[U-Boot] [PATCH 07/10] x86: fsp: Make sure HOB list is not overwritten by U-Boot

[Bin Meng]

Intel IvyBridge FSP seems to be buggy that it does not report memory
used by FSP itself as reserved in the resource descriptor HOB. The
FSP specification does not describe how resource descriptor HOBs are
generated by the FSP to describe what memory regions. It looks newer
FSPs like Queensbay and BayTrail do not have such issue. This causes
U-Boot relocation overwrites the important boot service data which is
used by FSP, and the subsequent call to fsp_notify() will fail.

To resolve this, we find out the lowest memory base address allocated
by FSP for the boot service data when walking through the HOB list in
fsp_get_usable_lowmem_top(). Check whether the memory top address is
below the FSP HOB list, and if not, use the lowest memory base address
allocated by FSP as the memory top address.

Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
---

 arch/x86/lib/fsp/fsp_support.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/arch/x86/lib/fsp/fsp_support.c b/arch/x86/lib/fsp/fsp_support.c
index 875c96a..d6bbe1a 100644
--- a/arch/x86/lib/fsp/fsp_support.c
+++ b/arch/x86/lib/fsp/fsp_support.c
@@ -223,7 +223,9 @@ u32 fsp_get_usable_lowmem_top(const void *hob_list)
 {
 	const struct hob_header *hdr;
 	struct hob_res_desc *res_desc;
+	struct hob_mem_alloc *res_mem;
 	phys_addr_t phys_start;
+	phys_addr_t mem_base = 0;
 	u32 top;
 
 	/* Get the HOB list for processing */
@@ -242,9 +244,34 @@ u32 fsp_get_usable_lowmem_top(const void *hob_list)
 					top += (u32)(res_desc->len);
 			}
 		}
+
+		/*
+		 * Find out the lowest memory base address allocated by FSP
+		 * for the boot service data
+		 */
+		if (hdr->type == HOB_TYPE_MEM_ALLOC) {
+			res_mem = (struct hob_mem_alloc *)hdr;
+			if (!mem_base)
+				mem_base = res_mem->mem_base;
+			if (res_mem->mem_base < mem_base)
+				mem_base = res_mem->mem_base;
+		}
+
 		hdr = get_next_hob(hdr);
 	}
 
+	/*
+	 * Check whether the memory top address is below the FSP HOB list.
+	 * If not, use the lowest memory base address allocated by FSP as
+	 * the memory top address. This is to prevent U-Boot relocation
+	 * overwrites the important boot service data which is used by FSP,
+	 * otherwise the subsequent call to fsp_notify() will fail.
+	 */
+	if (top > (u32)hob_list) {
+		debug("Adjust memory top address due to a buggy FSP\n");
+		top = (u32)mem_base;
+	}
+
 	return top;
 }
 
-- 
1.8.2.1