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Subject[PATCH V6 44/49] x86/sev: Add and use ist_vc_switch_off_ist()
Date
From: Lai Jiangshan <laijs@linux.alibaba.com>

ist_vc_switch_off_ist() is the same as vc_switch_off_ist(), but it is
called without CR3 or gsbase fixed. It has to call ist_paranoid_entry()
by its own.

It is prepared for using C code for the other part of identry_vc and
remove ASM paranoid_entry() and paranoid_exit().

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
arch/x86/entry/entry_64.S | 20 ++++++++++----------
arch/x86/include/asm/traps.h | 3 ++-
arch/x86/kernel/traps.c | 14 +++++++++++++-
3 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 5a9738218722..b18df736b981 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -515,26 +515,26 @@ SYM_CODE_START(\asmsym)
testb $3, CS(%rsp)
jnz .Lfrom_usermode_switch_stack_\@

- /*
- * paranoid_entry returns SWAPGS flag for paranoid_exit in EBX.
- * EBX == 0 -> SWAPGS, EBX == 1 -> no SWAPGS
- */
- call paranoid_entry
-
- UNWIND_HINT_REGS
-
/*
* Switch off the IST stack to make it free for nested exceptions. The
- * vc_switch_off_ist() function will switch back to the interrupted
+ * ist_vc_switch_off_ist() function will switch back to the interrupted
* stack if it is safe to do so. If not it switches to the VC fall-back
* stack.
*/
movq %rsp, %rdi /* pt_regs pointer */
- call vc_switch_off_ist
+ call ist_vc_switch_off_ist
movq %rax, %rsp /* Switch to new stack */

UNWIND_HINT_REGS

+ /*
+ * paranoid_entry returns SWAPGS flag for paranoid_exit in EBX.
+ * EBX == 0 -> SWAPGS, EBX == 1 -> no SWAPGS
+ */
+ call paranoid_entry
+
+ UNWIND_HINT_REGS
+
/* Update pt_regs */
movq ORIG_RAX(%rsp), %rsi /* get error code into 2nd argument*/
movq $-1, ORIG_RAX(%rsp) /* no syscall to restart */
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 686461ac9803..1aefc081d763 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -16,7 +16,8 @@ asmlinkage __visible notrace
struct pt_regs *fixup_bad_iret(struct pt_regs *bad_regs);
asmlinkage __visible notrace struct pt_regs *error_entry(struct pt_regs *eregs);
void __init trap_init(void);
-asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *eregs);
+asmlinkage __visible __entry_text
+struct pt_regs *ist_vc_switch_off_ist(struct pt_regs *eregs);
#endif

#ifdef CONFIG_X86_F00F_BUG
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 4e9d306f313c..1a84587cb4c7 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -717,7 +717,7 @@ asmlinkage __visible noinstr struct pt_regs *sync_regs(struct pt_regs *eregs)
}

#ifdef CONFIG_AMD_MEM_ENCRYPT
-asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *regs)
+static noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *regs)
{
unsigned long sp, *stack;
struct stack_info info;
@@ -757,6 +757,18 @@ asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *r

return regs_ret;
}
+
+asmlinkage __visible __entry_text
+struct pt_regs *ist_vc_switch_off_ist(struct pt_regs *regs)
+{
+ unsigned long cr3, gsbase;
+
+ ist_paranoid_entry(&cr3, &gsbase);
+ regs = vc_switch_off_ist(regs);
+ ist_paranoid_exit(cr3, gsbase);
+
+ return regs;
+}
#endif

asmlinkage __visible noinstr
--
2.19.1.6.gb485710b
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