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

From: Pavel Tatashin
Date: Mon Jul 08 2019 - 17:15:40 EST


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@xxxxxxxxxx>
---
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