Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Daniel Kiper]

> Hmm... this code is being redone at the moment... this might conflict.

Is this available somewhere? May I have a look at it?

Daniel

PS I am on holiday until 02/01/2013 and I could not
   have access to my email box. Please be patient.
   At worst case I will send reply when I will be
   back at office.

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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Borislav Petkov]

On Thu, Dec 27, 2012 at 03:19:24PM -0800, Daniel Kiper wrote:
> > Hmm... this code is being redone at the moment... this might conflict.
> 
> Is this available somewhere? May I have a look at it?

http://marc.info/?l=linux-kernel&m=135581534620383

The for-x86-boot-v7 and -v8 branches.

HTH.

-- 
Regards/Gruss,
Boris.

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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Daniel Kiper]

On Fri, Dec 28, 2012 at 01:59:27PM +0100, Borislav Petkov wrote:
> On Thu, Dec 27, 2012 at 03:19:24PM -0800, Daniel Kiper wrote:
> > > Hmm... this code is being redone at the moment... this might conflict.
> >
> > Is this available somewhere? May I have a look at it?
>
> http://marc.info/?l=linux-kernel&m=135581534620383
>
> The for-x86-boot-v7 and -v8 branches.
>
> HTH.

Thanks.

Daniel

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[PATCH v3 00/11] xen: Initial kexec/kdump implementation

[Daniel Kiper]

Hi,

This set of patches contains initial kexec/kdump implementation for Xen v3.
Currently only dom0 is supported, however, almost all infrustructure
required for domU support is ready.

Jan Beulich suggested to merge Xen x86 assembler code with baremetal x86 code.
This could simplify and reduce a bit size of kernel code. However, this solution
requires some changes in baremetal x86 code. First of all code which establishes
transition page table should be moved back from machine_kexec_$(BITS).c to
relocate_kernel_$(BITS).S. Another important thing which should be changed in that
case is format of page_list array. Xen kexec hypercall requires to alternate physical
addresses with virtual ones. These and other required stuff have not been done in that
version because I am not sure that solution will be accepted by kexec/kdump maintainers.
I hope that this email spark discussion about that topic.

Daniel

 arch/x86/Kconfig                     |    3 +
 arch/x86/include/asm/kexec.h         |   10 +-
 arch/x86/include/asm/xen/hypercall.h |    6 +
 arch/x86/include/asm/xen/kexec.h     |   79 ++++
 arch/x86/kernel/machine_kexec_64.c   |   12 +-
 arch/x86/kernel/vmlinux.lds.S        |    7 +-
 arch/x86/xen/Kconfig                 |    1 +
 arch/x86/xen/Makefile                |    3 +
 arch/x86/xen/enlighten.c             |   11 +
 arch/x86/xen/kexec.c                 |  150 +++++++
 arch/x86/xen/machine_kexec_32.c      |  226 +++++++++++
 arch/x86/xen/machine_kexec_64.c      |  318 +++++++++++++++
 arch/x86/xen/relocate_kernel_32.S    |  323 +++++++++++++++
 arch/x86/xen/relocate_kernel_64.S    |  309 ++++++++++++++
 drivers/xen/sys-hypervisor.c         |   42 ++-
 include/linux/kexec.h                |   26 ++-
 include/xen/interface/xen.h          |   33 ++
 kernel/Makefile                      |    1 +
 kernel/kexec-firmware.c              |  743 ++++++++++++++++++++++++++++++++++
 kernel/kexec.c                       |   46 ++-
 20 files changed, 2331 insertions(+), 18 deletions(-)

Daniel Kiper (11):
      kexec: introduce kexec firmware support
      x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE
      xen: Introduce architecture independent data for kexec/kdump
      x86/xen: Introduce architecture dependent data for kexec/kdump
      x86/xen: Register resources required by kexec-tools
      x86/xen: Add i386 kexec/kdump implementation
      x86/xen: Add x86_64 kexec/kdump implementation
      x86/xen: Add kexec/kdump Kconfig and makefile rules
      x86/xen/enlighten: Add init and crash kexec/kdump hooks
      drivers/xen: Export vmcoreinfo through sysfs
      x86: Add Xen kexec control code size check to linker script

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[PATCH v3 01/11] kexec: introduce kexec firmware support

[Daniel Kiper]

Some kexec/kdump implementations (e.g. Xen PVOPS) could not use default
Linux infrastructure and require some support from firmware and/or hypervisor.
To cope with that problem kexec firmware infrastructure was introduced.
It allows a developer to use all kexec/kdump features of given firmware
or hypervisor.

v3 - suggestions/fixes:
   - replace kexec_ops struct by kexec firmware infrastructure
     (suggested by Eric Biederman).

v2 - suggestions/fixes:
   - add comment for kexec_ops.crash_alloc_temp_store member
     (suggested by Konrad Rzeszutek Wilk),
   - simplify kexec_ops usage
     (suggested by Konrad Rzeszutek Wilk).

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 include/linux/kexec.h   |   26 ++-
 kernel/Makefile         |    1 +
 kernel/kexec-firmware.c |  743 +++++++++++++++++++++++++++++++++++++++++++++++
 kernel/kexec.c          |   46 +++-
 4 files changed, 809 insertions(+), 7 deletions(-)
 create mode 100644 kernel/kexec-firmware.c

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index d0b8458..9568457 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -116,17 +116,34 @@ struct kimage {
 #endif
 };
 
-
-
 /* kexec interface functions */
 extern void machine_kexec(struct kimage *image);
 extern int machine_kexec_prepare(struct kimage *image);
 extern void machine_kexec_cleanup(struct kimage *image);
+extern struct page *mf_kexec_kimage_alloc_pages(gfp_t gfp_mask,
+						unsigned int order,
+						unsigned long limit);
+extern void mf_kexec_kimage_free_pages(struct page *page);
+extern unsigned long mf_kexec_page_to_pfn(struct page *page);
+extern struct page *mf_kexec_pfn_to_page(unsigned long mfn);
+extern unsigned long mf_kexec_virt_to_phys(volatile void *address);
+extern void *mf_kexec_phys_to_virt(unsigned long address);
+extern int mf_kexec_prepare(struct kimage *image);
+extern int mf_kexec_load(struct kimage *image);
+extern void mf_kexec_cleanup(struct kimage *image);
+extern void mf_kexec_unload(struct kimage *image);
+extern void mf_kexec_shutdown(void);
+extern void mf_kexec(struct kimage *image);
 extern asmlinkage long sys_kexec_load(unsigned long entry,
 					unsigned long nr_segments,
 					struct kexec_segment __user *segments,
 					unsigned long flags);
+extern long firmware_sys_kexec_load(unsigned long entry,
+					unsigned long nr_segments,
+					struct kexec_segment __user *segments,
+					unsigned long flags);
 extern int kernel_kexec(void);
+extern int firmware_kernel_kexec(void);
 #ifdef CONFIG_COMPAT
 extern asmlinkage long compat_sys_kexec_load(unsigned long entry,
 				unsigned long nr_segments,
@@ -135,7 +152,10 @@ extern asmlinkage long compat_sys_kexec_load(unsigned long entry,
 #endif
 extern struct page *kimage_alloc_control_pages(struct kimage *image,
 						unsigned int order);
+extern struct page *firmware_kimage_alloc_control_pages(struct kimage *image,
+							unsigned int order);
 extern void crash_kexec(struct pt_regs *);
+extern void firmware_crash_kexec(struct pt_regs *);
 int kexec_should_crash(struct task_struct *);
 void crash_save_cpu(struct pt_regs *regs, int cpu);
 void crash_save_vmcoreinfo(void);
@@ -168,6 +188,8 @@ unsigned long paddr_vmcoreinfo_note(void);
 #define VMCOREINFO_CONFIG(name) \
 	vmcoreinfo_append_str("CONFIG_%s=y\n", #name)
 
+extern bool kexec_use_firmware;
+
 extern struct kimage *kexec_image;
 extern struct kimage *kexec_crash_image;
 
diff --git a/kernel/Makefile b/kernel/Makefile
index 6c072b6..bc96b2f 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -58,6 +58,7 @@ obj-$(CONFIG_MODULE_SIG) += module_signing.o modsign_pubkey.o modsign_certificat
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o
+obj-$(CONFIG_KEXEC_FIRMWARE) += kexec-firmware.o
 obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
 obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CGROUPS) += cgroup.o
diff --git a/kernel/kexec-firmware.c b/kernel/kexec-firmware.c
new file mode 100644
index 0000000..f6ddd4c
--- /dev/null
+++ b/kernel/kexec-firmware.c
@@ -0,0 +1,743 @@
+/*
+ * Copyright (C) 2002-2004 Eric Biederman  <ebiederm@xmission.com>
+ * Copyright (C) 2012 Daniel Kiper, Oracle Corporation
+ *
+ * Most of the code here is a copy of kernel/kexec.c.
+ *
+ * This source code is licensed under the GNU General Public License,
+ * Version 2.  See the file COPYING for more details.
+ */
+
+#include <linux/atomic.h>
+#include <linux/errno.h>
+#include <linux/highmem.h>
+#include <linux/kernel.h>
+#include <linux/kexec.h>
+#include <linux/list.h>
+#include <linux/mm.h>
+#include <linux/reboot.h>
+#include <linux/slab.h>
+
+#include <asm/uaccess.h>
+
+/*
+ * KIMAGE_NO_DEST is an impossible destination address..., for
+ * allocating pages whose destination address we do not care about.
+ */
+#define KIMAGE_NO_DEST (-1UL)
+
+static int kimage_is_destination_range(struct kimage *image,
+				       unsigned long start, unsigned long end);
+static struct page *kimage_alloc_page(struct kimage *image,
+				       gfp_t gfp_mask,
+				       unsigned long dest);
+
+static int do_kimage_alloc(struct kimage **rimage, unsigned long entry,
+	                    unsigned long nr_segments,
+                            struct kexec_segment __user *segments)
+{
+	size_t segment_bytes;
+	struct kimage *image;
+	unsigned long i;
+	int result;
+
+	/* Allocate a controlling structure */
+	result = -ENOMEM;
+	image = kzalloc(sizeof(*image), GFP_KERNEL);
+	if (!image)
+		goto out;
+
+	image->head = 0;
+	image->entry = &image->head;
+	image->last_entry = &image->head;
+	image->control_page = ~0; /* By default this does not apply */
+	image->start = entry;
+	image->type = KEXEC_TYPE_DEFAULT;
+
+	/* Initialize the list of control pages */
+	INIT_LIST_HEAD(&image->control_pages);
+
+	/* Initialize the list of destination pages */
+	INIT_LIST_HEAD(&image->dest_pages);
+
+	/* Initialize the list of unusable pages */
+	INIT_LIST_HEAD(&image->unuseable_pages);
+
+	/* Read in the segments */
+	image->nr_segments = nr_segments;
+	segment_bytes = nr_segments * sizeof(*segments);
+	result = copy_from_user(image->segment, segments, segment_bytes);
+	if (result) {
+		result = -EFAULT;
+		goto out;
+	}
+
+	/*
+	 * Verify we have good destination addresses.  The caller is
+	 * responsible for making certain we don't attempt to load
+	 * the new image into invalid or reserved areas of RAM.  This
+	 * just verifies it is an address we can use.
+	 *
+	 * Since the kernel does everything in page size chunks ensure
+	 * the destination addresses are page aligned.  Too many
+	 * special cases crop of when we don't do this.  The most
+	 * insidious is getting overlapping destination addresses
+	 * simply because addresses are changed to page size
+	 * granularity.
+	 */
+	result = -EADDRNOTAVAIL;
+	for (i = 0; i < nr_segments; i++) {
+		unsigned long mstart, mend;
+
+		mstart = image->segment[i].mem;
+		mend   = mstart + image->segment[i].memsz;
+		if ((mstart & ~PAGE_MASK) || (mend & ~PAGE_MASK))
+			goto out;
+		if (mend >= KEXEC_DESTINATION_MEMORY_LIMIT)
+			goto out;
+	}
+
+	/* Verify our destination addresses do not overlap.
+	 * If we alloed overlapping destination addresses
+	 * through very weird things can happen with no
+	 * easy explanation as one segment stops on another.
+	 */
+	result = -EINVAL;
+	for (i = 0; i < nr_segments; i++) {
+		unsigned long mstart, mend;
+		unsigned long j;
+
+		mstart = image->segment[i].mem;
+		mend   = mstart + image->segment[i].memsz;
+		for (j = 0; j < i; j++) {
+			unsigned long pstart, pend;
+			pstart = image->segment[j].mem;
+			pend   = pstart + image->segment[j].memsz;
+			/* Do the segments overlap ? */
+			if ((mend > pstart) && (mstart < pend))
+				goto out;
+		}
+	}
+
+	/* Ensure our buffer sizes are strictly less than
+	 * our memory sizes.  This should always be the case,
+	 * and it is easier to check up front than to be surprised
+	 * later on.
+	 */
+	result = -EINVAL;
+	for (i = 0; i < nr_segments; i++) {
+		if (image->segment[i].bufsz > image->segment[i].memsz)
+			goto out;
+	}
+
+	result = 0;
+out:
+	if (result == 0)
+		*rimage = image;
+	else
+		kfree(image);
+
+	return result;
+
+}
+
+static int kimage_normal_alloc(struct kimage **rimage, unsigned long entry,
+				unsigned long nr_segments,
+				struct kexec_segment __user *segments)
+{
+	int result;
+	struct kimage *image;
+
+	/* Allocate and initialize a controlling structure */
+	image = NULL;
+	result = do_kimage_alloc(&image, entry, nr_segments, segments);
+	if (result)
+		goto out;
+
+	*rimage = image;
+
+	/*
+	 * Find a location for the control code buffer, and add it
+	 * the vector of segments so that it's pages will also be
+	 * counted as destination pages.
+	 */
+	result = -ENOMEM;
+	image->control_code_page = firmware_kimage_alloc_control_pages(image,
+					   get_order(KEXEC_CONTROL_PAGE_SIZE));
+	if (!image->control_code_page) {
+		printk(KERN_ERR "Could not allocate control_code_buffer\n");
+		goto out;
+	}
+
+	image->swap_page = firmware_kimage_alloc_control_pages(image, 0);
+	if (!image->swap_page) {
+		printk(KERN_ERR "Could not allocate swap buffer\n");
+		goto out;
+	}
+
+	result = 0;
+ out:
+	if (result == 0)
+		*rimage = image;
+	else
+		kfree(image);
+
+	return result;
+}
+
+static int kimage_crash_alloc(struct kimage **rimage, unsigned long entry,
+				unsigned long nr_segments,
+				struct kexec_segment __user *segments)
+{
+	int result;
+	struct kimage *image;
+	unsigned long i;
+
+	image = NULL;
+	/* Verify we have a valid entry point */
+	if ((entry < crashk_res.start) || (entry > crashk_res.end)) {
+		result = -EADDRNOTAVAIL;
+		goto out;
+	}
+
+	/* Allocate and initialize a controlling structure */
+	result = do_kimage_alloc(&image, entry, nr_segments, segments);
+	if (result)
+		goto out;
+
+	/* Enable the special crash kernel control page
+	 * allocation policy.
+	 */
+	image->control_page = crashk_res.start;
+	image->type = KEXEC_TYPE_CRASH;
+
+	/*
+	 * Verify we have good destination addresses.  Normally
+	 * the caller is responsible for making certain we don't
+	 * attempt to load the new image into invalid or reserved
+	 * areas of RAM.  But crash kernels are preloaded into a
+	 * reserved area of ram.  We must ensure the addresses
+	 * are in the reserved area otherwise preloading the
+	 * kernel could corrupt things.
+	 */
+	result = -EADDRNOTAVAIL;
+	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 < crashk_res.start) || (mend > crashk_res.end))
+			goto out;
+	}
+
+	/*
+	 * Find a location for the control code buffer, and add
+	 * the vector of segments so that it's pages will also be
+	 * counted as destination pages.
+	 */
+	result = -ENOMEM;
+	image->control_code_page = firmware_kimage_alloc_control_pages(image,
+					   get_order(KEXEC_CONTROL_PAGE_SIZE));
+	if (!image->control_code_page) {
+		printk(KERN_ERR "Could not allocate control_code_buffer\n");
+		goto out;
+	}
+
+	result = 0;
+out:
+	if (result == 0)
+		*rimage = image;
+	else
+		kfree(image);
+
+	return result;
+}
+
+static int kimage_is_destination_range(struct kimage *image,
+					unsigned long start,
+					unsigned long end)
+{
+	unsigned long i;
+
+	for (i = 0; i < image->nr_segments; i++) {
+		unsigned long mstart, mend;
+
+		mstart = image->segment[i].mem;
+		mend = mstart + image->segment[i].memsz;
+		if ((end > mstart) && (start < mend))
+			return 1;
+	}
+
+	return 0;
+}
+
+static void kimage_free_page_list(struct list_head *list)
+{
+	struct list_head *pos, *next;
+
+	list_for_each_safe(pos, next, list) {
+		struct page *page;
+
+		page = list_entry(pos, struct page, lru);
+		list_del(&page->lru);
+		mf_kexec_kimage_free_pages(page);
+	}
+}
+
+static struct page *kimage_alloc_normal_control_pages(struct kimage *image,
+							unsigned int order)
+{
+	/* Control pages are special, they are the intermediaries
+	 * that are needed while we copy the rest of the pages
+	 * to their final resting place.  As such they must
+	 * not conflict with either the destination addresses
+	 * or memory the kernel is already using.
+	 *
+	 * The only case where we really need more than one of
+	 * these are for architectures where we cannot disable
+	 * the MMU and must instead generate an identity mapped
+	 * page table for all of the memory.
+	 *
+	 * At worst this runs in O(N) of the image size.
+	 */
+	struct list_head extra_pages;
+	struct page *pages;
+	unsigned int count;
+
+	count = 1 << order;
+	INIT_LIST_HEAD(&extra_pages);
+
+	/* Loop while I can allocate a page and the page allocated
+	 * is a destination page.
+	 */
+	do {
+		unsigned long pfn, epfn, addr, eaddr;
+
+		pages = mf_kexec_kimage_alloc_pages(GFP_KERNEL, order,
+							KEXEC_CONTROL_MEMORY_LIMIT);
+		if (!pages)
+			break;
+		pfn   = mf_kexec_page_to_pfn(pages);
+		epfn  = pfn + count;
+		addr  = pfn << PAGE_SHIFT;
+		eaddr = epfn << PAGE_SHIFT;
+		if ((epfn >= (KEXEC_CONTROL_MEMORY_LIMIT >> PAGE_SHIFT)) ||
+			      kimage_is_destination_range(image, addr, eaddr)) {
+			list_add(&pages->lru, &extra_pages);
+			pages = NULL;
+		}
+	} while (!pages);
+
+	if (pages) {
+		/* Remember the allocated page... */
+		list_add(&pages->lru, &image->control_pages);
+
+		/* Because the page is already in it's destination
+		 * location we will never allocate another page at
+		 * that address.  Therefore mf_kexec_kimage_alloc_pages
+		 * will not return it (again) and we don't need
+		 * to give it an entry in image->segment[].
+		 */
+	}
+	/* Deal with the destination pages I have inadvertently allocated.
+	 *
+	 * Ideally I would convert multi-page allocations into single
+	 * page allocations, and add everything to image->dest_pages.
+	 *
+	 * For now it is simpler to just free the pages.
+	 */
+	kimage_free_page_list(&extra_pages);
+
+	return pages;
+}
+
+struct page *firmware_kimage_alloc_control_pages(struct kimage *image,
+							unsigned int order)
+{
+	return kimage_alloc_normal_control_pages(image, order);
+}
+
+static int kimage_add_entry(struct kimage *image, kimage_entry_t entry)
+{
+	if (*image->entry != 0)
+		image->entry++;
+
+	if (image->entry == image->last_entry) {
+		kimage_entry_t *ind_page;
+		struct page *page;
+
+		page = kimage_alloc_page(image, GFP_KERNEL, KIMAGE_NO_DEST);
+		if (!page)
+			return -ENOMEM;
+
+		ind_page = page_address(page);
+		*image->entry = mf_kexec_virt_to_phys(ind_page) | IND_INDIRECTION;
+		image->entry = ind_page;
+		image->last_entry = ind_page +
+				      ((PAGE_SIZE/sizeof(kimage_entry_t)) - 1);
+	}
+	*image->entry = entry;
+	image->entry++;
+	*image->entry = 0;
+
+	return 0;
+}
+
+static int kimage_set_destination(struct kimage *image,
+				   unsigned long destination)
+{
+	int result;
+
+	destination &= PAGE_MASK;
+	result = kimage_add_entry(image, destination | IND_DESTINATION);
+	if (result == 0)
+		image->destination = destination;
+
+	return result;
+}
+
+
+static int kimage_add_page(struct kimage *image, unsigned long page)
+{
+	int result;
+
+	page &= PAGE_MASK;
+	result = kimage_add_entry(image, page | IND_SOURCE);
+	if (result == 0)
+		image->destination += PAGE_SIZE;
+
+	return result;
+}
+
+
+static void kimage_free_extra_pages(struct kimage *image)
+{
+	/* Walk through and free any extra destination pages I may have */
+	kimage_free_page_list(&image->dest_pages);
+
+	/* Walk through and free any unusable pages I have cached */
+	kimage_free_page_list(&image->unuseable_pages);
+
+}
+static void kimage_terminate(struct kimage *image)
+{
+	if (*image->entry != 0)
+		image->entry++;
+
+	*image->entry = IND_DONE;
+}
+
+#define for_each_kimage_entry(image, ptr, entry) \
+	for (ptr = &image->head; (entry = *ptr) && !(entry & IND_DONE); \
+		ptr = (entry & IND_INDIRECTION)? \
+			mf_kexec_phys_to_virt((entry & PAGE_MASK)): ptr +1)
+
+static void kimage_free_entry(kimage_entry_t entry)
+{
+	struct page *page;
+
+	page = mf_kexec_pfn_to_page(entry >> PAGE_SHIFT);
+	mf_kexec_kimage_free_pages(page);
+}
+
+static void kimage_free(struct kimage *image)
+{
+	kimage_entry_t *ptr, entry;
+	kimage_entry_t ind = 0;
+
+	if (!image)
+		return;
+
+	kimage_free_extra_pages(image);
+	for_each_kimage_entry(image, ptr, entry) {
+		if (entry & IND_INDIRECTION) {
+			/* Free the previous indirection page */
+			if (ind & IND_INDIRECTION)
+				kimage_free_entry(ind);
+			/* Save this indirection page until we are
+			 * done with it.
+			 */
+			ind = entry;
+		}
+		else if (entry & IND_SOURCE)
+			kimage_free_entry(entry);
+	}
+	/* Free the final indirection page */
+	if (ind & IND_INDIRECTION)
+		kimage_free_entry(ind);
+
+	/* Handle any machine specific cleanup */
+	mf_kexec_cleanup(image);
+
+	/* Free the kexec control pages... */
+	kimage_free_page_list(&image->control_pages);
+	kfree(image);
+}
+
+static kimage_entry_t *kimage_dst_used(struct kimage *image,
+					unsigned long page)
+{
+	kimage_entry_t *ptr, entry;
+	unsigned long destination = 0;
+
+	for_each_kimage_entry(image, ptr, entry) {
+		if (entry & IND_DESTINATION)
+			destination = entry & PAGE_MASK;
+		else if (entry & IND_SOURCE) {
+			if (page == destination)
+				return ptr;
+			destination += PAGE_SIZE;
+		}
+	}
+
+	return NULL;
+}
+
+static struct page *kimage_alloc_page(struct kimage *image,
+					gfp_t gfp_mask,
+					unsigned long destination)
+{
+	/*
+	 * Here we implement safeguards to ensure that a source page
+	 * is not copied to its destination page before the data on
+	 * the destination page is no longer useful.
+	 *
+	 * To do this we maintain the invariant that a source page is
+	 * either its own destination page, or it is not a
+	 * destination page at all.
+	 *
+	 * That is slightly stronger than required, but the proof
+	 * that no problems will not occur is trivial, and the
+	 * implementation is simply to verify.
+	 *
+	 * When allocating all pages normally this algorithm will run
+	 * in O(N) time, but in the worst case it will run in O(N^2)
+	 * time.   If the runtime is a problem the data structures can
+	 * be fixed.
+	 */
+	struct page *page;
+	unsigned long addr;
+
+	/*
+	 * Walk through the list of destination pages, and see if I
+	 * have a match.
+	 */
+	list_for_each_entry(page, &image->dest_pages, lru) {
+		addr = mf_kexec_page_to_pfn(page) << PAGE_SHIFT;
+		if (addr == destination) {
+			list_del(&page->lru);
+			return page;
+		}
+	}
+	page = NULL;
+	while (1) {
+		kimage_entry_t *old;
+
+		/* Allocate a page, if we run out of memory give up */
+		page = mf_kexec_kimage_alloc_pages(gfp_mask, 0,
+							KEXEC_SOURCE_MEMORY_LIMIT);
+		if (!page)
+			return NULL;
+		/* If the page cannot be used file it away */
+		if (mf_kexec_page_to_pfn(page) >
+				(KEXEC_SOURCE_MEMORY_LIMIT >> PAGE_SHIFT)) {
+			list_add(&page->lru, &image->unuseable_pages);
+			continue;
+		}
+		addr = mf_kexec_page_to_pfn(page) << PAGE_SHIFT;
+
+		/* If it is the destination page we want use it */
+		if (addr == destination)
+			break;
+
+		/* If the page is not a destination page use it */
+		if (!kimage_is_destination_range(image, addr,
+						  addr + PAGE_SIZE))
+			break;
+
+		/*
+		 * I know that the page is someones destination page.
+		 * See if there is already a source page for this
+		 * destination page.  And if so swap the source pages.
+		 */
+		old = kimage_dst_used(image, addr);
+		if (old) {
+			/* If so move it */
+			unsigned long old_addr;
+			struct page *old_page;
+
+			old_addr = *old & PAGE_MASK;
+			old_page = mf_kexec_pfn_to_page(old_addr >> PAGE_SHIFT);
+			copy_highpage(page, old_page);
+			*old = addr | (*old & ~PAGE_MASK);
+
+			/* The old page I have found cannot be a
+			 * destination page, so return it if it's
+			 * gfp_flags honor the ones passed in.
+			 */
+			if (!(gfp_mask & __GFP_HIGHMEM) &&
+			    PageHighMem(old_page)) {
+				mf_kexec_kimage_free_pages(old_page);
+				continue;
+			}
+			addr = old_addr;
+			page = old_page;
+			break;
+		}
+		else {
+			/* Place the page on the destination list I
+			 * will use it later.
+			 */
+			list_add(&page->lru, &image->dest_pages);
+		}
+	}
+
+	return page;
+}
+
+static int kimage_load_normal_segment(struct kimage *image,
+					 struct kexec_segment *segment)
+{
+	unsigned long maddr;
+	unsigned long ubytes, mbytes;
+	int result;
+	unsigned char __user *buf;
+
+	result = 0;
+	buf = segment->buf;
+	ubytes = segment->bufsz;
+	mbytes = segment->memsz;
+	maddr = segment->mem;
+
+	result = kimage_set_destination(image, maddr);
+	if (result < 0)
+		goto out;
+
+	while (mbytes) {
+		struct page *page;
+		char *ptr;
+		size_t uchunk, mchunk;
+
+		page = kimage_alloc_page(image, GFP_HIGHUSER, maddr);
+		if (!page) {
+			result  = -ENOMEM;
+			goto out;
+		}
+		result = kimage_add_page(image, mf_kexec_page_to_pfn(page)
+								<< PAGE_SHIFT);
+		if (result < 0)
+			goto out;
+
+		ptr = kmap(page);
+		/* Start with a clear page */
+		clear_page(ptr);
+		ptr += maddr & ~PAGE_MASK;
+		mchunk = PAGE_SIZE - (maddr & ~PAGE_MASK);
+		if (mchunk > mbytes)
+			mchunk = mbytes;
+
+		uchunk = mchunk;
+		if (uchunk > ubytes)
+			uchunk = ubytes;
+
+		result = copy_from_user(ptr, buf, uchunk);
+		kunmap(page);
+		if (result) {
+			result = -EFAULT;
+			goto out;
+		}
+		ubytes -= uchunk;
+		maddr  += mchunk;
+		buf    += mchunk;
+		mbytes -= mchunk;
+	}
+out:
+	return result;
+}
+
+static int kimage_load_segment(struct kimage *image,
+				struct kexec_segment *segment)
+{
+	return kimage_load_normal_segment(image, segment);
+}
+
+long firmware_sys_kexec_load(unsigned long entry, unsigned long nr_segments,
+				struct kexec_segment __user *segments,
+				unsigned long flags)
+{
+	struct kimage **dest_image, *image = NULL;
+	int result = 0;
+
+	dest_image = &kexec_image;
+	if (flags & KEXEC_ON_CRASH)
+		dest_image = &kexec_crash_image;
+	if (nr_segments > 0) {
+		unsigned long i;
+
+		/* Loading another kernel to reboot into */
+		if ((flags & KEXEC_ON_CRASH) == 0)
+			result = kimage_normal_alloc(&image, entry,
+							nr_segments, segments);
+		/* Loading another kernel to switch to if this one crashes */
+		else if (flags & KEXEC_ON_CRASH) {
+			/* Free any current crash dump kernel before
+			 * we corrupt it.
+			 */
+			mf_kexec_unload(image);
+			kimage_free(xchg(&kexec_crash_image, NULL));
+			result = kimage_crash_alloc(&image, entry,
+						     nr_segments, segments);
+		}
+		if (result)
+			goto out;
+
+		if (flags & KEXEC_PRESERVE_CONTEXT)
+			image->preserve_context = 1;
+		result = mf_kexec_prepare(image);
+		if (result)
+			goto out;
+
+		for (i = 0; i < nr_segments; i++) {
+			result = kimage_load_segment(image, &image->segment[i]);
+			if (result)
+				goto out;
+		}
+		kimage_terminate(image);
+	}
+
+	result = mf_kexec_load(image);
+
+	if (result)
+		goto out;
+
+	/* Install the new kernel, and  Uninstall the old */
+	image = xchg(dest_image, image);
+
+out:
+	mf_kexec_unload(image);
+
+	kimage_free(image);
+
+	return result;
+}
+
+void firmware_crash_kexec(struct pt_regs *regs)
+{
+	struct pt_regs fixed_regs;
+
+	crash_setup_regs(&fixed_regs, regs);
+	crash_save_vmcoreinfo();
+	machine_crash_shutdown(&fixed_regs);
+	mf_kexec(kexec_crash_image);
+}
+
+int firmware_kernel_kexec(void)
+{
+	kernel_restart_prepare(NULL);
+	printk(KERN_EMERG "Starting new kernel\n");
+	mf_kexec_shutdown();
+	mf_kexec(kexec_image);
+
+	return 0;
+}
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 5e4bd78..9f3b6cb 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -38,6 +38,10 @@
 #include <asm/io.h>
 #include <asm/sections.h>
 
+#ifdef CONFIG_KEXEC_FIRMWARE
+bool kexec_use_firmware = false;
+#endif
+
 /* Per cpu memory for storing cpu states in case of system crash. */
 note_buf_t __percpu *crash_notes;
 
@@ -924,7 +928,7 @@ static int kimage_load_segment(struct kimage *image,
  *   the devices in a consistent state so a later kernel can
  *   reinitialize them.
  *
- * - A machine specific part that includes the syscall number
+ * - A machine/firmware specific part that includes the syscall number
  *   and the copies the image to it's final destination.  And
  *   jumps into the image at entry.
  *
@@ -978,6 +982,17 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments,
 	if (!mutex_trylock(&kexec_mutex))
 		return -EBUSY;
 
+#ifdef CONFIG_KEXEC_FIRMWARE
+	if (kexec_use_firmware) {
+		result = firmware_sys_kexec_load(entry, nr_segments,
+							segments, flags);
+
+		mutex_unlock(&kexec_mutex);
+
+		return result;
+	}
+#endif
+
 	dest_image = &kexec_image;
 	if (flags & KEXEC_ON_CRASH)
 		dest_image = &kexec_crash_image;
@@ -1091,10 +1106,17 @@ void crash_kexec(struct pt_regs *regs)
 		if (kexec_crash_image) {
 			struct pt_regs fixed_regs;
 
-			crash_setup_regs(&fixed_regs, regs);
-			crash_save_vmcoreinfo();
-			machine_crash_shutdown(&fixed_regs);
-			machine_kexec(kexec_crash_image);
+#ifdef CONFIG_KEXEC_FIRMWARE
+			if (kexec_use_firmware)
+				firmware_crash_kexec(regs);
+			else
+#endif
+			{
+				crash_setup_regs(&fixed_regs, regs);
+				crash_save_vmcoreinfo();
+				machine_crash_shutdown(&fixed_regs);
+				machine_kexec(kexec_crash_image);
+			}
 		}
 		mutex_unlock(&kexec_mutex);
 	}
@@ -1132,6 +1154,13 @@ int crash_shrink_memory(unsigned long new_size)
 
 	mutex_lock(&kexec_mutex);
 
+#ifdef CONFIG_KEXEC_FIRMWARE
+	if (kexec_use_firmware) {
+		ret = -ENOSYS;
+		goto unlock;
+	}
+#endif
+
 	if (kexec_crash_image) {
 		ret = -ENOENT;
 		goto unlock;
@@ -1536,6 +1565,13 @@ int kernel_kexec(void)
 		goto Unlock;
 	}
 
+#ifdef CONFIG_KEXEC_FIRMWARE
+	if (kexec_use_firmware) {
+		error = firmware_kernel_kexec();
+		goto Unlock;
+	}
+#endif
+
 #ifdef CONFIG_KEXEC_JUMP
 	if (kexec_image->preserve_context) {
 		lock_system_sleep();
-- 
1.5.6.5


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[PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Daniel Kiper]

Some implementations (e.g. Xen PVOPS) could not use part of identity page table
to construct transition page table. It means that they require separate PUDs,
PMDs and PTEs for virtual and physical (identity) mapping. To satisfy that
requirement add extra pointer to PGD, PUD, PMD and PTE and align existing code.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 arch/x86/include/asm/kexec.h       |   10 +++++++---
 arch/x86/kernel/machine_kexec_64.c |   12 ++++++------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index 6080d26..cedd204 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -157,9 +157,13 @@ struct kimage_arch {
 };
 #else
 struct kimage_arch {
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
+	pgd_t *pgd;
+	pud_t *pud0;
+	pud_t *pud1;
+	pmd_t *pmd0;
+	pmd_t *pmd1;
+	pte_t *pte0;
+	pte_t *pte1;
 };
 #endif
 
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index b3ea9db..976e54b 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -137,9 +137,9 @@ out:
 
 static void free_transition_pgtable(struct kimage *image)
 {
-	free_page((unsigned long)image->arch.pud);
-	free_page((unsigned long)image->arch.pmd);
-	free_page((unsigned long)image->arch.pte);
+	free_page((unsigned long)image->arch.pud0);
+	free_page((unsigned long)image->arch.pmd0);
+	free_page((unsigned long)image->arch.pte0);
 }
 
 static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
@@ -157,7 +157,7 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
 		pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
 		if (!pud)
 			goto err;
-		image->arch.pud = pud;
+		image->arch.pud0 = pud;
 		set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE));
 	}
 	pud = pud_offset(pgd, vaddr);
@@ -165,7 +165,7 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
 		pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
 		if (!pmd)
 			goto err;
-		image->arch.pmd = pmd;
+		image->arch.pmd0 = pmd;
 		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
 	}
 	pmd = pmd_offset(pud, vaddr);
@@ -173,7 +173,7 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
 		pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
 		if (!pte)
 			goto err;
-		image->arch.pte = pte;
+		image->arch.pte0 = pte;
 		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
 	}
 	pte = pte_offset_kernel(pmd, vaddr);
-- 
1.5.6.5


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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[H. Peter Anvin]

Hmm... this code is being redone at the moment... this might conflict.

Daniel Kiper <daniel.kiper@oracle.com> wrote:

>Some implementations (e.g. Xen PVOPS) could not use part of identity
>page table
>to construct transition page table. It means that they require separate
>PUDs,
>PMDs and PTEs for virtual and physical (identity) mapping. To satisfy
>that
>requirement add extra pointer to PGD, PUD, PMD and PTE and align
>existing code.
>
>Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
>---
> arch/x86/include/asm/kexec.h       |   10 +++++++---
> arch/x86/kernel/machine_kexec_64.c |   12 ++++++------
> 2 files changed, 13 insertions(+), 9 deletions(-)
>
>diff --git a/arch/x86/include/asm/kexec.h
>b/arch/x86/include/asm/kexec.h
>index 6080d26..cedd204 100644
>--- a/arch/x86/include/asm/kexec.h
>+++ b/arch/x86/include/asm/kexec.h
>@@ -157,9 +157,13 @@ struct kimage_arch {
> };
> #else
> struct kimage_arch {
>-	pud_t *pud;
>-	pmd_t *pmd;
>-	pte_t *pte;
>+	pgd_t *pgd;
>+	pud_t *pud0;
>+	pud_t *pud1;
>+	pmd_t *pmd0;
>+	pmd_t *pmd1;
>+	pte_t *pte0;
>+	pte_t *pte1;
> };
> #endif
> 
>diff --git a/arch/x86/kernel/machine_kexec_64.c
>b/arch/x86/kernel/machine_kexec_64.c
>index b3ea9db..976e54b 100644
>--- a/arch/x86/kernel/machine_kexec_64.c
>+++ b/arch/x86/kernel/machine_kexec_64.c
>@@ -137,9 +137,9 @@ out:
> 
> static void free_transition_pgtable(struct kimage *image)
> {
>-	free_page((unsigned long)image->arch.pud);
>-	free_page((unsigned long)image->arch.pmd);
>-	free_page((unsigned long)image->arch.pte);
>+	free_page((unsigned long)image->arch.pud0);
>+	free_page((unsigned long)image->arch.pmd0);
>+	free_page((unsigned long)image->arch.pte0);
> }
> 
> static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
>@@ -157,7 +157,7 @@ static int init_transition_pgtable(struct kimage
>*image, pgd_t *pgd)
> 		pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
> 		if (!pud)
> 			goto err;
>-		image->arch.pud = pud;
>+		image->arch.pud0 = pud;
> 		set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE));
> 	}
> 	pud = pud_offset(pgd, vaddr);
>@@ -165,7 +165,7 @@ static int init_transition_pgtable(struct kimage
>*image, pgd_t *pgd)
> 		pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
> 		if (!pmd)
> 			goto err;
>-		image->arch.pmd = pmd;
>+		image->arch.pmd0 = pmd;
> 		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
> 	}
> 	pmd = pmd_offset(pud, vaddr);
>@@ -173,7 +173,7 @@ static int init_transition_pgtable(struct kimage
>*image, pgd_t *pgd)
> 		pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
> 		if (!pte)
> 			goto err;
>-		image->arch.pte = pte;
>+		image->arch.pte0 = pte;
> 		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
> 	}
> 	pte = pte_offset_kernel(pmd, vaddr);

-- 
Sent from my mobile phone. Please excuse brevity and lack of formatting.

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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Jan Beulich]

>>> On 27.12.12 at 03:18, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> Some implementations (e.g. Xen PVOPS) could not use part of identity page 
> table
> to construct transition page table. It means that they require separate 
> PUDs,
> PMDs and PTEs for virtual and physical (identity) mapping. To satisfy that
> requirement add extra pointer to PGD, PUD, PMD and PTE and align existing 
> code.

So you keep posting this despite it having got pointed out on each
earlier submission that this is unnecessary, proven by the fact that
the non-pvops Xen kernels can get away without it. Why?

Jan


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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Daniel Kiper]

On Thu, Jan 03, 2013 at 09:34:55AM +0000, Jan Beulich wrote:
> >>> On 27.12.12 at 03:18, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> > Some implementations (e.g. Xen PVOPS) could not use part of identity page table
> > to construct transition page table. It means that they require separate PUDs,
> > PMDs and PTEs for virtual and physical (identity) mapping. To satisfy that
> > requirement add extra pointer to PGD, PUD, PMD and PTE and align existing
> > code.
>
> So you keep posting this despite it having got pointed out on each
> earlier submission that this is unnecessary, proven by the fact that
> the non-pvops Xen kernels can get away without it. Why?

Sorry but I forgot to reply for your email last time.

I am still not convinced. I have tested SUSE kernel itself and it does not work.
Maybe I missed something but... Please check arch/x86/kernel/machine_kexec_64.c:init_transition_pgtable()

I can see:

vaddr = (unsigned long)relocate_kernel;

and later:

pgd += pgd_index(vaddr);
...

It is wrong. relocate_kernel() virtual address in Xen is different
than its virtual address in Linux Kernel. That is why transition
page table could not be established in Linux Kernel and so on...
How does this work in SUSE? I do not have an idea.

I am happy to fix that but whatever fix for it is
I would like to be sure that it works.

Daniel

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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Jan Beulich]

>>> On 04.01.13 at 16:15, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> On Thu, Jan 03, 2013 at 09:34:55AM +0000, Jan Beulich wrote:
>> >>> On 27.12.12 at 03:18, Daniel Kiper <daniel.kiper@oracle.com> wrote:
>> > Some implementations (e.g. Xen PVOPS) could not use part of identity page 
> table
>> > to construct transition page table. It means that they require separate 
> PUDs,
>> > PMDs and PTEs for virtual and physical (identity) mapping. To satisfy that
>> > requirement add extra pointer to PGD, PUD, PMD and PTE and align existing
>> > code.
>>
>> So you keep posting this despite it having got pointed out on each
>> earlier submission that this is unnecessary, proven by the fact that
>> the non-pvops Xen kernels can get away without it. Why?
> 
> Sorry but I forgot to reply for your email last time.
> 
> I am still not convinced. I have tested SUSE kernel itself and it does not 
> work.
> Maybe I missed something but... Please check 
> arch/x86/kernel/machine_kexec_64.c:init_transition_pgtable()
> 
> I can see:
> 
> vaddr = (unsigned long)relocate_kernel;
> 
> and later:
> 
> pgd += pgd_index(vaddr);
> ...

I think that mapping is simply irrelevant, as the code at
relocate_kernel gets copied to the control page and
invoked there (other than in the native case, where
relocate_kernel() gets invoked directly).

Jan

> It is wrong. relocate_kernel() virtual address in Xen is different
> than its virtual address in Linux Kernel. That is why transition
> page table could not be established in Linux Kernel and so on...
> How does this work in SUSE? I do not have an idea.
> 
> I am happy to fix that but whatever fix for it is
> I would like to be sure that it works.
> 
> Daniel




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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Daniel Kiper]

On Fri, Jan 04, 2013 at 04:12:32PM +0000, Jan Beulich wrote:
> >>> On 04.01.13 at 16:15, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> > On Thu, Jan 03, 2013 at 09:34:55AM +0000, Jan Beulich wrote:
> >> >>> On 27.12.12 at 03:18, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> >> > Some implementations (e.g. Xen PVOPS) could not use part of identity page table
> >> > to construct transition page table. It means that they require separate PUDs,
> >> > PMDs and PTEs for virtual and physical (identity) mapping. To satisfy that
> >> > requirement add extra pointer to PGD, PUD, PMD and PTE and align existing
> >> > code.
> >>
> >> So you keep posting this despite it having got pointed out on each
> >> earlier submission that this is unnecessary, proven by the fact that
> >> the non-pvops Xen kernels can get away without it. Why?
> >
> > Sorry but I forgot to reply for your email last time.
> >
> > I am still not convinced. I have tested SUSE kernel itself and it does not work.
> > Maybe I missed something but... Please check
> > arch/x86/kernel/machine_kexec_64.c:init_transition_pgtable()
> >
> > I can see:
> >
> > vaddr = (unsigned long)relocate_kernel;
> >
> > and later:
> >
> > pgd += pgd_index(vaddr);
> > ...
>
> I think that mapping is simply irrelevant, as the code at
> relocate_kernel gets copied to the control page and
> invoked there (other than in the native case, where
> relocate_kernel() gets invoked directly).

Right, so where is virtual mapping of control page established?
I could not find relevant code in SLES kernel which does that.

Daniel

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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Jan Beulich]

>>> On 04.01.13 at 18:25, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> Right, so where is virtual mapping of control page established?
> I could not find relevant code in SLES kernel which does that.

In the hypervisor (xen/arch/x86/machine_kexec.c:machine_kexec_load()).
xen/arch/x86/machine_kexec.c:machine_kexec() then simply uses
image->page_list[1].

Jan


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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Daniel Kiper]

On Mon, Jan 07, 2013 at 09:48:20AM +0000, Jan Beulich wrote:
> >>> On 04.01.13 at 18:25, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> > Right, so where is virtual mapping of control page established?
> > I could not find relevant code in SLES kernel which does that.
>
> In the hypervisor (xen/arch/x86/machine_kexec.c:machine_kexec_load()).
> xen/arch/x86/machine_kexec.c:machine_kexec() then simply uses
> image->page_list[1].

This (xen/arch/x86/machine_kexec.c:machine_kexec_load()) maps relevant
page (allocated earlier by dom0) in hypervisor fixmap area. However,
it does not make relevant mapping in transition page table which
leads to crash when %cr3 is switched from Xen page table to
transition page table.

Daniel

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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Jan Beulich]

>>> On 07.01.13 at 13:52, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> On Mon, Jan 07, 2013 at 09:48:20AM +0000, Jan Beulich wrote:
>> >>> On 04.01.13 at 18:25, Daniel Kiper <daniel.kiper@oracle.com> wrote:
>> > Right, so where is virtual mapping of control page established?
>> > I could not find relevant code in SLES kernel which does that.
>>
>> In the hypervisor (xen/arch/x86/machine_kexec.c:machine_kexec_load()).
>> xen/arch/x86/machine_kexec.c:machine_kexec() then simply uses
>> image->page_list[1].
> 
> This (xen/arch/x86/machine_kexec.c:machine_kexec_load()) maps relevant
> page (allocated earlier by dom0) in hypervisor fixmap area. However,
> it does not make relevant mapping in transition page table which
> leads to crash when %cr3 is switched from Xen page table to
> transition page table.

That indeed could explain _random_ failures - the fixmap entries
get created with _PAGE_GLOBAL set, i.e. don't get flushed with
the CR3 write unless CR4.PGE is clear.

And I don't see how your allocation of intermediate page tables
would help: You wouldn't know where the mapping of the control
page lives until you're actually in the early relocate_kernel code.
Or was it that what distinguishes your cloned code from the
native original?

Jan


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Re: [PATCH v3 02/11] x86/kexec: Add extra pointers to transition page table PGD, PUD, PMD and PTE

[Daniel Kiper]

On Mon, Jan 07, 2013 at 01:05:10PM +0000, Jan Beulich wrote:
> >>> On 07.01.13 at 13:52, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> > On Mon, Jan 07, 2013 at 09:48:20AM +0000, Jan Beulich wrote:
> >> >>> On 04.01.13 at 18:25, Daniel Kiper <daniel.kiper@oracle.com> wrote:
> >> > Right, so where is virtual mapping of control page established?
> >> > I could not find relevant code in SLES kernel which does that.
> >>
> >> In the hypervisor (xen/arch/x86/machine_kexec.c:machine_kexec_load()).
> >> xen/arch/x86/machine_kexec.c:machine_kexec() then simply uses
> >> image->page_list[1].
> >
> > This (xen/arch/x86/machine_kexec.c:machine_kexec_load()) maps relevant
> > page (allocated earlier by dom0) in hypervisor fixmap area. However,
> > it does not make relevant mapping in transition page table which
> > leads to crash when %cr3 is switched from Xen page table to
> > transition page table.
>
> That indeed could explain _random_ failures - the fixmap entries
> get created with _PAGE_GLOBAL set, i.e. don't get flushed with
> the CR3 write unless CR4.PGE is clear.

This does not matter. As I stated earlier virtual mapping is wrong.
relocate_kernel() is mapped at its virtual address in Linux kernel
instead of control page at its virtual address in Xen hypervisor.
I tested SLES kernel once again. It does not work.

> And I don't see how your allocation of intermediate page tables
> would help: You wouldn't know where the mapping of the control
> page lives until you're actually in the early relocate_kernel code.

Right. Allocation itself is not a solution for this problem.
It should be acompanied by code which establishes transition
page table in relocate_kernel() (which is later copied
to control page, i.e. code of relocate_kernel()).

> Or was it that what distinguishes your cloned code from the
> native original?

No, my code is based on native original.
There are some implementation differences.

Daniel

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