[Crash-utility] some updates of xencrash
Dave Anderson
anderson at redhat.com
Mon Apr 21 13:09:59 UTC 2008
Itsuro ODA wrote:
> Hi Dave,
>
> I thought it is better to be small value from the view point
> to save 'xen_phys_start' value in the crashinfo.
>
> From the view point of users you are right. It should be
> '--xen_phys_start=<address>'.
Hi Itsuro,
But even from the kernel viewpoint, I'm not sure why it would be better?
The xen_phys_start symbol is an unsigned long, and its container in the
crash_xen_info_t is an unsigned long. So I don't see any benefit or reason
to make it smaller.
>
>> Another theoretical question -- since the /proc/iomem exports the
>> xen_phys_start variable to user space, is there any way it could
>> be handled entirely in user space by kexec-tools?
>
> Theoretically yes. But it is necessary to add another ElfNote section.
> I thought it is the smallest modication necessary to add 'xen_phys_start'
> in the crashinfo.
> Do you think which is better ?
That's a good question. My concern would be to have an easier way for customers
to deal with the problem without having to upgrade the kernel package; it's always
easier to upgrade a user-package.
However, whatever gets fixed goes beyond the scope of the crash utility.
For now, the crash utility will need the --xen-phys_start=xxxx workaround
because the RHEL5.2 kernel will be released without a fix. And that
decision will have to made by the kernel kexec/kdump and kexec-tools
maintainers. Can you bring up this discussion on the kexec list?
Thanks,
Dave
>
> Thanks.
> Itsuro Oda
>
> On Fri, 18 Apr 2008 10:14:04 -0400
> Dave Anderson <anderson at redhat.com> wrote:
>
>> Itsuro ODA wrote:
>>> Hi,
>>>
>>> The attached is some fixes which are necessary for xencrash to use
>>> for the newer version of xen (after 3.1.0, ex. 3.1.2, 3.2.0).
>>>
>>> * x86
>>> - add some symbols which are used to know the boundary
>>> condition at the tracing in 'bt'.
>>> - fix for the symbol 'idle_pg_table_l3' going away.
>>>
>>> * x86_64
>>> - fix for the virtual address area of xen code/data is added.
>>> - fix for the symbol 'idle_pg_table_l4' going away.
>>> - add the option '--xen_phys_start_mfn='
>>> newer version of xen (ex. RHEL5.2, 3.2.0) moves the
>>> physical(machine) address of xen code/data area after
>>> the system started up.
>>> The relocated physical(machine) address of xen code/data
>>> area is necessary to use xencrash.
>>> The value can be got by 'cat /proc/iomem' under dom0.
>>> -------------------------------------------------------
>>> # cat /proc/iomem
>>> ...
>>> 7e600000-7f5fffff : Hypervisor code and data *** this line
>>> ...
>>> -------------------------------------------------------
>>> ex. to use xencrash:
>>> # crash --xen_phys_start_mfn=0x7e600 xen-syms vmcore
>>> - extract 'xen_phys_start_mfn' from the XEN_ELFNOTE_CRASH_INFO
>>> ElfNote.
>>> This is experimental code because it is necessary to modify
>>> the xen to add the xen_phys_start_mfn value in the ElfNote
>>> at crash time. (the patch is also attached in this mail.)
>>> A sample dump is availavle in the following URL:
>>> http://people.valinux.co.jp/~oda/x86_64_dump_080417.tar.gz
>>>
>>> This patch is for crash-4.0-6.2.
>>>
>>> Thanks.
>>> Itsuro Oda
>> Hi Itsuro,
>>
>> Thanks very much for the quick response.
>>
>> I have one relatively minor issue. I understand that the previously existing
>> "--p2m_mfn" option was expressed as an mfn, and that made sense because its value
>> exists in the xen hypervisor code as an mfn value (actually a xen_pfn_t).
>>
>> But it seems unnecessary to bother going through the translation of the
>> hypservisors's "xen_phys_start" physical address into an mfn? And then
>> only to have the crash utility have to turn it back into a physical address
>> when it uses it? Why not just leave it as a physical address in both the
>> kernel patch, and when passing it to the crash utility?
>>
>> From a user's standpoint, when it's necessary to pre-determine the argument from
>> a hypervisor/dom0 vmcore that doesn't contain it, the xen_phys_start can be determined
>> by either reading /proc/iomem on the live system, where as you've shown in
>> the example above, it's 7e600000:
>>
>> > # cat /proc/iomem
>> > ...
>> > 7e600000-7f5fffff : Hypervisor code and data *** this line
>> > ...
>>
>> Alternatively, the same dom0/HV kdump vmcore can be run in a crash session using
>> the dom0 vmlinux, where in this example vmcore, it's 0x3f000000:
>>
>> crash> px xen_hypervisor_res
>> xen_hypervisor_res = $3 = {
>> start = 0x3f000000,
>> end = 0x3fffffff,
>> name = 0xffffffff8049ab72 "Hypervisor code and data",
>> flags = 0x80000200,
>> parent = 0xffff880000001180,
>> sibling = 0x0,
>> child = 0xffff8800000000a8
>> }
>>
>> For convenience sake, I'd prefer to just leave it as that, without
>> needlessly forcing the user to translate the above into an mfn, so
>> that they can simply enter: "crash --xen_phys_start=0x3f000000 ..."
>>
>> The same thing applies to the kernel patch -- just leave it in its
>> natural state as a physical (machine) address.
>>
>> Unfortunately it's already going to be an annoyance to have to pre-determine
>> the xen_phys_start value -- so why bother making it even more cryptic by
>> forcing the user to turn it into an mfn?
>>
>> Another theoretical question -- since the /proc/iomem exports the
>> xen_phys_start variable to user space, is there any way it could
>> be handled entirely in user space by kexec-tools?
>>
>> Dave
>>
>>
>>> === for x86 ===
>>> --- lkcd_x86_trace.c.org 2008-04-17 10:13:05.000000000 +0900
>>> +++ lkcd_x86_trace.c 2008-04-17 10:13:17.000000000 +0900
>>> @@ -1423,6 +1423,7 @@
>>> if (XEN_HYPER_MODE()) {
>>> func_name = kl_funcname(pc);
>>> if (STREQ(func_name, "idle_loop") || STREQ(func_name, "hypercall")
>>> + || STREQ(func_name, "tracing_off")
>>> || STREQ(func_name, "handle_exception")) {
>>> UPDATE_FRAME(func_name, pc, 0, sp, bp, asp, 0, 0, bp - sp, 0);
>>> return(trace->nframes);
>>> @@ -1682,6 +1683,7 @@
>>> if (func_name && XEN_HYPER_MODE()) {
>>> if (STREQ(func_name, "continue_nmi") ||
>>> STREQ(func_name, "vmx_asm_vmexit_handler") ||
>>> + STREQ(func_name, "handle_nmi_mce") ||
>>> STREQ(func_name, "deferred_nmi")) {
>>> /* Interrupt frame */
>>> sp = curframe->fp + 4;
>>> --- x86.c.org 2008-04-17 10:29:21.000000000 +0900
>>> +++ x86.c 2008-04-17 10:31:51.000000000 +0900
>>> @@ -2846,7 +2846,10 @@
>>> *paddr = kvaddr - DIRECTMAP_VIRT_START;
>>> return TRUE;
>>> }
>>> - pgd = (ulonglong *)symbol_value("idle_pg_table_l3");
>>> + if (symbol_exists("idle_pg_table_l3"))
>>> + pgd = (ulonglong *)symbol_value("idle_pg_table_l3");
>>> + else
>>> + pgd = (ulonglong *)symbol_value("idle_pg_table");
>>> } else {
>>> if (!vt->vmalloc_start) {
>>> *paddr = VTOP(kvaddr);
>>> @@ -4965,7 +4968,8 @@
>>> break;
>>>
>>> case PRE_GDB:
>>> - if (symbol_exists("idle_pg_table_l3")) {
>>> + if (symbol_exists("create_pae_xen_mappings") ||
>>> + symbol_exists("idle_pg_table_l3")) {
>>> machdep->flags |= PAE;
>>> PGDIR_SHIFT = PGDIR_SHIFT_3LEVEL;
>>> PTRS_PER_PTE = PTRS_PER_PTE_3LEVEL;
>>>
>>> === for x86_64 ===
>>> --- defs.h.org 2008-04-17 15:03:14.000000000 +0900
>>> +++ defs.h 2008-04-17 15:41:10.000000000 +0900
>>> @@ -2162,10 +2162,13 @@
>>>
>>> #define FILL_PML4_HYPER() { \
>>> if (!machdep->machspec->last_pml4_read) { \
>>> - readmem(symbol_value("idle_pg_table_4"), KVADDR, \
>>> - machdep->machspec->pml4, PAGESIZE(), "idle_pg_table_4", \
>>> + unsigned long idle_pg_table = \
>>> + symbol_exists("idle_pg_table_4") ? symbol_value("idle_pg_table_4") : \
>>> + symbol_value("idle_pg_table"); \
>>> + readmem(idle_pg_table, KVADDR, \
>>> + machdep->machspec->pml4, PAGESIZE(), "idle_pg_table", \
>>> FAULT_ON_ERROR); \
>>> - machdep->machspec->last_pml4_read = symbol_value("idle_pg_table_4"); \
>>> + machdep->machspec->last_pml4_read = idle_pg_table; \
>>> }\
>>> }
>>>
>>> @@ -4081,6 +4084,8 @@
>>> void get_kdump_regs(struct bt_info *, ulong *, ulong *);
>>> void xen_kdump_p2m_mfn(char *);
>>> int is_sadump_xen(void);
>>> +void set_xen_phys_start_mfn(char *);
>>> +ulong xen_phys_start_mfn(void);
>>>
>>> /*
>>> * diskdump.c
>>> --- main.c.org 2008-04-17 15:26:37.000000000 +0900
>>> +++ main.c 2008-04-17 15:45:18.000000000 +0900
>>> @@ -48,6 +48,7 @@
>>> {"no_ikconfig", 0, 0, 0},
>>> {"hyper", 0, 0, 0},
>>> {"p2m_mfn", required_argument, 0, 0},
>>> + {"xen_phys_start_mfn", required_argument, 0, 0},
>>> {"zero_excluded", 0, 0, 0},
>>> {"no_panic", 0, 0, 0},
>>> {"more", 0, 0, 0},
>>> @@ -155,6 +156,9 @@
>>> else if (STREQ(long_options[option_index].name, "p2m_mfn"))
>>> xen_kdump_p2m_mfn(optarg);
>>>
>>> + else if (STREQ(long_options[option_index].name, "xen_phys_start_mfn"))
>>> + set_xen_phys_start_mfn(optarg);
>>> +
>>> else if (STREQ(long_options[option_index].name, "zero_excluded"))
>>> *diskdump_flags |= ZERO_EXCLUDED;
>>>
>>> --- netdump.c.org 2008-04-17 15:09:06.000000000 +0900
>>> +++ netdump.c 2008-04-17 15:48:44.000000000 +0900
>>> @@ -1521,6 +1521,8 @@
>>> */
>>> if (!nd->xen_kdump_data->p2m_mfn)
>>> nd->xen_kdump_data->p2m_mfn = *(uptr+(words-1));
>>> + if (words > 9 && !nd->xen_kdump_data->xen_phys_start_mfn)
>>> + nd->xen_kdump_data->xen_phys_start_mfn = *(uptr+(words-2));
>>> }
>>> }
>>> break;
>>> @@ -1724,6 +1726,8 @@
>>> */
>>> if (!nd->xen_kdump_data->p2m_mfn)
>>> nd->xen_kdump_data->p2m_mfn = *(up+(words-1));
>>> + if (words > 9 && !nd->xen_kdump_data->xen_phys_start_mfn)
>>> + nd->xen_kdump_data->xen_phys_start_mfn = *(up+(words-2));
>>> }
>>> }
>>> break;
>>> @@ -2312,3 +2316,22 @@
>>>
>>> return FALSE;
>>> }
>>> +
>>> +void
>>> +set_xen_phys_start_mfn(char *arg)
>>> +{
>>> + ulong value;
>>> + int errflag = 0;
>>> +
>>> + value = htol(arg, RETURN_ON_ERROR|QUIET, &errflag);
>>> + if (!errflag)
>>> + xen_kdump_data.xen_phys_start_mfn = value;
>>> + else
>>> + error(WARNING, "invalid xen_phys_start_mfn argument: %s\n", arg);
>>> +}
>>> +
>>> +ulong
>>> +xen_phys_start_mfn(void)
>>> +{
>>> + return nd->xen_kdump_data->xen_phys_start_mfn;
>>> +}
>>> --- netdump.h.org 2008-04-17 15:38:59.000000000 +0900
>>> +++ netdump.h 2008-04-17 15:39:38.000000000 +0900
>>> @@ -109,6 +109,7 @@
>>> ulong accesses;
>>> int p2m_frames;
>>> ulong *p2m_mfn_frame_list;
>>> + ulong xen_phys_start_mfn;
>>> };
>>>
>>> #define KDUMP_P2M_INIT (0x1)
>>> --- x86_64.c.org 2008-04-17 15:34:32.000000000 +0900
>>> +++ x86_64.c 2008-04-17 15:36:53.000000000 +0900
>>> @@ -1401,6 +1401,10 @@
>>> return FALSE;
>>>
>>> if (XEN_HYPER_MODE()) {
>>> + if (XENTEXT_VIRT_ADDR(kvaddr)) {
>>> + *paddr = kvaddr - __XEN_VIRT_START + (xen_phys_start_mfn() << PAGESHIFT());
>>> + return TRUE;
>>> + }
>>> if (DIRECTMAP_VIRT_ADDR(kvaddr)) {
>>> *paddr = kvaddr - DIRECTMAP_VIRT_START;
>>> return TRUE;
>>> --- xen_hyper_defs.h.org 2008-04-17 15:31:23.000000000 +0900
>>> +++ xen_hyper_defs.h 2008-04-17 15:34:15.000000000 +0900
>>> @@ -64,6 +64,9 @@
>>> #define DIRECTMAP_VIRT_START (0xffff830000000000)
>>> #define DIRECTMAP_VIRT_END (0xffff840000000000)
>>> #define PAGE_OFFSET_XEN_HYPER DIRECTMAP_VIRT_START
>>> +#define __XEN_VIRT_START (0xFFFF828C80000000)
>>> +#define XENTEXT_VIRT_ADDR(vaddr) \
>>> + (((vaddr) >= __XEN_VIRT_START) && ((vaddr) < DIRECTMAP_VIRT_START))
>>> #endif
>>>
>>> #ifdef IA64
>>>
>>> === Xen (explanation purpose) ===
>>> --- include/xen/elfcore.h.org 2008-04-17 14:11:41.000000000 +0900
>>> +++ include/xen/elfcore.h 2008-04-17 14:11:57.000000000 +0900
>>> @@ -66,6 +66,7 @@
>>> unsigned long xen_compile_time;
>>> unsigned long tainted;
>>> #ifdef CONFIG_X86
>>> + unsigned long xen_phys_start_mfn;
>>> unsigned long dom0_pfn_to_mfn_frame_list_list;
>>> #endif
>>> } crash_xen_info_t;
>>> --- arch/x86/crash.c.org 2008-04-17 14:12:51.000000000 +0900
>>> +++ arch/x86/crash.c 2008-04-17 14:13:13.000000000 +0900
>>> @@ -102,6 +102,7 @@
>>> hvm_disable();
>>>
>>> info = kexec_crash_save_info();
>>> + info->xen_phys_start_mfn = xen_phys_start >> PAGE_SHIFT;
>>> info->dom0_pfn_to_mfn_frame_list_list =
>>> arch_get_pfn_to_mfn_frame_list_list(dom0);
>>> }
>
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