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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/3] kexec: extend hypercall with improved load/unload ops
On Wed, Jan 16, 2013 at 04:29:04PM +0000, 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_v2 and KEXEC_CMD_kexec_unload_v2
> 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 load_v2 op looks similar to the Linux kexec_load system call and
> allows the guest to provide the image data to be loaded into the crash
> kernel memory region. The guest may also specify whether the image is
> 64-bit or 32-bit.
>
> The toolstack can now load images without kernel involvement. This is
> required for supporting kexec of crash kernels from PV-ops kernels.
>
> Note: This also changes the behaviour of the kexec op when a image is
> loaded with the old ABI. The code page will no longer be used which
> may result is incorrect behaviour in non-Linux guests. This allowed
> the code to be simpler and support for the old ABI is being removed in
> a subsequent patch anyway.
>
> [ This is a prototype and has the following limitations:
>
> - no compat implementation for kexec_load_v2.
> - 64-bit images are not supported.
> - 32-bit images are called with paging enabled (Linux starts 32-bit
> images with paging disabled). ]
>
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
> xen/arch/x86/machine_kexec.c | 73 ++------------
> xen/arch/x86/x86_64/compat_kexec.S | 25 -----
> xen/common/kexec.c | 204
> ++++++++++++++++++++++++++++++++++--
> xen/include/public/kexec.h | 44 ++++++++
> xen/include/xen/kexec.h | 18 ++--
> 5 files changed, 255 insertions(+), 109 deletions(-)
>
> diff --git a/xen/arch/x86/machine_kexec.c b/xen/arch/x86/machine_kexec.c
> index 8191ef1..7131d20 100644
> --- a/xen/arch/x86/machine_kexec.c
> +++ b/xen/arch/x86/machine_kexec.c
> @@ -12,62 +12,16 @@
> #include <asm/fixmap.h>
> #include <asm/hpet.h>
>
> -typedef void (*relocate_new_kernel_t)(
> - unsigned long indirection_page,
> - unsigned long *page_list,
> - unsigned long start_address,
> - unsigned int preserve_context);
> -
> -int machine_kexec_load(int type, int slot, xen_kexec_image_t *image)
> +int machine_kexec_load(struct kexec_image *image)
> {
> - unsigned long prev_ma = 0;
> - int fix_base = FIX_KEXEC_BASE_0 + (slot * (KEXEC_XEN_NO_PAGES >> 1));
> - int k;
> -
> - /* setup fixmap to point to our pages and record the virtual address
> - * in every odd index in page_list[].
> - */
> -
> - for ( k = 0; k < KEXEC_XEN_NO_PAGES; k++ )
> - {
> - if ( (k & 1) == 0 )
> - {
> - /* Even pages: machine address. */
> - prev_ma = image->page_list[k];
> - }
> - else
> - {
> - /* Odd pages: va for previous ma. */
> - if ( is_pv_32on64_domain(dom0) )
> - {
> - /*
> - * The compatability bounce code sets up a page table
> - * with a 1-1 mapping of the first 1G of memory so
> - * VA==PA here.
> - *
> - * This Linux purgatory code still sets up separate
> - * high and low mappings on the control page (entries
> - * 0 and 1) but it is harmless if they are equal since
> - * that PT is not live at the time.
> - */
> - image->page_list[k] = prev_ma;
> - }
> - else
> - {
> - set_fixmap(fix_base + (k >> 1), prev_ma);
> - image->page_list[k] = fix_to_virt(fix_base + (k >> 1));
> - }
> - }
> - }
> -
> return 0;
> }
>
> -void machine_kexec_unload(int type, int slot, xen_kexec_image_t *image)
> +void machine_kexec_unload(struct kexec_image *image)
> {
> }
>
> -void machine_reboot_kexec(xen_kexec_image_t *image)
> +void machine_reboot_kexec(struct kexec_image *image)
> {
> BUG_ON(smp_processor_id() != 0);
> smp_send_stop();
> @@ -75,7 +29,7 @@ void machine_reboot_kexec(xen_kexec_image_t *image)
> BUG();
> }
>
> -void machine_kexec(xen_kexec_image_t *image)
> +void machine_kexec(struct kexec_image *image)
> {
> struct desc_ptr gdt_desc = {
> .base = (unsigned long)(boot_cpu_gdt_table -
> FIRST_RESERVED_GDT_ENTRY),
> @@ -116,22 +70,11 @@ void machine_kexec(xen_kexec_image_t *image)
> */
> asm volatile ( "lgdt %0" : : "m" (gdt_desc) );
>
> - if ( is_pv_32on64_domain(dom0) )
> - {
> - compat_machine_kexec(image->page_list[1],
> - image->indirection_page,
> - image->page_list,
> - image->start_address);
> - }
> + if ( image->class == KEXEC_CLASS_32 )
> + compat_machine_kexec(image->entry_maddr);
Why do you need that?
> else
> - {
> - relocate_new_kernel_t rnk;
> -
> - rnk = (relocate_new_kernel_t) image->page_list[1];
> - (*rnk)(image->indirection_page, image->page_list,
> - image->start_address,
> - 0 /* preserve_context */);
> - }
> + /* FIXME */
> + panic("KEXEC_CLASS_64 not yet supported\n");
> }
>
> int machine_kexec_get(xen_kexec_range_t *range)
> diff --git a/xen/arch/x86/x86_64/compat_kexec.S
> b/xen/arch/x86/x86_64/compat_kexec.S
> index fc92af9..d853231 100644
> --- a/xen/arch/x86/x86_64/compat_kexec.S
> +++ b/xen/arch/x86/x86_64/compat_kexec.S
> @@ -36,21 +36,6 @@
> ENTRY(compat_machine_kexec)
> /* x86/64 x86/32 */
> /* %rdi - relocate_new_kernel_t CALL */
> - /* %rsi - indirection page 4(%esp) */
> - /* %rdx - page_list 8(%esp) */
> - /* %rcx - start address 12(%esp) */
> - /* cpu has pae 16(%esp) */
> -
> - /* Shim the 64 bit page_list into a 32 bit page_list. */
> - mov $12,%r9
> - lea compat_page_list(%rip), %rbx
> -1: dec %r9
> - movl (%rdx,%r9,8),%eax
> - movl %eax,(%rbx,%r9,4)
> - test %r9,%r9
> - jnz 1b
> -
> - RELOCATE_SYM(compat_page_list,%rdx)
>
> /* Relocate compatibility mode entry point address. */
> RELOCATE_MEM(compatibility_mode_far,%eax)
> @@ -118,12 +103,6 @@ compatibility_mode:
> movl %eax, %gs
> movl %eax, %ss
>
> - /* Push arguments onto stack. */
> - pushl $0 /* 20(%esp) - preserve context */
> - pushl $1 /* 16(%esp) - cpu has pae */
> - pushl %ecx /* 12(%esp) - start address */
> - pushl %edx /* 8(%esp) - page list */
> - pushl %esi /* 4(%esp) - indirection page */
> pushl %edi /* 0(%esp) - CALL */
>
> /* Disable paging and therefore leave 64 bit mode. */
> @@ -153,10 +132,6 @@ compatibility_mode:
> ud2
>
> .data
> - .align 4
> -compat_page_list:
> - .fill 12,4,0
> -
> .align 32,0
>
> /*
> diff --git a/xen/common/kexec.c b/xen/common/kexec.c
> index 25ebd6a..56bf8b4 100644
> --- a/xen/common/kexec.c
> +++ b/xen/common/kexec.c
> @@ -45,7 +45,7 @@ static Elf_Note *xen_crash_note;
>
> static cpumask_t crash_saved_cpus;
>
> -static xen_kexec_image_t kexec_image[KEXEC_IMAGE_NR];
> +static struct kexec_image kexec_image[KEXEC_IMAGE_NR];
>
> #define KEXEC_FLAG_DEFAULT_POS (KEXEC_IMAGE_NR + 0)
> #define KEXEC_FLAG_CRASH_POS (KEXEC_IMAGE_NR + 1)
> @@ -316,7 +316,7 @@ void kexec_crash(void)
>
> static long kexec_reboot(void *_image)
> {
> - xen_kexec_image_t *image = _image;
> + struct kexec_image *image = _image;
>
> kexecing = TRUE;
>
> @@ -732,9 +732,19 @@ static void crash_save_vmcoreinfo(void)
> #endif
> }
>
> +static void kexec_unload_slot(int slot)
> +{
> + struct kexec_image *image = &kexec_image[slot];
> +
> + if ( test_and_clear_bit(slot, &kexec_flags) )
> + {
> + machine_kexec_unload(image);
> + }
> +}
> +
> static int kexec_load_unload_internal(unsigned long op, xen_kexec_load_t
> *load)
> {
> - xen_kexec_image_t *image;
> + struct kexec_image *image;
> int base, bit, pos;
> int ret = 0;
>
> @@ -750,9 +760,13 @@ static int kexec_load_unload_internal(unsigned long op,
> xen_kexec_load_t *load)
>
> BUG_ON(test_bit((base + !pos), &kexec_flags)); /* must be free */
>
> - memcpy(image, &load->image, sizeof(*image));
> + if ( is_pv_32on64_domain(dom0) )
> + image->class = KEXEC_CLASS_32;
> + else
> + image->class = KEXEC_CLASS_64;
Ditto.
> + image->entry_maddr = load->image.start_address;
>
> - if ( !(ret = machine_kexec_load(load->type, base + !pos, image)) )
> + if ( !(ret = machine_kexec_load(image)) )
> {
> /* Set image present bit */
> set_bit((base + !pos), &kexec_flags);
> @@ -767,11 +781,7 @@ static int kexec_load_unload_internal(unsigned long op,
> xen_kexec_load_t *load)
> /* Unload the old image if present and load successful */
> if ( ret == 0 && !test_bit(KEXEC_FLAG_IN_PROGRESS, &kexec_flags) )
> {
> - if ( test_and_clear_bit((base + pos), &kexec_flags) )
> - {
> - image = &kexec_image[base + pos];
> - machine_kexec_unload(load->type, base + pos, image);
> - }
> + kexec_unload_slot(base + pos);
> }
>
> return ret;
> @@ -816,7 +826,7 @@ static int kexec_load_unload_compat(unsigned long op,
> static int kexec_exec(XEN_GUEST_HANDLE_PARAM(void) uarg)
> {
> xen_kexec_exec_t exec;
> - xen_kexec_image_t *image;
> + struct kexec_image *image;
> int base, bit, pos, ret = -EINVAL;
>
> if ( unlikely(copy_from_guest(&exec, uarg, 1)) )
> @@ -845,6 +855,162 @@ static int kexec_exec(XEN_GUEST_HANDLE_PARAM(void) uarg)
> return -EINVAL; /* never reached */
> }
>
> +static int kexec_load_segments(xen_kexec_load_v2_t *load)
> +{
> + unsigned s;
> + bool_t valid_entry = 0;
> +
> + for ( s = 0; s < load->nr_segments; s++ )
> + {
> + xen_kexec_segment_t seg;
> + unsigned long to_copy;
> + unsigned long src_offset;
> + unsigned long dest;
> +
> + if ( copy_from_guest_offset(&seg, load->segments, s, 1) )
> + return -EFAULT;
> +
> + /* Caller is responsible for ensuring the crash space is
> + shared between multiple users of the load call. Xen just
> + validates the load is to somewhere within the region. */
> +
> + if ( seg.dest_maddr < kexec_crash_area.start
> + || seg.dest_maddr + seg.size > kexec_crash_area.start +
> kexec_crash_area.size)
> + return -EINVAL;
This way you are breaking regular kexec support which
does not use prealocated area. As I said earlier you
should use kexec code from Linux Kernel (with relevant
changes). It has all needed stuff and you do not need
to reinvent the wheel.
> +
> + if ( load->entry_maddr >= seg.dest_maddr
> + && load->entry_maddr < seg.dest_maddr + seg.size)
> + valid_entry = 1;
> +
> + to_copy = seg.size;
> + src_offset = 0;
> + dest = seg.dest_maddr;
> +
> + while ( to_copy )
> + {
> + unsigned long dest_mfn;
> + size_t dest_off;
> + void *dest_va;
> + size_t size;
> +
> + dest_mfn = dest >> PAGE_SHIFT;
> + dest_off = dest & ~PAGE_MASK;
> +
> + size = min(PAGE_SIZE - dest_off, to_copy);
> +
> + dest_va = vmap(&dest_mfn, 1);
> + if ( dest_va == NULL )
> + return -EINVAL;
> +
> + copy_from_guest_offset(dest_va, seg.buf, src_offset, size);
> +
> + vunmap(dest_va);
> +
> + to_copy -= size;
> + src_offset += size;
> + dest += size;
> + }
> + }
> +
> + /* Entry point is somewhere in a loaded segment? */
> + if ( !valid_entry )
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +static int slot_to_pos_bit(int slot)
> +{
> + return KEXEC_IMAGE_NR + slot / 2;
> +}
> +
> +static int kexec_load_slot(int slot, xen_kexec_load_v2_t *load)
> +{
> + struct kexec_image *image = &kexec_image[slot];
> + int ret;
> +
> + BUG_ON(test_bit(slot, &kexec_flags)); /* must be free */
> +
> + /* validate and load each segment. */
> + ret = kexec_load_segments(load);
> + if ( ret < 0 )
> + return ret;
> +
> + image->entry_maddr = load->entry_maddr;
> +
> + ret = machine_kexec_load(image);
> + if ( ret < 0 )
> + return ret;
> +
> + /* Set image present bit */
> + set_bit(slot, &kexec_flags);
> +
> + /* Make new image the active one */
> + change_bit(slot_to_pos_bit(slot), &kexec_flags);
> +
> + crash_save_vmcoreinfo();
> +
> + return ret;
> +}
> +
> +
> +static int kexec_load_v2(XEN_GUEST_HANDLE_PARAM(void) uarg)
> +{
> + xen_kexec_load_v2_t load;
> + int base, bit, pos, slot;
> + struct kexec_image *image;
> + int ret;
> +
> + if ( unlikely(copy_from_guest(&load, uarg, 1)) )
> + return -EFAULT;
> +
> + if ( kexec_load_get_bits(load.type, &base, &bit) )
> + return -EINVAL;
> +
> + pos = (test_bit(bit, &kexec_flags) != 0);
> + slot = base + !pos;
> + image = &kexec_image[slot];
> +
> + switch ( load.class )
> + {
> + case KEXEC_CLASS_32:
> + case KEXEC_CLASS_64:
> + image->class = load.class;
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + ret = kexec_load_slot(slot, &load);
> +
> + /* Unload the old image if present and load successful */
> + if ( ret == 0 && !test_bit(KEXEC_FLAG_IN_PROGRESS, &kexec_flags) )
> + {
> + kexec_unload_slot(slot ^ 0x1);
> + }
> +
> + return ret;
> +}
> +
> +static int kexec_unload_v2(XEN_GUEST_HANDLE_PARAM(void) uarg)
> +{
> + xen_kexec_unload_v2_t unload;
> + int base, bit, pos, slot;
> +
> + if ( unlikely(copy_from_guest(&unload, uarg, 1)) )
> + return -EFAULT;
> +
> + if ( kexec_load_get_bits(unload.type, &base, &bit) )
> + return -EINVAL;
> +
> + pos = (test_bit(bit, &kexec_flags) != 0);
> + slot = base + !pos;
> +
> + kexec_unload_slot(slot);
> +
> + return 0;
> +}
> +
> static int do_kexec_op_internal(unsigned long op,
> XEN_GUEST_HANDLE_PARAM(void) uarg,
> bool_t compat)
> @@ -882,6 +1048,22 @@ static int do_kexec_op_internal(unsigned long op,
> case KEXEC_CMD_kexec:
> ret = kexec_exec(uarg);
> break;
> + case KEXEC_CMD_kexec_load_v2:
> + spin_lock_irqsave(&kexec_lock, flags);
> + if ( !test_bit(KEXEC_FLAG_IN_PROGRESS, &kexec_flags) )
> + ret = kexec_load_v2(uarg);
> + else
> + ret = -EBUSY;
> + spin_unlock_irqrestore(&kexec_lock, flags);
> + break;
> + case KEXEC_CMD_kexec_unload_v2:
> + spin_lock_irqsave(&kexec_lock, flags);
> + if ( !test_bit(KEXEC_FLAG_IN_PROGRESS, &kexec_flags) )
> + ret = kexec_unload_v2(uarg);
> + else
> + ret = -EBUSY;
> + spin_unlock_irqrestore(&kexec_lock, flags);
> + break;
> }
>
> return ret;
> diff --git a/xen/include/public/kexec.h b/xen/include/public/kexec.h
> index 61a8d7d..4b7d637 100644
> --- a/xen/include/public/kexec.h
> +++ b/xen/include/public/kexec.h
> @@ -83,6 +83,8 @@
> #define KEXEC_TYPE_DEFAULT 0
> #define KEXEC_TYPE_CRASH 1
>
> +#define KEXEC_CLASS_32 1 /* 32-bit image. */
> +#define KEXEC_CLASS_64 2 /* 64-bit image. */
???
>
> /* The kexec implementation for Xen allows the user to load two
> * types of kernels, KEXEC_TYPE_DEFAULT and KEXEC_TYPE_CRASH.
> @@ -152,6 +154,48 @@ typedef struct xen_kexec_range {
> unsigned long start;
> } xen_kexec_range_t;
>
> +/*
> + * A contiguous chunk of a kexec image and it's destination machine
> + * address.
> + */
> +typedef struct xen_kexec_segment {
> + XEN_GUEST_HANDLE(const_void) buf;
> + uint32_t size;
> + uint64_t dest_maddr;
> +} xen_kexec_segment_t;
> +DEFINE_XEN_GUEST_HANDLE(xen_kexec_segment_t);
> +
> +/*
> + * Load a kexec image into memory.
> + *
> + * Each segment of the image must reside in the memory region reserved
> + * for kexec (KEXEC_RANGE_MA_CRASH) and the entry point must be within
> + * the image.
> + *
> + * The caller is responsible for ensuring that multiple images do not
> + * overlap.
> + */
> +#define KEXEC_CMD_kexec_load_v2 4
> +typedef struct xen_kexec_load_v2 {
> + uint8_t type; /* One of KEXEC_TYPE_* */
> + uint8_t class; /* One of KEXEC_CLASS_* */
Why do not use one member called flags (uint32_t or uint64_t)?
This way you could add quite easily new flags in the future.
Daniel
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