kexec: Allocate decrypted control pages for kdump if SME is enabled

When SME is enabled in the first kernel, it needs to allocate decrypted
pages for kdump because when the kdump kernel boots, these pages need to
be accessed decrypted in the initial boot stage, before SME is enabled.

 [ bp: clean up text. ]
Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: kexec@lists.infradead.org
Cc: tglx@linutronix.de
Cc: mingo@redhat.com
Cc: hpa@zytor.com
Cc: akpm@linux-foundation.org
Cc: dan.j.williams@intel.com
Cc: bhelgaas@google.com
Cc: baiyaowei@cmss.chinamobile.com
Cc: tiwai@suse.de
Cc: brijesh.singh@amd.com
Cc: dyoung@redhat.com
Cc: bhe@redhat.com
Cc: jroedel@suse.de
Link: https://lkml.kernel.org/r/20180930031033.22110-3-lijiang@redhat.com

kernel/kexec_core.c

@@ -471,6 +471,10 @@ static struct page *kimage_alloc_crash_control_pages(struct kimage *image,
 		}
 	}
 
+	/* Ensure that these pages are decrypted if SME is enabled. */
+	if (pages)
+		arch_kexec_post_alloc_pages(page_address(pages), 1 << order, 0);
+
 	return pages;
 }
 
@@ -867,6 +871,7 @@ static int kimage_load_crash_segment(struct kimage *image,
 			result  = -ENOMEM;
 			goto out;
 		}
+		arch_kexec_post_alloc_pages(page_address(page), 1, 0);
 		ptr = kmap(page);
 		ptr += maddr & ~PAGE_MASK;
 		mchunk = min_t(size_t, mbytes,
@@ -884,6 +889,7 @@ static int kimage_load_crash_segment(struct kimage *image,
 			result = copy_from_user(ptr, buf, uchunk);
 		kexec_flush_icache_page(page);
 		kunmap(page);
+		arch_kexec_pre_free_pages(page_address(page), 1);
 		if (result) {
 			result = -EFAULT;
 			goto out;