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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 5/8] kexec: extend hypercall with improved load/unload ops
On Mon, Apr 08, 2013 at 07:59:50PM +0100, David Vrabel wrote:
> From: David Vrabel <david.vrabel@xxxxxxxxxx>
>
> 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 domheap 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@xxxxxxxxxx>
[...]
> 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..9d09c35
> --- /dev/null
> +++ b/xen/arch/x86/x86_64/kexec_reloc.S
> @@ -0,0 +1,215 @@
> +/*
> + * 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@xxxxxxxxxxxx>
> + *
> + * 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
> +
> + .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
movq?
> +
> + /* Setup stack. */
> + RELOCATE_SYM(reloc_stack, %rax)
> + mov %rax, %rsp
Ditto?
> +
> + /* Load reloc page table. */
> + movq %rsi, %cr3
...because at least you use movq here...
...etc...
> +
> + /* Jump to identity mapped code. */
> + movq %rdi, %r9
> + addq $(identity_mapped - kexec_reloc), %r9
> +
> + jmp *%r9
jmpq *(identity_mapped - kexec_reloc)(%rdi)
> +
> +identity_mapped:
> + pushq %rcx
> + pushq %rbx
> + pushq %rsi
> + pushq %rdi
> +
> + /*
> + * Set cr0 to a known state:
> + * - Paging enabled
> + * - Alignment check disabled
> + * - Write protect disabled
> + * - No task switch
> + * - Don't do FP software emulation.
> + * - Proctected mode enabled
> + */
> + movq %cr0, %rax
> + andq $~(X86_CR0_AM | X86_CR0_WP | X86_CR0_TS | X86_CR0_EM), %rax
> + orl $(X86_CR0_PG | X86_CR0_PE), %eax
> + movq %rax, %cr0
> +
> + /*
> + * Set cr4 to a known state:
> + * - physical address extension enabled
> + */
> + movq $X86_CR4_PAE, %rax
> + movq %rax, %cr4
> +
> + movq %rbx, %rdi
> + call relocate_pages
> +
> + popq %rdi
> + popq %rsi
> + popq %rbx
> + popq %rcx
> +
> + /* Need to switch to 32-bit mode? */
> + testq $KEXEC_RELOC_FLAG_COMPAT, %r8
> + jnz call_32_bit
> +
> +call_64_bit:
> + /* Call the image entry point. This should never return. */
> + call *%rcx
> + ud2
> +
> +call_32_bit:
> + /* Relocate compatibility mode entry point address. */
> + movl %edi, %eax
> + addl $(compatibility_mode - kexec_reloc), %eax
leal (compatibility_mode - kexec_reloc)(%edi), %eax
> + movl %eax, compatibility_mode_far(%rip)
> +
> + /* setup idt */
> + lidt compat_mode_idt(%rip)
> +
> + /* Load compat GDT. */
> + movq %rdi, %rax
> + addq $(compat_mode_gdt - kexec_reloc), %rax
leaq (compat_mode_gdt - kexec_reloc)(%rdi), %rax
[...]
> diff --git a/xen/common/kexec.c b/xen/common/kexec.c
[...]
> -static int kexec_load_unload_compat(unsigned long op,
> - XEN_GUEST_HANDLE_PARAM(void) uarg)
> +static int kexec_load_v1_compat(XEN_GUEST_HANDLE_PARAM(void) uarg)
> {
> #ifdef CONFIG_COMPAT
> compat_kexec_load_v1_t compat_load;
> @@ -808,49 +1011,113 @@ static int kexec_load_unload_compat(unsigned long op,
> load.type = compat_load.type;
> XLAT_kexec_image(&load.image, &compat_load.image);
>
> - return kexec_load_unload_internal(op, &load);
> -#else /* CONFIG_COMPAT */
> + return kexec_do_load_v1(&load, 1);
> +#else
Why did you removed comment?
> return 0;
Why not -ENOSYS?
> -#endif /* CONFIG_COMPAT */
> +#endif
Why did you removed comment?
[...]
> +static int kexec_unload_v1_compat(XEN_GUEST_HANDLE_PARAM(void) uarg)
> +{
> +#ifdef CONFIG_COMPAT
> + compat_kexec_load_v1_t compat_load;
> + xen_kexec_unload_t unload;
> +
> + if ( copy_from_guest(&compat_load, uarg, 1) )
> + return -EFAULT;
> +
> + unload.type = compat_load.type;
> + return kexec_do_unload(&unload);
> +#else
> + return 0;
Why not -ENOSYS?
> +#endif
> +}
Please check other similar places too.
Daniel
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