[Crash-utility] [PATCH v3] x86_64: VC exception stack support
HAGIO KAZUHITO(萩尾 一仁)
k-hagio-ab at nec.com
Wed Dec 16 01:23:56 UTC 2020
Hi Alexey,
-----Original Message-----
> Linux-5.10 has introduced SEV-ES support. New (5th) exception
> stack was added: 'VC_stack'.
>
> 'struct exception_stacks' cannot be used to obtain the size
> of VC stack, as the size of VC stack is zero there. Try
> another structure 'struct cea_exception_stacks' first as it
> represents actual CPU entry area with valid stack sizes and
> guard pages.
>
> Handled the case if VC stack is not mapped (present).
> It happens when SEV-ES is not active or not supported.
>
> Signed-off-by: Alexey Makhalov <amakhalov at vmware.com>
sorry for the delay, I had been busy with an exceptional task..
This patch looks good to me and tested ok with some vmcores whose
VC stack is not mapped that I have. Thank you for the update.
Acked-by: Kazuhito Hagio <k-hagio-ab at nec.com>
Kazu
> ---
> defs.h | 1 +
> x86_64.c | 48 ++++++++++++++++++++++++++++++++++++------------
> 2 files changed, 37 insertions(+), 12 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index 9594950..4aeeef5 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -5913,6 +5913,7 @@ struct x86_64_pt_regs_offsets {
> struct x86_64_stkinfo {
> ulong ebase[NR_CPUS][MAX_EXCEPTION_STACKS];
> int esize[MAX_EXCEPTION_STACKS];
> + char available[NR_CPUS][MAX_EXCEPTION_STACKS];
> ulong ibase[NR_CPUS];
> int isize;
> int NMI_stack_index;
> diff --git a/x86_64.c b/x86_64.c
> index 939c8a9..23a40a0 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -1369,6 +1369,7 @@ x86_64_ist_init(void)
> ulong init_tss;
> struct machine_specific *ms;
> struct syment *boot_sp, *tss_sp, *ist_sp;
> + char *exc_stack_struct_name = NULL;
>
> ms = machdep->machspec;
> if (!(tss_sp = per_cpu_symbol_search("per_cpu__init_tss"))) {
> @@ -1444,25 +1445,40 @@ x86_64_ist_init(void)
> return;
> }
>
> - if (MEMBER_EXISTS("exception_stacks", "NMI_stack")) {
> + if (MEMBER_EXISTS("cea_exception_stacks", "NMI_stack")) {
> + /* The effective cpu entry area mapping with guard pages. */
> + exc_stack_struct_name = "cea_exception_stacks";
> + } else if (MEMBER_EXISTS("exception_stacks", "NMI_stack")) {
> + /* The exception stacks' physical storage. No guard pages and no VC stack. */
> + exc_stack_struct_name = "exception_stacks";
> + }
> + if (exc_stack_struct_name) {
> for (i = 0; i < MAX_EXCEPTION_STACKS; i++) {
> if (STREQ(ms->stkinfo.exception_stacks[i], "DEBUG"))
> - ms->stkinfo.esize[i] = MEMBER_SIZE("exception_stacks", "DB_stack");
> + ms->stkinfo.esize[i] = MEMBER_SIZE(exc_stack_struct_name, "DB_stack");
> else if (STREQ(ms->stkinfo.exception_stacks[i], "NMI"))
> - ms->stkinfo.esize[i] = MEMBER_SIZE("exception_stacks", "NMI_stack");
> + ms->stkinfo.esize[i] = MEMBER_SIZE(exc_stack_struct_name, "NMI_stack");
> else if (STREQ(ms->stkinfo.exception_stacks[i], "DOUBLEFAULT"))
> - ms->stkinfo.esize[i] = MEMBER_SIZE("exception_stacks", "DF_stack");
> + ms->stkinfo.esize[i] = MEMBER_SIZE(exc_stack_struct_name, "DF_stack");
> else if (STREQ(ms->stkinfo.exception_stacks[i], "MCE"))
> - ms->stkinfo.esize[i] = MEMBER_SIZE("exception_stacks", "MCE_stack");
> + ms->stkinfo.esize[i] = MEMBER_SIZE(exc_stack_struct_name, "MCE_stack");
> + else if (STREQ(ms->stkinfo.exception_stacks[i], "VC"))
> + ms->stkinfo.esize[i] = MEMBER_SIZE(exc_stack_struct_name, "VC_stack");
> }
> /*
> - * Adjust the top-of-stack addresses down to the base stack address.
> + * Adjust the top-of-stack addresses down to the base stack address
> + * and set stack page availabilituy flag.
> */
> for (c = 0; c < kt->cpus; c++) {
> for (i = 0; i < MAX_EXCEPTION_STACKS; i++) {
> - if (ms->stkinfo.ebase[c][i] == 0)
> - continue;
> - ms->stkinfo.ebase[c][i] -= ms->stkinfo.esize[i];
> + if (ms->stkinfo.ebase[c][i])
> + ms->stkinfo.ebase[c][i] -= ms->stkinfo.esize[i];
> +
> + ms->stkinfo.available[c][i] = TRUE;
> + /* VC stack can be unmapped if SEV-ES is disabled or not supported. */
> + if (STREQ(ms->stkinfo.exception_stacks[i], "VC") &&
> + !accessible(ms->stkinfo.ebase[c][i]))
> + ms->stkinfo.available[c][i] = FALSE;
> }
> }
>
> @@ -1487,6 +1503,7 @@ x86_64_ist_init(void)
> else
> ms->stkinfo.esize[i] = esize;
> ms->stkinfo.ebase[c][i] -= ms->stkinfo.esize[i];
> + ms->stkinfo.available[c][i] = TRUE;
> }
> }
>
> @@ -2842,7 +2859,8 @@ x86_64_eframe_search(struct bt_info *bt)
> !(NUM_IN_BITMAP(bt->cpumask, c)))
> continue;
> for (i = 0; i < MAX_EXCEPTION_STACKS; i++) {
> - if (ms->stkinfo.ebase[c][i] == 0)
> + if (ms->stkinfo.ebase[c][i] == 0 ||
> + !ms->stkinfo.available[c][i])
> break;
> bt->hp->esp = ms->stkinfo.ebase[c][i];
> fprintf(fp, "CPU %d %s EXCEPTION STACK:",
> @@ -3288,7 +3306,8 @@ x86_64_in_exception_stack(struct bt_info *bt, int *estack_index)
>
> for (c = 0; !estack && (c < kt->cpus); c++) {
> for (i = 0; i < MAX_EXCEPTION_STACKS; i++) {
> - if (ms->stkinfo.ebase[c][i] == 0)
> + if (ms->stkinfo.ebase[c][i] == 0 ||
> + !ms->stkinfo.available[c][i])
> break;
> if ((rsp >= ms->stkinfo.ebase[c][i]) &&
> (rsp < (ms->stkinfo.ebase[c][i] +
> @@ -5097,7 +5116,7 @@ skip_stage:
> ms->stkinfo.esize[estack];
> console("x86_64_get_dumpfile_stack_frame: searching %s estack at %lx\n",
> ms->stkinfo.exception_stacks[estack], bt->stackbase);
> - if (!(bt->stackbase))
> + if (!(bt->stackbase && ms->stkinfo.available[bt->tc->processor][estack]))
> goto skip_stage;
> bt->stackbuf = ms->irqstack;
> alter_stackbuf(bt);
> @@ -5380,6 +5399,8 @@ x86_64_exception_stacks_init(void)
> ms->stkinfo.exception_stacks[ist-1] = "DOUBLEFAULT";
> if (strstr(buf, "machine"))
> ms->stkinfo.exception_stacks[ist-1] = "MCE";
> + if (strstr(buf, "vmm"))
> + ms->stkinfo.exception_stacks[ist-1] = "VC";
> }
> }
>
> @@ -5737,6 +5758,9 @@ x86_64_display_machine_stats(void)
> fprintf(fp, "%22s: %016lx",
> buf, machdep->machspec->stkinfo.ebase[c][i]);
>
> + if (!machdep->machspec->stkinfo.available[c][i])
> + fprintf(fp, " [unavailable]");
> +
> if (hide_offline_cpu(c))
> fprintf(fp, " [OFFLINE]\n");
> else
> --
> 2.11.0
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