On Thu, Feb 21, 2013 at 05:48:11PM +0000, David Vrabel wrote:
> From: David Vrabel <david.vrabel at citrix.com>
>
> In the existing kexec hypercall, the load and unload ops depend on
> internals of the Linux kernel (the page list and code page provided by
> the kernel). The code page is used to transition between Xen context
> and the image so using kernel code doesn't make sense and will not
> work for PVH guests.
>
> Add replacement KEXEC_CMD_kexec_load and KEXEC_CMD_kexec_unload ops
> that no longer require a code page to be provided by the guest -- Xen
> now provides the code for calling the image directly.
>
> The new load op looks similar to the Linux kexec_load system call and
> allows the guest to provide the image data to be loaded. The guest
> specifies the architecture of the image which may be a 32-bit subarch
> of the hypervisor's architecture (i.e., an EM_386 image on an
> EM_X86_64 hypervisor).
>
> The toolstack can now load images without kernel involvement. This is
> required for supporting kexec when using a dom0 with an upstream
> kernel.
>
> Crash images are copied directly into the crash region on load.
> Default images are copied into Xen heap pages and a list of source and
> destination machine addresses is created. This is list is used in
> kexec_reloc() to relocate the image to its destination.
>
> The old load and unload sub-ops are still available (as
> KEXEC_CMD_load_v1 and KEXEC_CMD_unload_v1) and are implemented on top
> of the new infrastructure.
>
> Signed-off-by: David Vrabel <david.vrabel at citrix.com>
[...]
> diff --git a/xen/arch/x86/x86_64/kexec_reloc.S b/xen/arch/x86/x86_64/kexec_reloc.S
> new file mode 100644
> index 0000000..e68842c
> --- /dev/null
> +++ b/xen/arch/x86/x86_64/kexec_reloc.S
> @@ -0,0 +1,229 @@
> +/*
> + * Relocate a kexec_image to its destination and call it.
> + *
> + * Copyright (C) 2013 Citrix Systems R&D Ltd.
> + *
> + * Portions derived from Linux's arch/x86/kernel/relocate_kernel_64.S.
> + *
> + * Copyright (C) 2002-2005 Eric Biederman <ebiederm at xmission.com>
> + *
> + * This source code is licensed under the GNU General Public License,
> + * Version 2. See the file COPYING for more details.
> + */
> +#include <xen/config.h>
> +
> +#include <asm/asm_defns.h>
> +#include <asm/msr.h>
> +#include <asm/page.h>
> +#include <asm/machine_kexec.h>
> +
> +/* The unrelocated physical address of a symbol. */
> +#define SYM_PHYS(sym) ((sym) - __XEN_VIRT_START)
> +
> +/* Load physical address of symbol into register and relocate it. */
> +#define RELOCATE_SYM(sym,reg) mov $SYM_PHYS(sym), reg ; \
> + add xen_phys_start(%rip), reg
> +
> +#define DBG(c) \
> +1: mov $0x3f8+5, %dx ; \
> + inb %dx, %al ; \
> + test $0x20, %al ; \
> + je 1b ; \
> + mov $0x3f8, %dx ; \
> + mov $c, %al ; \
> + outb %al, %dx ;
> +
> + .text
> + .align PAGE_SIZE
> + .code64
> +
> +ENTRY(kexec_reloc)
> + /* %rdi - code_page maddr */
> + /* %rsi - page table maddr */
> + /* %rdx - indirection page maddr */
> + /* %rcx - entry maddr */
> + /* %r8 - flags */
> +
> + mov %rdx, %rbx
> +
> + DBG('A')
> +
> + /* Setup stack. */
> + RELOCATE_SYM(reloc_stack, %rax)
> + mov %rax, %rsp
> +
> + DBG('B')
> +
> + wbinvd
> + movq %cr4, %rax
> + andq $~(X86_CR4_PGE|X86_CR4_PCE|X86_CR4_MCE), %rax
> + movq %rax, %cr4
> +
> + /* Load reloc page table. */
> + movq %rsi, %cr3
> +
> + DBG('C')
> +
> + /* Jump to identity mapped code. */
> + movq %rdi, %r9
> + addq $(identity_mapped - kexec_reloc), %r9
> +
> + DBG('D')
> +
> + jmp *%r9
> +
> +identity_mapped:
> + DBG('E')
> +
> + pushq %rcx
> + pushq %rbx
> + pushq %rsi
> + pushq %rdi
> +
> + movq %rbx, %rdi
> + call swap_pages
> +
> + popq %rdi
> + popq %rsi
> + popq %rbx
> + popq %rcx
> +
> + DBG('F')
> +
> + /* Need to switch to 32-bit mode? */
> + testq $KEXEC_RELOC_FLAG_COMPAT, %r8
> + jnz call_32_bit
Why do you need that? This is not needed because purgatory code
from kexec-tools always switches to 32-bit mode. Please check
kexec-tools/purgatory/arch/x86_64/entry64.S.
Daniel
