linux-kernel - [v1 4/5] kexec: use reserved memory for normal kexec reboot

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Date:   Mon,  8 Jul 2019 17:15:27 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     pasha.tatashin@...een.com, jmorris@...ei.org, sashal@...nel.org,
        ebiederm@...ssion.com, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, corbet@....net,
        catalin.marinas@....com, will@...nel.org,
        linux-doc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [v1 4/5] kexec: use reserved memory for normal kexec reboot

If memory was reserved for the given segment use it directly instead of
allocating on per-page bases. This will avoid relocating this segment to
final destination when machine is rebooted.

This is done on a per segment bases because user might decide to always
load kernel segments at the given address (i.e. non-relocatable kernel),
but load initramfs at reserved address, and thus save reboot time on
copying initramfs if it is large, and reduces reboot performance.

Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
---
 kernel/kexec_core.c | 39 ++++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 932feadbeb3a..2a8d8746e0a1 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -154,6 +154,18 @@ static struct page *kimage_alloc_page(struct kimage *image,
 				       gfp_t gfp_mask,
 				       unsigned long dest);
 
+/* Check whether this segment is fully within the resource */
+static bool segment_is_reserved(struct kexec_segment *seg, struct resource *res)
+{
+	unsigned long mstart = seg->mem;
+	unsigned long mend = mstart + seg->memsz - 1;
+
+	if (mstart < phys_to_boot_phys(res->start) ||
+	    mend > phys_to_boot_phys(res->end))
+		return false;
+	return true;
+}
+
 int sanity_check_segment_list(struct kimage *image)
 {
 	int i;
@@ -246,13 +258,9 @@ int sanity_check_segment_list(struct kimage *image)
 
 	if (image->type == KEXEC_TYPE_CRASH) {
 		for (i = 0; i < nr_segments; i++) {
-			unsigned long mstart, mend;
-
-			mstart = image->segment[i].mem;
-			mend = mstart + image->segment[i].memsz - 1;
 			/* Ensure we are within the crash kernel limits */
-			if ((mstart < phys_to_boot_phys(crashk_res.start)) ||
-			    (mend > phys_to_boot_phys(crashk_res.end)))
+			if (!segment_is_reserved(&image->segment[i],
+						 &crashk_res))
 				return -EADDRNOTAVAIL;
 		}
 	}
@@ -848,12 +856,13 @@ static int kimage_load_normal_segment(struct kimage *image,
 	return result;
 }
 
-static int kimage_load_crash_segment(struct kimage *image,
-					struct kexec_segment *segment)
+static int kimage_load_crash_or_reserved_segment(struct kimage *image,
+						 struct kexec_segment *segment)
 {
-	/* For crash dumps kernels we simply copy the data from
-	 * user space to it's destination.
-	 * We do things a page at a time for the sake of kmap.
+	/*
+	 * For crash dumps and kexec-reserved kernels we simply copy the data
+	 * from user space to it's destination. We do things a page at a time
+	 * for the sake of kmap.
 	 */
 	unsigned long maddr;
 	size_t ubytes, mbytes;
@@ -923,10 +932,14 @@ int kimage_load_segment(struct kimage *image,
 
 	switch (image->type) {
 	case KEXEC_TYPE_DEFAULT:
-		result = kimage_load_normal_segment(image, segment);
+		if (segment_is_reserved(segment, &kexeck_res))
+			result = kimage_load_crash_or_reserved_segment(image,
+								       segment);
+		else
+			result = kimage_load_normal_segment(image, segment);
 		break;
 	case KEXEC_TYPE_CRASH:
-		result = kimage_load_crash_segment(image, segment);
+		result = kimage_load_crash_or_reserved_segment(image, segment);
 		break;
 	}
 
-- 
2.22.0