_mid_missing);
 
-	p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m_top = brk_alloc_page();
 	p2m_top_init(p2m_top);
 
-	p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	p2m_identity = brk_alloc_page();
 	p2m_init(p2m_identity);
 
 	/*
@@ -366,7 +373,7 @@ void __init xen_build_dynamic_phys_to_machine(void)
 		unsigned mididx = p2m_mid_index(pfn);
 
 		if (p2m_top[topidx] == p2m_mid_missing) {
-			unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
+			unsigned long **mid = brk_alloc_page();
 			p2m_mid_init(mid);
 
 			p2m_top[topidx] = mid;
@@ -600,6 +607,8 @@ static bool __init early_alloc_p2m_middle(unsigned long pfn, bool check_boundary
 
 	/* Boundary cross-over for the edges: */
 	p2m = extend_brk(PAGE_SIZE, PAGE_SIZE);
+	if (!p2m)
+		return false;
 
 	p2m_init(p2m);
 
@@ -626,7 +635,8 @@ static bool __init early_alloc_p2m(unsigned long pfn)
 	mid_mfn_p = p2m_top_mfn_p[topidx];
 	if (mid == p2m_mid_missing) {
 		mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
-
+		if (!mid)
+			return false;
 		p2m_mid_init(mid);
 
 		p2m_top[topidx] = mid;
@@ -636,6 +646,8 @@ static bool __init early_alloc_p2m(unsigned long pfn)
 	/* And the save/restore P2M tables.. */
 	if (mid_mfn_p == p2m_mid_missing_mfn) {
 		mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
+		if (!mid_mfn_p)
+			return false;
 		p2m_mid_mfn_init(mid_mfn_p);
 
 		p2m_top_mfn_p[topidx] = mid_mfn_p;
@@ -762,6 +774,7 @@ static void __init m2p_override_init(void)
 
 	m2p_overrides = extend_brk(sizeof(*m2p_overrides) * M2P_OVERRIDE_HASH,
 				   sizeof(unsigned long));
+	BUG_ON(!m2p_overrides);
 
 	for (i = 0; i < M2P_OVERRIDE_HASH; i++)
 		INIT_LIST_HEAD(&m2p_overrides[i]);
-- 
1.7.7.6