Re: [Crash-utility] [PATCH v2] x86_64: VC exception stack support

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.

Signed-off-by: Alexey Makhalov <amakhalov(a)vmware.com&gt; --- 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))

+ 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