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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] x86/entry: Use PUSH_AND_CLEAR_GPRS and drop SAVE_ALL
commit c4bf5bc5f0edbcbc5965c924db069483b2cf6049
Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Jul 6 15:59:40 2026 +0100
Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Jul 7 17:19:38 2026 +0100
x86/entry: Use PUSH_AND_CLEAR_GPRS and drop SAVE_ALL
PUSH_AND_CLEAR_GPRS is shorter than SAVE_ALL in terms of emitted code.
lstar_enter() and cstar_enter() do not need CLD. The SYSCALL instruction
sanitises flags based on MSR_SYSCALL_MASK. For all other cases, place the
CLD
instruction next to STAC/CLAC so the flag handling is together.
Get rid of the compat=1 special case for PV32. It's not obviously a win,
and
PV32 is getting increasingly rare these days.
No functional change.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
xen/arch/x86/include/asm/asm_defns.h | 45 ------------------------------------
xen/arch/x86/x86_64/compat/entry.S | 4 +++-
xen/arch/x86/x86_64/entry.S | 25 ++++++++++++--------
3 files changed, 19 insertions(+), 55 deletions(-)
diff --git a/xen/arch/x86/include/asm/asm_defns.h
b/xen/arch/x86/include/asm/asm_defns.h
index d1b80186c1..6c65acd083 100644
--- a/xen/arch/x86/include/asm/asm_defns.h
+++ b/xen/arch/x86/include/asm/asm_defns.h
@@ -219,51 +219,6 @@ static always_inline void stac(void)
#endif
#ifdef __ASSEMBLER__
-.macro SAVE_ALL compat=0
- addq $-(UREGS_error_code-UREGS_r15), %rsp
- cld
- movq %rdi,UREGS_rdi(%rsp)
- xor %edi, %edi
- movq %rsi,UREGS_rsi(%rsp)
- xor %esi, %esi
- movq %rdx,UREGS_rdx(%rsp)
- xor %edx, %edx
- movq %rcx,UREGS_rcx(%rsp)
- xor %ecx, %ecx
- movq %rax,UREGS_rax(%rsp)
- xor %eax, %eax
-.if !\compat
- movq %r8,UREGS_r8(%rsp)
- movq %r9,UREGS_r9(%rsp)
- movq %r10,UREGS_r10(%rsp)
- movq %r11,UREGS_r11(%rsp)
-.endif
- xor %r8d, %r8d
- xor %r9d, %r9d
- xor %r10d, %r10d
- xor %r11d, %r11d
- movq %rbx,UREGS_rbx(%rsp)
- xor %ebx, %ebx
- movq %rbp,UREGS_rbp(%rsp)
-#ifdef CONFIG_FRAME_POINTER
-/* Indicate special exception stack frame by inverting the frame pointer. */
- leaq UREGS_rbp(%rsp), %rbp
- notq %rbp
-#else
- xor %ebp, %ebp
-#endif
-.if !\compat
- movq %r12,UREGS_r12(%rsp)
- movq %r13,UREGS_r13(%rsp)
- movq %r14,UREGS_r14(%rsp)
- movq %r15,UREGS_r15(%rsp)
-.endif
- xor %r12d, %r12d
- xor %r13d, %r13d
- xor %r14d, %r14d
- xor %r15d, %r15d
-.endm
-
/*
* Push and clear GPRs
*/
diff --git a/xen/arch/x86/x86_64/compat/entry.S
b/xen/arch/x86/x86_64/compat/entry.S
index 4bf4ee7c94..ca20ea12f9 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -11,12 +11,14 @@
#include <asm/desc.h>
#include <public/xen.h>
+/* DPL1 gate, restricted to 32bit PV guest kernels only. */
FUNC(entry_int82)
ENDBR64
+ cld
ALTERNATIVE "", clac, X86_FEATURE_XEN_SMAP
pushq $0
movb $HYPERCALL_VECTOR, EFRAME_entry_vector(%rsp)
- SAVE_ALL compat=1 /* DPL1 gate, restricted to 32bit PV guests only. */
+ PUSH_AND_CLEAR_GPRS
GET_STACK_END(14)
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index cd3532d7d1..22729b1f43 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -305,7 +305,7 @@ FUNC(lstar_enter)
pushq $0
BUILD_BUG_ON(TRAP_syscall & 0xff)
movb $TRAP_syscall >> 8, EFRAME_entry_vector + 1(%rsp)
- SAVE_ALL
+ PUSH_AND_CLEAR_GPRS
GET_STACK_END(14)
@@ -345,7 +345,7 @@ FUNC(cstar_enter)
pushq $0
BUILD_BUG_ON(TRAP_syscall & 0xff)
movb $TRAP_syscall >> 8, EFRAME_entry_vector + 1(%rsp)
- SAVE_ALL
+ PUSH_AND_CLEAR_GPRS
GET_STACK_END(14)
@@ -383,13 +383,14 @@ FUNC(sysenter_entry)
pushq $0
pushfq
LABEL(sysenter_eflags_saved, 0)
+ cld
ALTERNATIVE "", clac, X86_FEATURE_XEN_SMAP
pushq $3 /* ring 3 null cs */
pushq $0 /* null rip */
pushq $0
BUILD_BUG_ON(TRAP_syscall & 0xff)
movb $TRAP_syscall >> 8, EFRAME_entry_vector + 1(%rsp)
- SAVE_ALL
+ PUSH_AND_CLEAR_GPRS
GET_STACK_END(14)
@@ -442,10 +443,11 @@ END(sysenter_entry)
FUNC(entry_int80)
ENDBR64
+ cld
ALTERNATIVE "", clac, X86_FEATURE_XEN_SMAP
pushq $0
movb $0x80, EFRAME_entry_vector(%rsp)
- SAVE_ALL
+ PUSH_AND_CLEAR_GPRS
GET_STACK_END(14)
@@ -722,8 +724,9 @@ END(ret_from_intr)
.section .init.text, "ax", @progbits
FUNC(early_page_fault)
ENDBR64
+ cld
movb $X86_EXC_PF, EFRAME_entry_vector(%rsp)
- SAVE_ALL
+ PUSH_AND_CLEAR_GPRS
movq %rsp, %rdi
call do_early_page_fault
jmp restore_all_xen
@@ -769,8 +772,9 @@ UNLIKELY_END(exit_cr3)
END(restore_all_xen)
FUNC(common_interrupt)
+ cld
ALTERNATIVE "", clac, X86_FEATURE_XEN_SMAP
- SAVE_ALL
+ PUSH_AND_CLEAR_GPRS
GET_STACK_END(14)
@@ -805,8 +809,9 @@ FUNC(entry_PF)
END(entry_PF)
/* No special register assumptions. */
FUNC(handle_exception, 0)
+ cld
ALTERNATIVE "", clac, X86_FEATURE_XEN_SMAP
- SAVE_ALL
+ PUSH_AND_CLEAR_GPRS
GET_STACK_END(14)
@@ -1103,9 +1108,10 @@ END(entry_CP)
FUNC(entry_DF)
ENDBR64
movb $X86_EXC_DF, EFRAME_entry_vector(%rsp)
+ cld
/* Set AC to reduce chance of further SMAP faults */
ALTERNATIVE "", stac, X86_FEATURE_XEN_SMAP
- SAVE_ALL
+ PUSH_AND_CLEAR_GPRS
GET_STACK_END(14)
@@ -1132,8 +1138,9 @@ FUNC(entry_NMI)
END(entry_NMI)
FUNC(handle_ist_exception)
+ cld
ALTERNATIVE "", clac, X86_FEATURE_XEN_SMAP
- SAVE_ALL
+ PUSH_AND_CLEAR_GPRS
GET_STACK_END(14)
--
generated by git-patchbot for /home/xen/git/xen.git#staging
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