From: Joerg Roedel <jroedel@suse.de>
Date: Mon, 7 Sep 2020 15:15:43 +0200
Subject: x86/sev-es: Allocate and map an IST stack for #VC handler
Git-commit: 02772fb9b68e6a72a5e17f994048df832fe2b15e
Patch-mainline: v5.10-rc1
References: jsc#SLE-14337
Allocate and map an IST stack and an additional fall-back stack for
the #VC handler. The memory for the stacks is allocated only when
SEV-ES is active.
The #VC handler needs to use an IST stack because a #VC exception can be
raised from kernel space with unsafe stack, e.g. in the SYSCALL entry
path.
Since the #VC exception can be nested, the #VC handler switches back to
the interrupted stack when entered from kernel space. If switching back
is not possible, the fall-back stack is used.
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-43-joro@8bytes.org
---
arch/x86/include/asm/cpu_entry_area.h | 41 ++++++++++++++++++++--------------
arch/x86/include/asm/page_64_types.h | 1
arch/x86/kernel/cpu/common.c | 2 +
arch/x86/kernel/dumpstack_64.c | 8 ++++--
arch/x86/kernel/sev-es.c | 33 +++++++++++++++++++++++++++
5 files changed, 67 insertions(+), 18 deletions(-)
--- a/arch/x86/include/asm/cpu_entry_area.h
+++ b/arch/x86/include/asm/cpu_entry_area.h
@@ -10,29 +10,33 @@
#ifdef CONFIG_X86_64
/* Macro to enforce the same ordering and stack sizes */
-#define ESTACKS_MEMBERS(guardsize, db2_holesize)\
- char DF_stack_guard[guardsize]; \
- char DF_stack[EXCEPTION_STKSZ]; \
- char NMI_stack_guard[guardsize]; \
- char NMI_stack[EXCEPTION_STKSZ]; \
- char DB2_stack_guard[guardsize]; \
- char DB2_stack[db2_holesize]; \
- char DB1_stack_guard[guardsize]; \
- char DB1_stack[EXCEPTION_STKSZ]; \
- char DB_stack_guard[guardsize]; \
- char DB_stack[EXCEPTION_STKSZ]; \
- char MCE_stack_guard[guardsize]; \
- char MCE_stack[EXCEPTION_STKSZ]; \
- char IST_top_guard[guardsize]; \
+#define ESTACKS_MEMBERS(guardsize, db2_holesize, optional_stack_size) \
+ char DF_stack_guard[guardsize]; \
+ char DF_stack[EXCEPTION_STKSZ]; \
+ char NMI_stack_guard[guardsize]; \
+ char NMI_stack[EXCEPTION_STKSZ]; \
+ char DB2_stack_guard[guardsize]; \
+ char DB2_stack[db2_holesize]; \
+ char DB1_stack_guard[guardsize]; \
+ char DB1_stack[EXCEPTION_STKSZ]; \
+ char DB_stack_guard[guardsize]; \
+ char DB_stack[EXCEPTION_STKSZ]; \
+ char MCE_stack_guard[guardsize]; \
+ char MCE_stack[EXCEPTION_STKSZ]; \
+ char VC_stack_guard[guardsize]; \
+ char VC_stack[optional_stack_size]; \
+ char VC2_stack_guard[guardsize]; \
+ char VC2_stack[optional_stack_size]; \
+ char IST_top_guard[guardsize]; \
/* The exception stacks' physical storage. No guard pages required */
struct exception_stacks {
- ESTACKS_MEMBERS(0, 0)
+ ESTACKS_MEMBERS(0, 0, 0)
};
/* The effective cpu entry area mapping with guard pages. */
struct cea_exception_stacks {
- ESTACKS_MEMBERS(PAGE_SIZE, EXCEPTION_STKSZ)
+ ESTACKS_MEMBERS(PAGE_SIZE, EXCEPTION_STKSZ, EXCEPTION_STKSZ)
};
/*
@@ -45,6 +49,8 @@ enum exception_stack_ordering {
ESTACK_DB1,
ESTACK_DB,
ESTACK_MCE,
+ ESTACK_VC,
+ ESTACK_VC2,
N_EXCEPTION_STACKS
};
@@ -141,4 +147,7 @@ static inline struct entry_stack *cpu_en
#define __this_cpu_ist_top_va(name) \
CEA_ESTACK_TOP(__this_cpu_read(cea_exception_stacks), name)
+#define __this_cpu_ist_bottom_va(name) \
+ CEA_ESTACK_BOT(__this_cpu_read(cea_exception_stacks), name)
+
#endif
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -28,6 +28,7 @@
#define IST_INDEX_NMI 1
#define IST_INDEX_DB 2
#define IST_INDEX_MCE 3
+#define IST_INDEX_VC 4
/*
* Set __PAGE_OFFSET to the most negative possible address +
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1883,6 +1883,8 @@ void cpu_init(void)
t->x86_tss.ist[IST_INDEX_NMI] = __this_cpu_ist_top_va(NMI);
t->x86_tss.ist[IST_INDEX_DB] = __this_cpu_ist_top_va(DB);
t->x86_tss.ist[IST_INDEX_MCE] = __this_cpu_ist_top_va(MCE);
+ /* Only mapped when SEV-ES is active */
+ t->x86_tss.ist[IST_INDEX_VC] = __this_cpu_ist_top_va(VC);
}
t->x86_tss.io_bitmap_base = IO_BITMAP_OFFSET;
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -26,11 +26,13 @@ static const char * const exception_stac
[ ESTACK_DB1 ] = "#DB1",
[ ESTACK_DB ] = "#DB",
[ ESTACK_MCE ] = "#MC",
+ [ ESTACK_VC ] = "#VC",
+ [ ESTACK_VC2 ] = "#VC2",
};
const char *stack_type_name(enum stack_type type)
{
- BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
+ BUILD_BUG_ON(N_EXCEPTION_STACKS != 8);
if (type == STACK_TYPE_IRQ)
return "IRQ";
@@ -82,6 +84,8 @@ struct estack_pages estack_pages[CEA_EST
EPAGERANGE(DB1),
EPAGERANGE(DB),
EPAGERANGE(MCE),
+ EPAGERANGE(VC),
+ EPAGERANGE(VC2),
};
static bool in_exception_stack(unsigned long *stack, struct stack_info *info)
@@ -91,7 +95,7 @@ static bool in_exception_stack(unsigned
struct pt_regs *regs;
unsigned int k;
- BUILD_BUG_ON(N_EXCEPTION_STACKS != 6);
+ BUILD_BUG_ON(N_EXCEPTION_STACKS != 8);
begin = (unsigned long)__this_cpu_read(cea_exception_stacks);
/*
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -17,6 +17,7 @@
#include <linux/kernel.h>
#include <linux/mm.h>
+#include <asm/cpu_entry_area.h>
#include <asm/sev-es.h>
#include <asm/insn-eval.h>
#include <asm/fpu/internal.h>
@@ -37,10 +38,41 @@ static struct ghcb __initdata *boot_ghcb
/* #VC handler runtime per-CPU data */
struct sev_es_runtime_data {
struct ghcb ghcb_page;
+
+ /* Physical storage for the per-CPU IST stack of the #VC handler */
+ char ist_stack[EXCEPTION_STKSZ] __aligned(PAGE_SIZE);
+
+ /*
+ * Physical storage for the per-CPU fall-back stack of the #VC handler.
+ * The fall-back stack is used when it is not safe to switch back to the
+ * interrupted stack in the #VC entry code.
+ */
+ char fallback_stack[EXCEPTION_STKSZ] __aligned(PAGE_SIZE);
};
static DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data);
+static void __init setup_vc_stacks(int cpu)
+{
+ struct sev_es_runtime_data *data;
+ struct cpu_entry_area *cea;
+ unsigned long vaddr;
+ phys_addr_t pa;
+
+ data = per_cpu(runtime_data, cpu);
+ cea = get_cpu_entry_area(cpu);
+
+ /* Map #VC IST stack */
+ vaddr = CEA_ESTACK_BOT(&cea->estacks, VC);
+ pa = __pa(data->ist_stack);
+ cea_set_pte((void *)vaddr, pa, PAGE_KERNEL);
+
+ /* Map VC fall-back stack */
+ vaddr = CEA_ESTACK_BOT(&cea->estacks, VC2);
+ pa = __pa(data->fallback_stack);
+ cea_set_pte((void *)vaddr, pa, PAGE_KERNEL);
+}
+
/* Needed in vc_early_forward_exception */
void do_early_exception(struct pt_regs *regs, int trapnr);
@@ -249,6 +281,7 @@ void __init sev_es_init_vc_handling(void
for_each_possible_cpu(cpu) {
alloc_runtime_data(cpu);
init_ghcb(cpu);
+ setup_vc_stacks(cpu);
}
}