1 files changed, 94 insertions, 12 deletions

diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
index 853f7dc3c21d..c2c067eff634 100644
--- a/drivers/firmware/efi/unaccepted_memory.c
+++ b/drivers/firmware/efi/unaccepted_memory.c
@@ -3,11 +3,21 @@
 #include <linux/efi.h>
 #include <linux/memblock.h>
 #include <linux/spinlock.h>
+#include <linux/crash_dump.h>
+#include <linux/nmi.h>
 #include <asm/unaccepted_memory.h>
 
-/* Protects unaccepted memory bitmap */
+/* Protects unaccepted memory bitmap and accepting_list */
 static DEFINE_SPINLOCK(unaccepted_memory_lock);
 
+struct accept_range {
+	struct list_head list;
+	unsigned long start;
+	unsigned long end;
+};
+
+static LIST_HEAD(accepting_list);
+
 /*
  * accept_memory() -- Consult bitmap and accept the memory if needed.
  *
@@ -20,10 +30,12 @@ static DEFINE_SPINLOCK(unaccepted_memory_lock);
  *  - memory that is below phys_base;
  *  - memory that is above the memory that addressable by the bitmap;
  */
-void accept_memory(phys_addr_t start, phys_addr_t end)
+void accept_memory(phys_addr_t start, unsigned long size)
 {
 	struct efi_unaccepted_memory *unaccepted;
 	unsigned long range_start, range_end;
+	struct accept_range range, *entry;
+	phys_addr_t end = start + size;
 	unsigned long flags;
 	u64 unit_size;
 
@@ -63,13 +75,13 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
 	 * "guard" page is accepted in addition to the memory that needs to be
 	 * used:
 	 *
-	 * 1. Implicitly extend the range_contains_unaccepted_memory(start, end)
-	 *    checks up to end+unit_size if 'end' is aligned on a unit_size
-	 *    boundary.
+	 * 1. Implicitly extend the range_contains_unaccepted_memory(start, size)
+	 *    checks up to the next unit_size if 'start+size' is aligned on a
+	 *    unit_size boundary.
 	 *
-	 * 2. Implicitly extend accept_memory(start, end) to end+unit_size if
-	 *    'end' is aligned on a unit_size boundary. (immediately following
-	 *    this comment)
+	 * 2. Implicitly extend accept_memory(start, size) to the next unit_size
+	 *    if 'size+end' is aligned on a unit_size boundary. (immediately
+	 *    following this comment)
 	 */
 	if (!(end % unit_size))
 		end += unit_size;
@@ -78,26 +90,77 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
 	if (end > unaccepted->size * unit_size * BITS_PER_BYTE)
 		end = unaccepted->size * unit_size * BITS_PER_BYTE;
 
-	range_start = start / unit_size;
-
+	range.start = start / unit_size;
+	range.end = DIV_ROUND_UP(end, unit_size);
+retry:
 	spin_lock_irqsave(&unaccepted_memory_lock, flags);
+
+	/*
+	 * Check if anybody works on accepting the same range of the memory.
+	 *
+	 * The check is done with unit_size granularity. It is crucial to catch
+	 * all accept requests to the same unit_size block, even if they don't
+	 * overlap on physical address level.
+	 */
+	list_for_each_entry(entry, &accepting_list, list) {
+		if (entry->end <= range.start)
+			continue;
+		if (entry->start >= range.end)
+			continue;
+
+		/*
+		 * Somebody else accepting the range. Or at least part of it.
+		 *
+		 * Drop the lock and retry until it is complete.
+		 */
+		spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
+		goto retry;
+	}
+
+	/*
+	 * Register that the range is about to be accepted.
+	 * Make sure nobody else will accept it.
+	 */
+	list_add(&range.list, &accepting_list);
+
+	range_start = range.start;
 	for_each_set_bitrange_from(range_start, range_end, unaccepted->bitmap,
-				   DIV_ROUND_UP(end, unit_size)) {
+				   range.end) {
 		unsigned long phys_start, phys_end;
 		unsigned long len = range_end - range_start;
 
 		phys_start = range_start * unit_size + unaccepted->phys_base;
 		phys_end = range_end * unit_size + unaccepted->phys_base;
 
+		/*
+		 * Keep interrupts disabled until the accept operation is
+		 * complete in order to prevent deadlocks.
+		 *
+		 * Enabling interrupts before calling arch_accept_memory()
+		 * creates an opportunity for an interrupt handler to request
+		 * acceptance for the same memory. The handler will continuously
+		 * spin with interrupts disabled, preventing other task from
+		 * making progress with the acceptance process.
+		 */
+		spin_unlock(&unaccepted_memory_lock);
+
 		arch_accept_memory(phys_start, phys_end);
+
+		spin_lock(&unaccepted_memory_lock);
 		bitmap_clear(unaccepted->bitmap, range_start, len);
 	}
+
+	list_del(&range.list);
+
+	touch_softlockup_watchdog();
+
 	spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
 }
 
-bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end)
+bool range_contains_unaccepted_memory(phys_addr_t start, unsigned long size)
 {
 	struct efi_unaccepted_memory *unaccepted;
+	phys_addr_t end = start + size;
 	unsigned long flags;
 	bool ret = false;
 	u64 unit_size;
@@ -145,3 +208,22 @@ bool range_contains_unaccepted_memory(phys_addr_t start, phys_addr_t end)
 
 	return ret;
 }
+
+#ifdef CONFIG_PROC_VMCORE
+static bool unaccepted_memory_vmcore_pfn_is_ram(struct vmcore_cb *cb,
+						unsigned long pfn)
+{
+	return !pfn_is_unaccepted_memory(pfn);
+}
+
+static struct vmcore_cb vmcore_cb = {
+	.pfn_is_ram = unaccepted_memory_vmcore_pfn_is_ram,
+};
+
+static int __init unaccepted_memory_init_kdump(void)
+{
+	register_vmcore_cb(&vmcore_cb);
+	return 0;
+}
+core_initcall(unaccepted_memory_init_kdump);
+#endif /* CONFIG_PROC_VMCORE */