x86: drop failsafe callback invocation from assembly

Afaict this was never necessary on a 64-bit hypervisor, and was instead
just blindly cloned over from 32-bit code: We don't fiddle with (and
hence don't reload) any of DS, ES, FS, or GS, and an exception on IRET
itself can equally well be reported to the guest as that very exception
on the target of that IRET.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/x86_64/compat/entry.S b/xen/arch/x86/x86_64/compat/entry.S
index 3088aa7651155fe90213921b5d656d8a4d84e84f..8cb8bca6695ea67d79708be7fcffa92029b4c283 100644 (file)
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -176,39 +176,7 @@ ENTRY(compat_restore_all_guest)
         ASSERT_INTERRUPTS_DISABLED
         RESTORE_ALL adj=8 compat=1
 .Lft0:  iretq
-
-.section .fixup,"ax"
-.Lfx0:  sti
-        SAVE_ALL
-        movq  UREGS_error_code(%rsp),%rsi
-        movq  %rsp,%rax
-        andq  $~0xf,%rsp
-        pushq $__HYPERVISOR_DS         # SS
-        pushq %rax                     # RSP
-        pushfq                         # RFLAGS
-        pushq $__HYPERVISOR_CS         # CS
-        leaq  .Ldf0(%rip),%rax
-        pushq %rax                     # RIP
-        pushq %rsi                     # error_code/entry_vector
-        jmp   handle_exception
-.Ldf0:  GET_CURRENT(%rbx)
-        jmp   compat_test_all_events
-compat_failsafe_callback:
-        GET_CURRENT(%rbx)
-        leaq  VCPU_trap_bounce(%rbx),%rdx
-        movl  VCPU_failsafe_addr(%rbx),%eax
-        movl  %eax,TRAPBOUNCE_eip(%rdx)
-        movl  VCPU_failsafe_sel(%rbx),%eax
-        movw  %ax,TRAPBOUNCE_cs(%rdx)
-        movb  $TBF_FAILSAFE,TRAPBOUNCE_flags(%rdx)
-        btq   $_VGCF_failsafe_disables_events,VCPU_guest_context_flags(%rbx)
-        jnc   1f
-        orb   $TBF_INTERRUPT,TRAPBOUNCE_flags(%rdx)
-1:      call  compat_create_bounce_frame
-        jmp   compat_test_all_events
-.previous
-        _ASM_PRE_EXTABLE(.Lft0, .Lfx0)
-        _ASM_EXTABLE(.Ldf0, compat_failsafe_callback)
+        _ASM_PRE_EXTABLE(.Lft0, handle_exception)
 
 /* %rdx: trap_bounce, %rbx: struct vcpu */
 ENTRY(compat_post_handle_exception)
@@ -322,17 +290,6 @@ compat_create_bounce_frame:
         movl  TRAPBOUNCE_error_code(%rdx),%eax
 .Lft8:  movl  %eax,%fs:(%rsi)           # ERROR CODE
 1:
-        testb $TBF_FAILSAFE,%cl
-UNLIKELY_START(nz, compat_bounce_failsafe)
-        subl  $4*4,%esi
-        movl  %gs,%eax
-.Lft9:  movl  %eax,%fs:3*4(%rsi)        # GS
-.Lft10: movl  %edi,%fs:2*4(%rsi)        # FS
-        movl  %es,%eax
-.Lft11: movl  %eax,%fs:1*4(%rsi)        # ES
-        movl  %ds,%eax
-.Lft12: movl  %eax,%fs:0*4(%rsi)        # DS
-UNLIKELY_END(compat_bounce_failsafe)
         /* Rewrite our stack frame and return to guest-OS mode. */
         /* IA32 Ref. Vol. 3: TF, VM, RF and NT flags are cleared on trap. */
         andl  $~(X86_EFLAGS_VM|X86_EFLAGS_RF|\
@@ -364,14 +321,8 @@ __UNLIKELY_END(compat_bounce_null_selector)
         _ASM_EXTABLE(.Lft6,  compat_crash_page_fault_8)
         _ASM_EXTABLE(.Lft7,  compat_crash_page_fault)
         _ASM_EXTABLE(.Lft8,  compat_crash_page_fault)
-        _ASM_EXTABLE(.Lft9,  compat_crash_page_fault_12)
-        _ASM_EXTABLE(.Lft10, compat_crash_page_fault_8)
-        _ASM_EXTABLE(.Lft11, compat_crash_page_fault_4)
-        _ASM_EXTABLE(.Lft12, compat_crash_page_fault)
         _ASM_EXTABLE(.Lft13, .Lfx13)
 
-compat_crash_page_fault_12:
-        addl  $4,%esi
 compat_crash_page_fault_8:
         addl  $4,%esi
 compat_crash_page_fault_4:

diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 94a54aa7f2cb1361a877a8670880509c4fd9c7d2..fc81a93bf11d714e2c87828158ea6933d97088a4 100644 (file)
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -64,37 +64,7 @@ restore_all_guest:
 iret_exit_to_guest:
         addq  $8,%rsp
 .Lft0:  iretq
-
-.section .fixup,"ax"
-.Lfx0:  sti
-        SAVE_ALL
-        movq  UREGS_error_code(%rsp),%rsi
-        movq  %rsp,%rax
-        andq  $~0xf,%rsp
-        pushq $__HYPERVISOR_DS         # SS
-        pushq %rax                     # RSP
-        pushfq                         # RFLAGS
-        pushq $__HYPERVISOR_CS         # CS
-        leaq  .Ldf0(%rip),%rax
-        pushq %rax                     # RIP
-        pushq %rsi                     # error_code/entry_vector
-        jmp   handle_exception
-.Ldf0:  GET_CURRENT(%rbx)
-        jmp   test_all_events
-failsafe_callback:
-        GET_CURRENT(%rbx)
-        leaq  VCPU_trap_bounce(%rbx),%rdx
-        movq  VCPU_failsafe_addr(%rbx),%rax
-        movq  %rax,TRAPBOUNCE_eip(%rdx)
-        movb  $TBF_FAILSAFE,TRAPBOUNCE_flags(%rdx)
-        bt    $_VGCF_failsafe_disables_events,VCPU_guest_context_flags(%rbx)
-        jnc   1f
-        orb   $TBF_INTERRUPT,TRAPBOUNCE_flags(%rdx)
-1:      call  create_bounce_frame
-        jmp   test_all_events
-.previous
-        _ASM_PRE_EXTABLE(.Lft0, .Lfx0)
-        _ASM_EXTABLE(.Ldf0, failsafe_callback)
+        _ASM_PRE_EXTABLE(.Lft0, handle_exception)
 
         ALIGN
 /* No special register assumptions. */
@@ -405,18 +375,7 @@ __UNLIKELY_END(create_bounce_frame_bad_sp)
         subq  $8,%rsi
         movl  TRAPBOUNCE_error_code(%rdx),%eax
 .Lft7:  movq  %rax,(%rsi)               # ERROR CODE
-1:      testb $TBF_FAILSAFE,%cl
-UNLIKELY_START(nz, bounce_failsafe)
-        subq  $32,%rsi
-        movl  %gs,%eax
-.Lft8:  movq  %rax,24(%rsi)             # GS
-        movl  %fs,%eax
-.Lft9:  movq  %rax,16(%rsi)             # FS
-        movl  %es,%eax
-.Lft10: movq  %rax,8(%rsi)              # ES
-        movl  %ds,%eax
-.Lft11: movq  %rax,(%rsi)               # DS
-UNLIKELY_END(bounce_failsafe)
+1:
         subq  $16,%rsi
         movq  UREGS_r11+8(%rsp),%rax
 .Lft12: movq  %rax,8(%rsi)              # R11
@@ -446,10 +405,6 @@ __UNLIKELY_END(create_bounce_frame_bad_bounce_ip)
         _ASM_EXTABLE(.Lft5,  domain_crash_page_fault_16)
         _ASM_EXTABLE(.Lft6,  domain_crash_page_fault)
         _ASM_EXTABLE(.Lft7,  domain_crash_page_fault)
-        _ASM_EXTABLE(.Lft8,  domain_crash_page_fault_24)
-        _ASM_EXTABLE(.Lft9,  domain_crash_page_fault_16)
-        _ASM_EXTABLE(.Lft10, domain_crash_page_fault_8)
-        _ASM_EXTABLE(.Lft11, domain_crash_page_fault)
         _ASM_EXTABLE(.Lft12, domain_crash_page_fault_8)
         _ASM_EXTABLE(.Lft13, domain_crash_page_fault)
 

diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 271340e2917380f90af9274246448f707c8b4bbe..97907b2d9d72dcc4cc10ba47f56f86c14992fd9a 100644 (file)
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -128,7 +128,6 @@
 #define TBF_EXCEPTION          1
 #define TBF_EXCEPTION_ERRCODE  2
 #define TBF_INTERRUPT          8
-#define TBF_FAILSAFE          16
 
 /* 'arch_vcpu' flags values */
 #define _TF_kernel_mode        0