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Date: Mon, 4 Oct 2021 17:08:39 +0200
From: Borislav Petkov <bp@...en8.de>
To: Joerg Roedel <jroedel@...e.de>
Cc: Tom Lendacky <thomas.lendacky@....com>,
linux-kernel@...r.kernel.org, x86@...nel.org,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Brijesh Singh <brijesh.singh@....com>
Subject: [PATCH] x86/sev: Make the #VC exception stacks part of the default
stacks storage
---
From: Borislav Petkov <bp@...e.de>
Date: Fri, 1 Oct 2021 21:41:20 +0200
The size of the exception stacks was increased by the commit in Fixes,
resulting in stack sizes greater than a page in size. The #VC exception
handling was only mapping the first (bottom) page, resulting in an
SEV-ES guest failing to boot.
Make the #VC exception stacks part of the default exception stacks
storage and allocate them with a CONFIG_AMD_MEM_ENCRYPT=y .config. Map
them only when a SEV-ES guest has been detected.
Rip out the custom VC stacks mapping and storage code.
[ bp: Steal and adapt Tom's commit message. ]
Fixes: 7fae4c24a2b8 ("x86: Increase exception stack sizes")
Signed-off-by: Borislav Petkov <bp@...e.de>
---
arch/x86/include/asm/cpu_entry_area.h | 16 +++++++++-----
arch/x86/kernel/sev.c | 32 ---------------------------
arch/x86/mm/cpu_entry_area.c | 7 ++++++
3 files changed, 18 insertions(+), 37 deletions(-)
diff --git a/arch/x86/include/asm/cpu_entry_area.h b/arch/x86/include/asm/cpu_entry_area.h
index 3d52b094850a..2512e1f5ac02 100644
--- a/arch/x86/include/asm/cpu_entry_area.h
+++ b/arch/x86/include/asm/cpu_entry_area.h
@@ -10,8 +10,14 @@
#ifdef CONFIG_X86_64
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+#define VC_EXCEPTION_STKSZ EXCEPTION_STKSZ
+#else
+#define VC_EXCEPTION_STKSZ 0
+#endif
+
/* Macro to enforce the same ordering and stack sizes */
-#define ESTACKS_MEMBERS(guardsize, optional_stack_size) \
+#define ESTACKS_MEMBERS(guardsize) \
char DF_stack_guard[guardsize]; \
char DF_stack[EXCEPTION_STKSZ]; \
char NMI_stack_guard[guardsize]; \
@@ -21,19 +27,19 @@
char MCE_stack_guard[guardsize]; \
char MCE_stack[EXCEPTION_STKSZ]; \
char VC_stack_guard[guardsize]; \
- char VC_stack[optional_stack_size]; \
+ char VC_stack[VC_EXCEPTION_STKSZ]; \
char VC2_stack_guard[guardsize]; \
- char VC2_stack[optional_stack_size]; \
+ char VC2_stack[VC_EXCEPTION_STKSZ]; \
char IST_top_guard[guardsize]; \
/* The exception stacks' physical storage. No guard pages required */
struct exception_stacks {
- ESTACKS_MEMBERS(0, 0)
+ ESTACKS_MEMBERS(0)
};
/* The effective cpu entry area mapping with guard pages. */
struct cea_exception_stacks {
- ESTACKS_MEMBERS(PAGE_SIZE, EXCEPTION_STKSZ)
+ ESTACKS_MEMBERS(PAGE_SIZE)
};
/*
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index a6895e440bc3..88401675dabb 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -46,16 +46,6 @@ static struct ghcb __initdata *boot_ghcb;
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);
-
/*
* Reserve one page per CPU as backup storage for the unencrypted GHCB.
* It is needed when an NMI happens while the #VC handler uses the real
@@ -99,27 +89,6 @@ DEFINE_STATIC_KEY_FALSE(sev_es_enable_key);
/* Needed in vc_early_forward_exception */
void do_early_exception(struct pt_regs *regs, int trapnr);
-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);
-}
-
static __always_inline bool on_vc_stack(struct pt_regs *regs)
{
unsigned long sp = regs->sp;
@@ -787,7 +756,6 @@ void __init sev_es_init_vc_handling(void)
for_each_possible_cpu(cpu) {
alloc_runtime_data(cpu);
init_ghcb(cpu);
- setup_vc_stacks(cpu);
}
sev_es_setup_play_dead();
diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
index f5e1e60c9095..82d062414f19 100644
--- a/arch/x86/mm/cpu_entry_area.c
+++ b/arch/x86/mm/cpu_entry_area.c
@@ -110,6 +110,13 @@ static void __init percpu_setup_exception_stacks(unsigned int cpu)
cea_map_stack(NMI);
cea_map_stack(DB);
cea_map_stack(MCE);
+
+ if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
+ if (sev_es_active()) {
+ cea_map_stack(VC);
+ cea_map_stack(VC2);
+ }
+ }
}
#else
static inline void percpu_setup_exception_stacks(unsigned int cpu)
--
2.29.2
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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