On 8/29/2025 8:31 AM, Xin Li (Intel) wrote:
Convert the __this_cpu_ist_{top,bottom}_va() macros into proper functions,
and export __this_cpu_ist_top_va() to allow KVM to retrieve the top of the
per-CPU exception stack.
FRED introduced new fields in the host-state area of the VMCS for stack
levels 1->3 (HOST_IA32_FRED_RSP[123]), each respectively corresponding to
per-CPU exception stacks for #DB, NMI and #DF. KVM must populate these
fields each time a vCPU is loaded onto a CPU.
To simplify access to the exception stacks in struct cea_exception_stacks,
a union is used to create an array alias, enabling array-style indexing of
the stack entries.
After introducing array-style indexing, we can further simplify the code by
removing ESTACKS_MEMBERS() from struct cea_exception_stacks, as done in the
following patch. However, including this change in the current patch set
may be distracting, so I plan to submit it separately at a later time.
commit b305b83ab90c77242030727139c9b2e04f4de11e
Author: Xin Li (Intel) <xin@xxxxxxxxx>
Date: Fri Aug 29 12:22:35 2025 -0400
x86/cea: Simplify cea_exception_stacks by removing ESTACKS_MEMBERS()
With most accesses to cea_exception_stacks now using array-style indexing,
the ESTACKS_MEMBERS() macro is no longer necessary in cea_exception_stacks
and can be removed to streamline the structure and improve code
readability.
Remove the CEA_ESTACK_SIZE macro, which redundantly defines
EXCEPTION_STKSZ.
Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx>
diff --git a/arch/x86/include/asm/cpu_entry_area.h
b/arch/x86/include/asm/cpu_entry_area.h
index 58cd71144e5e..509e52fc3a0f 100644
--- a/arch/x86/include/asm/cpu_entry_area.h
+++ b/arch/x86/include/asm/cpu_entry_area.h
@@ -52,22 +52,15 @@ struct exception_stacks {
/* The effective cpu entry area mapping with guard pages. */
struct cea_exception_stacks {
- union{
- struct {
- ESTACKS_MEMBERS(PAGE_SIZE, EXCEPTION_STKSZ)
- };
- struct {
- char stack_guard[PAGE_SIZE];
- char stack[EXCEPTION_STKSZ];
- } event_stacks[N_EXCEPTION_STACKS];
- };
+ struct {
+ char stack_guard[PAGE_SIZE];
+ char stack[EXCEPTION_STKSZ];
+ } event_stacks[N_EXCEPTION_STACKS];
+ char IST_top_guard[PAGE_SIZE];
};
-#define CEA_ESTACK_SIZE(st) \
- sizeof(((struct cea_exception_stacks *)0)->st## _stack)
-
#define CEA_ESTACK_OFFS(st) \
- offsetof(struct cea_exception_stacks, st## _stack)
+ offsetof(struct cea_exception_stacks, event_stacks[st].stack)
#define CEA_ESTACK_PAGES \
(sizeof(struct cea_exception_stacks) / PAGE_SIZE)
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 40f51e278171..93b10b264e53 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -70,9 +70,9 @@ struct estack_pages {
#define EPAGERANGE(st) \
[PFN_DOWN(CEA_ESTACK_OFFS(st)) ... \
- PFN_DOWN(CEA_ESTACK_OFFS(st) + CEA_ESTACK_SIZE(st) - 1)] = { \
+ PFN_DOWN(CEA_ESTACK_OFFS(st) + EXCEPTION_STKSZ - 1)] = { \
.offs = CEA_ESTACK_OFFS(st), \
- .size = CEA_ESTACK_SIZE(st), \
+ .size = EXCEPTION_STKSZ, \
.type = STACK_TYPE_EXCEPTION + st, }
/*
diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
index 595c2e03ddd5..de0deb8b824c 100644
--- a/arch/x86/mm/cpu_entry_area.c
+++ b/arch/x86/mm/cpu_entry_area.c
@@ -157,7 +157,7 @@ static void __init percpu_setup_debug_store(unsigned
int cpu)
#define cea_map_stack(name) do { \
npages = sizeof(estacks->name## _stack) / PAGE_SIZE; \
- cea_map_percpu_pages(cea->estacks.name## _stack, \
+ cea_map_percpu_pages(cea->estacks.event_stacks[name].stack, \
estacks->name## _stack, npages, PAGE_KERNEL); \
} while (0)
