Hi Alexey,
Thanks for updating this patch.
-----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 size of
> VC stack, as it equals zero there. Try another structure
> 'struct cea_exception_stacks' first as it represents actual
> CPU entry area with valid stack sizes and guard pages.
>
> Added check for the case when VC stack is not mapped.
> It happens when SEV-ES is not active or not supported.
Seems one more check for "bt -E" is needed.
crash> bt -E
...
CPU 0 VC EXCEPTION STACK:
bt: invalid kernel virtual address: fffffe0000011000 type: "stack contents"
bt: read of stack at fffffe0000011000 failed
>
> Signed-off-by: Alexey Makhalov <amakhalov@xxxxxxxxxx>
> ---
> x86_64.c | 29 ++++++++++++++++++++++++-----
> 1 file changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/x86_64.c b/x86_64.c
> index fc05e8a..6160305 100644
> --- a/x86_64.c
> +++ b/x86_64.c
> @@ -1367,6 +1367,7 @@ 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"))) {
> @@ -1442,16 +1443,25 @@ 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.
> @@ -5092,6 +5102,13 @@ skip_stage:
> ms->stkinfo.exception_stacks[estack], bt->stackbase);
> if (!(bt->stackbase))
> goto skip_stage;
> + /* VC stack can be unmapped if SEV-ES is inactive. */
> + if (STREQ(ms->stkinfo.exception_stacks[estack], "VC")) {
> + physaddr_t phys;
> + /* Skip this stack if page is not present. */
> + if (!kvtop(NULL, bt->stackbase, &phys, 0))
Nitpicking, kvtop() accepts NULL for paddr. (or there is also accessible())
Thanks,
Kazu
> + goto skip_stage;
> + }
> bt->stackbuf = ms->irqstack;
> alter_stackbuf(bt);
> in_nmi_stack = STREQ(ms->stkinfo.exception_stacks[estack], "NMI");
> @@ -5373,6 +5390,8 @@ 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";
> }
> }
>
> --
> 2.11.0
--
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