Re: [Xen-devel] [PATCH 4/4] kexec/xen: directly load images images into Xen

Don Slutz
2013-11-07T20:39:45Z

For what it is worth.

Reviewed-by: Don Slutz <dslutz@verizon.com>
-Don Slutz

On 11/06/13 09:55, David Vrabel wrote:
> From: David Vrabel <david.vrabel@citrix.com>
>
> Xen 4.4 has an improvided kexec hypercall ABI that allows images to be
> loaded and executed without any kernel involvement. Use the API
> provided by libxc to load images when running in a Xen guest.
>
> Support for loading images via the kexec_load syscall in non-upstream
> ("classic") Xen kernels is no longer supported.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
> ---
> kexec/Makefile | 1 +
> kexec/arch/i386/crashdump-x86.c | 20 +++++-
> kexec/crashdump-xen.c | 34 ++++++++++
> kexec/crashdump.h | 3 +-
> kexec/kexec-xen.c | 139 +++++++++++++++++++++++++++++++++++++++
> kexec/kexec.c | 24 +++++--
> kexec/kexec.h | 5 ++
> 7 files changed, 218 insertions(+), 8 deletions(-)
> create mode 100644 kexec/kexec-xen.c
>
> diff --git a/kexec/Makefile b/kexec/Makefile
> index 8a6138d..dc9dab1 100644
> --- a/kexec/Makefile
> +++ b/kexec/Makefile
> @@ -25,6 +25,7 @@ KEXEC_SRCS_base += kexec/phys_arch.c
> KEXEC_SRCS_base += kexec/kernel_version.c
> KEXEC_SRCS_base += kexec/lzma.c
> KEXEC_SRCS_base += kexec/zlib.c
> +KEXEC_SRCS_base += kexec/kexec-xen.c
>
> KEXEC_GENERATED_SRCS += $(PURGATORY_HEX_C)
>
> diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c
> index 7aa5a12..85f3a87 100644
> --- a/kexec/arch/i386/crashdump-x86.c
> +++ b/kexec/arch/i386/crashdump-x86.c
> @@ -990,8 +990,24 @@ static int crashkernel_mem_callback(void *UNUSED(data), int nr,
>
> int is_crashkernel_mem_reserved(void)
> {
> - crash_reserved_mem_nr = kexec_iomem_for_each_line("Crash kernel\n",
> - crashkernel_mem_callback, NULL);
> + int ret;
> +
> + if (xen_present()) {
> + uint64_t start, end;
> +
> + ret = xen_get_crashkernel_region(&start, &end);
> + if (ret < 0)
> + return 0;
> +
> + crash_reserved_mem[0].start = start;
> + crash_reserved_mem[0].end = end;
> + crash_reserved_mem[0].type = RANGE_RAM;
> + crash_reserved_mem_nr = 1;
> + } else {
> + ret = kexec_iomem_for_each_line("Crash kernel\n",
> + crashkernel_mem_callback, NULL);
> + crash_reserved_mem_nr = ret;
> + }
>
> return !!crash_reserved_mem_nr;
> }
> diff --git a/kexec/crashdump-xen.c b/kexec/crashdump-xen.c
> index 79b68e0..60594f6 100644
> --- a/kexec/crashdump-xen.c
> +++ b/kexec/crashdump-xen.c
> @@ -252,3 +252,37 @@ int xen_get_note(int cpu, uint64_t *addr, uint64_t *len)
>
> return 0;
> }
> +
> +#ifdef HAVE_LIBXENCTRL
> +int xen_get_crashkernel_region(uint64_t *start, uint64_t *end)
> +{
> + uint64_t size;
> + xc_interface *xc;
> + int rc = -1;
> +
> + xc = xc_interface_open(NULL, NULL, 0);
> + if (!xc) {
> + fprintf(stderr, "failed to open xen control interface.\n");
> + goto out;
> + }
> +
> + rc = xc_kexec_get_range(xc, KEXEC_RANGE_MA_CRASH, 0, &size, start);
> + if (rc < 0) {
> + fprintf(stderr, "failed to get crash region from hypervisor.\n");
> + goto out_close;
> + }
> +
> + *end = *start + size - 1;
> +
> +out_close:
> + xc_interface_close(xc);
> +
> +out:
> + return rc;
> +}
> +#else
> +int xen_get_crashkernel_region(uint64_t *start, uint64_t *end)
> +{
> + return -1;
> +}
> +#endif
> diff --git a/kexec/crashdump.h b/kexec/crashdump.h
> index 0f7c2ea..95f1f0c 100644
> --- a/kexec/crashdump.h
> +++ b/kexec/crashdump.h
> @@ -1,6 +1,7 @@
> #ifndef CRASHDUMP_H
> #define CRASHDUMP_H
>
> +int get_crashkernel_region(uint64_t *start, uint64_t *end);
> extern int get_crash_notes_per_cpu(int cpu, uint64_t *addr, uint64_t *len);
> extern int get_kernel_vmcoreinfo(uint64_t *addr, uint64_t *len);
> extern int get_xen_vmcoreinfo(uint64_t *addr, uint64_t *len);
> @@ -56,9 +57,9 @@ unsigned long crash_architecture(struct crash_elf_info *elf_info);
> unsigned long phys_to_virt(struct crash_elf_info *elf_info,
> unsigned long paddr);
>
> -int xen_present(void);
> unsigned long xen_architecture(struct crash_elf_info *elf_info);
> int xen_get_nr_phys_cpus(void);
> int xen_get_note(int cpu, uint64_t *addr, uint64_t *len);
> +int xen_get_crashkernel_region(uint64_t *start, uint64_t *end);
>
> #endif /* CRASHDUMP_H */
> diff --git a/kexec/kexec-xen.c b/kexec/kexec-xen.c
> new file mode 100644
> index 0000000..77f65c0
> --- /dev/null
> +++ b/kexec/kexec-xen.c
> @@ -0,0 +1,139 @@
> +#define _GNU_SOURCE
> +#include <stdio.h>
> +#include <string.h>
> +#include <stdlib.h>
> +#include <elf.h>
> +#include "kexec.h"
> +#include "kexec-syscall.h"
> +#include "crashdump.h"
> +
> +#include "config.h"
> +
> +#ifdef HAVE_LIBXENCTRL
> +#include <xenctrl.h>
> +
> +#include "crashdump.h"
> +
> +int xen_kexec_load(struct kexec_info *info)
> +{
> + uint32_t nr_segments = info->nr_segments;
> + struct kexec_segment *segments = info->segment;
> + xc_interface *xch;
> + xc_hypercall_buffer_array_t *array = NULL;
> + uint8_t type;
> + uint8_t arch;
> + xen_kexec_segment_t *xen_segs;
> + int s;
> + int ret = -1;
> +
> + xch = xc_interface_open(NULL, NULL, 0);
> + if (!xch)
> + return -1;
> +
> + xen_segs = calloc(nr_segments + 1, sizeof(*xen_segs));
> + if (!xen_segs)
> + goto out;
> +
> + array = xc_hypercall_buffer_array_create(xch, nr_segments);
> + if (array == NULL)
> + goto out;
> +
> + for (s = 0; s < nr_segments; s++) {
> + DECLARE_HYPERCALL_BUFFER(void, seg_buf);
> +
> + seg_buf = xc_hypercall_buffer_array_alloc(xch, array, s,
> + seg_buf, segments[s].bufsz);
> + if (seg_buf == NULL)
> + goto out;
> + memcpy(seg_buf, segments[s].buf, segments[s].bufsz);
> +
> + set_xen_guest_handle(xen_segs[s].buf.h, seg_buf);
> + xen_segs[s].buf_size = segments[s].bufsz;
> + xen_segs[s].dest_maddr = (uint64_t)segments[s].mem;
> + xen_segs[s].dest_size = segments[s].memsz;
> + }
> +
> + /*
> + * Ensure 0 - 1 MiB is mapped and accessible by the image.
> + *
> + * This allows access to the VGA memory and the region
> + * purgatory copies in the crash case.
> + */
> + set_xen_guest_handle(xen_segs[s].buf.h, HYPERCALL_BUFFER_NULL);
> + xen_segs[s].buf_size = 0;
> + xen_segs[s].dest_maddr = 0;
> + xen_segs[s].dest_size = 1 * 1024 * 1024;
> + nr_segments++;
> +
> + type = (info->kexec_flags & KEXEC_ON_CRASH) ? KEXEC_TYPE_CRASH
> + : KEXEC_TYPE_DEFAULT;
> +
> + arch = (info->kexec_flags & KEXEC_ARCH_MASK) >> 16;
> +#if defined(_i386__) || defined(__x86_64__)
> + if (!arch)
> + arch = EM_386;
> +#endif
> +
> + ret = xc_kexec_load(xch, type, arch, (uint64_t)info->entry,
> + nr_segments, xen_segs);
> +
> +out:
> + xc_hypercall_buffer_array_destroy(xch, array);
> + free(xen_segs);
> + xc_interface_close(xch);
> +
> + return ret;
> +}
> +
> +int xen_kexec_unload(uint64_t kexec_flags)
> +{
> + xc_interface *xch;
> + uint8_t type;
> + int ret;
> +
> + xch = xc_interface_open(NULL, NULL, 0);
> + if (!xch)
> + return -1;
> +
> + type = (kexec_flags & KEXEC_ON_CRASH) ? KEXEC_TYPE_CRASH
> + : KEXEC_TYPE_DEFAULT;
> +
> + ret = xc_kexec_unload(xch, type);
> +
> + xc_interface_close(xch);
> +
> + return ret;
> +}
> +
> +void xen_kexec_exec(void)
> +{
> + xc_interface *xch;
> +
> + xch = xc_interface_open(NULL, NULL, 0);
> + if (!xch)
> + return;
> +
> + xc_kexec_exec(xch, KEXEC_TYPE_DEFAULT);
> +
> + xc_interface_close(xch);
> +}
> +
> +#else /* ! HAVE_LIBXENCTRL */
> +
> +int xen_kexec_load(uint64_t entry,
> + uint32_t nr_segments, struct kexec_segment *segments,
> + uint64_t kexec_flags)
> +{
> + return -1;
> +}
> +
> +int xen_kexec_unload(uin64_t kexec_flags);
> +{
> + return -1;
> +}
> +
> +void xen_kexec_exec(void)
> +{
> +}
> +
> +#endif
> diff --git a/kexec/kexec.c b/kexec/kexec.c
> index 2ce570f..9dc3fa4 100644
> --- a/kexec/kexec.c
> +++ b/kexec/kexec.c
> @@ -764,8 +764,12 @@ static int my_load(const char *type, int fileind, int argc, char **argv,
> if (kexec_debug)
> print_segments(stderr, &info);
>
> - result = kexec_load(
> - info.entry, info.nr_segments, info.segment, info.kexec_flags);
> + if (xen_present())
> + result = xen_kexec_load(&info);
> + else
> + result = kexec_load(info.entry,
> + info.nr_segments, info.segment,
> + info.kexec_flags);
> if (result != 0) {
> /* The load failed, print some debugging information */
> fprintf(stderr, "kexec_load failed: %s\n",
> @@ -789,10 +793,13 @@ static int k_unload (unsigned long kexec_flags)
> }
> kexec_flags |= native_arch;
>
> - result = kexec_load(NULL, 0, NULL, kexec_flags);
> + if (xen_present())
> + result = xen_kexec_unload(kexec_flags);
> + else
> + result = kexec_load(NULL, 0, NULL, kexec_flags);
> if (result != 0) {
> /* The unload failed, print some debugging information */
> - fprintf(stderr, "kexec_load (0 segments) failed: %s\n",
> + fprintf(stderr, "kexec unload failed: %s\n",
> strerror(errno));
> }
> return result;
> @@ -823,7 +830,10 @@ static int my_shutdown(void)
> */
> static int my_exec(void)
> {
> - reboot(LINUX_REBOOT_CMD_KEXEC);
> + if (xen_present())
> + xen_kexec_exec();
> + else
> + reboot(LINUX_REBOOT_CMD_KEXEC);
> /* I have failed if I make it here */
> fprintf(stderr, "kexec failed: %s\n",
> strerror(errno));
> @@ -928,6 +938,10 @@ static int kexec_loaded(void)
> char *p;
> char line[3];
>
> + /* No way to tell if an image is loaded under Xen, assume it is. */
> + if (xen_present())
> + return 1;
> +
> fp = fopen("/sys/kernel/kexec_loaded", "r");
> if (fp == NULL)
> return -1;
> diff --git a/kexec/kexec.h b/kexec/kexec.h
> index 2904e03..c8be4a5 100644
> --- a/kexec/kexec.h
> +++ b/kexec/kexec.h
> @@ -289,4 +289,9 @@ const char * proc_iomem(void);
>
> char *concat_cmdline(const char *base, const char *append);
>
> +int xen_present(void);
> +int xen_kexec_load(struct kexec_info *info);
> +int xen_kexec_unload(uint64_t kexec_flags);
> +void xen_kexec_exec(void);
> +
> #endif /* KEXEC_H */