add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/arch/x86/kernel/aperture_64.c
..
..
@@ -270,18 +270,23 @@
270
270
 }
271
271
 early_param("gart_fix_e820", parse_gart_mem);
272
272
 
273
+/*
274
+ * With kexec/kdump, if the first kernel doesn't shut down the GART and the
275
+ * second kernel allocates a different GART region, there might be two
276
+ * overlapping GART regions present:
277
+ *
278
+ * - the first still used by the GART initialized in the first kernel.
279
+ * - (sub-)set of it used as normal RAM by the second kernel.
280
+ *
281
+ * which leads to memory corruptions and a kernel panic eventually.
282
+ *
283
+ * This can also happen if the BIOS has forgotten to mark the GART region
284
+ * as reserved.
285
+ *
286
+ * Try to update the e820 map to mark that new region as reserved.
287
+ */
273
288
 void __init early_gart_iommu_check(void)
274
289
 {
275
-	/*
276
-	 * in case it is enabled before, esp for kexec/kdump,
277
-	 * previous kernel already enable that. memset called
278
-	 * by allocate_aperture/__alloc_bootmem_nopanic cause restart.
279
-	 * or second kernel have different position for GART hole. and new
280
-	 * kernel could use hole as RAM that is still used by GART set by
281
-	 * first kernel
282
-	 * or BIOS forget to put that in reserved.
283
-	 * try to update e820 to make that region as reserved.
284
-	 */
285
290
 	u32 agp_aper_order = 0;
286
291
 	int i, fix, slot, valid_agp = 0;
287
292
 	u32 ctl;