On 5/5/2023 12:59 PM, Gupta, Pankaj wrote:
Hi Tianyu,
I tried to understand some details of this patch. Please find below
some comments/questions.
Thanks,
Add a #HV exception handler that uses IST stack.
Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
---
Change since RFC V2:
* Remove unnecessary line in the change log.
---
arch/x86/entry/entry_64.S | 22 +++++++----
arch/x86/include/asm/cpu_entry_area.h | 6 +++
arch/x86/include/asm/idtentry.h | 40 +++++++++++++++++++-
arch/x86/include/asm/page_64_types.h | 1 +
arch/x86/include/asm/trapnr.h | 1 +
arch/x86/include/asm/traps.h | 1 +
arch/x86/kernel/cpu/common.c | 1 +
arch/x86/kernel/dumpstack_64.c | 9 ++++-
arch/x86/kernel/idt.c | 1 +
arch/x86/kernel/sev.c | 53 +++++++++++++++++++++++++++
arch/x86/kernel/traps.c | 40 ++++++++++++++++++++
arch/x86/mm/cpu_entry_area.c | 2 +
12 files changed, 165 insertions(+), 12 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index eccc3431e515..653b1f10699b 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -496,7 +496,7 @@ SYM_CODE_END(\asmsym)
#ifdef CONFIG_AMD_MEM_ENCRYPT
/**
- * idtentry_vc - Macro to generate entry stub for #VC
+ * idtentry_sev - Macro to generate entry stub for #VC
* @vector: Vector number
* @asmsym: ASM symbol for the entry point
* @cfunc: C function to be called
@@ -515,14 +515,18 @@ SYM_CODE_END(\asmsym)
*
* The macro is only used for one vector, but it is planned to be
extended in
* the future for the #HV exception.
- */
-.macro idtentry_vc vector asmsym cfunc
+*/
+.macro idtentry_sev vector asmsym cfunc has_error_code:req
SYM_CODE_START(\asmsym)
UNWIND_HINT_IRET_REGS
ENDBR
ASM_CLAC
cld
+ .if \vector == X86_TRAP_HV
+ pushq $-1 /* ORIG_RAX: no syscall */
+ .endif
+
/*
* If the entry is from userspace, switch stacks and treat it as
* a normal entry.
@@ -545,7 +549,12 @@ SYM_CODE_START(\asmsym)
* stack.
*/
movq %rsp, %rdi /* pt_regs pointer */
- call vc_switch_off_ist
+ .if \vector == X86_TRAP_VC
+ call vc_switch_off_ist
I think the stack switching logic is similar for #VC & #HV.
So, we can use common function. Just the corresponding fallback
stack switching is different. Maybe we can pass the hint as an
argument (%rsi?) to something like "sev_switch_off_ist()", and use
the corresponding (#HV or #VC) fallbacks stack?
Also, Please include the below patch from Ashish for #HV
reentrancy check.
https://github.com/ashkalra/linux/commit/6975484094b7cb8d703c45066780dd85043cd040
Thanks,
Pankaj
