[PATCH 1/4] x86/pv: Drop int80_bounce from struct pv_vcpu

[Andrew Cooper <andrew.cooper3@citrix.com>]

The int80_bounce field of struct pv_vcpu is a bit of an odd special case,
because it is a simple derivation of trap_ctxt[0x80], which is also stored.

It is also the only use of {compat_,}create_bounce_frame() which isn't
referencing the plain trap_bounce field of struct pv_vcpu.  (And altering this
property the purpose of this patch.)

Remove the int80_bounce field entirely, along with init_int80_direct_trap(),
which in turn requires that the int80_direct_trap() path gain logic previously
contained in init_int80_direct_trap().

This does admittedly make the int80 fastpath slightly longer, but these few
instructions are in the noise compared to the architectural context switch
overhead, and it now matches the syscall/sysenter paths (which have far less
architectural overhead already).

No behavioural change from the guests point of view.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
---
 xen/arch/x86/domain.c              |  2 --
 xen/arch/x86/traps.c               |  4 ----
 xen/arch/x86/x86_64/asm-offsets.c  |  1 -
 xen/arch/x86/x86_64/compat/traps.c |  4 ----
 xen/arch/x86/x86_64/entry.S        | 32 ++++++++++++++++++++++++++++----
 xen/arch/x86/x86_64/traps.c        | 14 --------------
 xen/include/asm-x86/domain.h       |  1 -
 xen/include/asm-x86/processor.h    |  2 --
 8 files changed, 28 insertions(+), 32 deletions(-)

diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 2ef1c9f..7b301e3 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -833,8 +833,6 @@ int arch_set_info_guest(
         goto out;
     }
 
-    init_int80_direct_trap(v);
-
     /* IOPL privileges are virtualised. */
     v->arch.pv_vcpu.iopl = v->arch.user_regs.eflags & X86_EFLAGS_IOPL;
     v->arch.user_regs.eflags &= ~X86_EFLAGS_IOPL;
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 27fdf12..ece2c13 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -4013,7 +4013,6 @@ long do_set_trap_table(XEN_GUEST_HANDLE_PARAM(const_trap_info_t) traps)
     if ( guest_handle_is_null(traps) )
     {
         memset(dst, 0, NR_VECTORS * sizeof(*dst));
-        init_int80_direct_trap(curr);
         return 0;
     }
 
@@ -4035,9 +4034,6 @@ long do_set_trap_table(XEN_GUEST_HANDLE_PARAM(const_trap_info_t) traps)
 
         memcpy(&dst[cur.vector], &cur, sizeof(cur));
 
-        if ( cur.vector == 0x80 )
-            init_int80_direct_trap(curr);
-
         guest_handle_add_offset(traps, 1);
 
         if ( hypercall_preempt_check() )
diff --git a/xen/arch/x86/x86_64/asm-offsets.c b/xen/arch/x86/x86_64/asm-offsets.c
index e136af6..adf2749 100644
--- a/xen/arch/x86/x86_64/asm-offsets.c
+++ b/xen/arch/x86/x86_64/asm-offsets.c
@@ -61,7 +61,6 @@ void __dummy__(void)
     OFFSET(VCPU_domain, struct vcpu, domain);
     OFFSET(VCPU_vcpu_info, struct vcpu, vcpu_info);
     OFFSET(VCPU_trap_bounce, struct vcpu, arch.pv_vcpu.trap_bounce);
-    OFFSET(VCPU_int80_bounce, struct vcpu, arch.pv_vcpu.int80_bounce);
     OFFSET(VCPU_thread_flags, struct vcpu, arch.flags);
     OFFSET(VCPU_event_addr, struct vcpu, arch.pv_vcpu.event_callback_eip);
     OFFSET(VCPU_event_sel, struct vcpu, arch.pv_vcpu.event_callback_cs);
diff --git a/xen/arch/x86/x86_64/compat/traps.c b/xen/arch/x86/x86_64/compat/traps.c
index 1751ec6..0ab2c31 100644
--- a/xen/arch/x86/x86_64/compat/traps.c
+++ b/xen/arch/x86/x86_64/compat/traps.c
@@ -339,7 +339,6 @@ int compat_set_trap_table(XEN_GUEST_HANDLE(trap_info_compat_t) traps)
     if ( guest_handle_is_null(traps) )
     {
         memset(dst, 0, NR_VECTORS * sizeof(*dst));
-        init_int80_direct_trap(current);
         return 0;
     }
 
@@ -358,9 +357,6 @@ int compat_set_trap_table(XEN_GUEST_HANDLE(trap_info_compat_t) traps)
 
         XLAT_trap_info(dst + cur.vector, &cur);
 
-        if ( cur.vector == 0x80 )
-            init_int80_direct_trap(current);
-
         guest_handle_add_offset(traps, 1);
 
         if ( hypercall_preempt_check() )
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 65c771f..57952d0 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -233,12 +233,36 @@ UNLIKELY_END(msi_check)
 
         GET_CURRENT(bx)
 
-        /* Check that the callback is non-null. */
-        leaq  VCPU_int80_bounce(%rbx),%rdx
-        cmpb  $0,TRAPBOUNCE_flags(%rdx)
+        mov   VCPU_trap_ctxt(%rbx), %rsi
+        mov   VCPU_domain(%rbx), %rax
+
+        /*
+         * if ( null_trap_bounce(v, &v->arch.pv_vcpu.trap_ctxt[0x80]) )
+         *    goto int80_slow_path;
+         */
+        mov    0x80 * TRAPINFO_sizeof + TRAPINFO_eip(%rsi), %rdi
+        movzwl 0x80 * TRAPINFO_sizeof + TRAPINFO_cs (%rsi), %ecx
+
+        mov   %ecx, %edx
+        and   $~3, %edx
+
+        testb $1, DOMAIN_is_32bit_pv(%rax)
+        cmove %rdi, %rdx
+
+        test  %rdx, %rdx
         jz    int80_slow_path
 
-        movq  VCPU_domain(%rbx),%rax
+        /* Construct trap_bounce from trap_ctxt[0x80]. */
+        lea   VCPU_trap_bounce(%rbx), %rdx
+        movw  %cx, TRAPBOUNCE_cs(%rdx)
+        movq  %rdi, TRAPBOUNCE_eip(%rdx)
+
+        /* TB_flags = TBF_EXCEPTION | (TI_GET_IF(ti) ? TBF_INTERRUPT : 0); */
+        testb $4, 0x80 * TRAPINFO_sizeof + TRAPINFO_flags(%rsi)
+        setnz %cl
+        lea   TBF_EXCEPTION(, %rcx, TBF_INTERRUPT), %ecx
+        movb  %cl, TRAPBOUNCE_flags(%rdx)
+
         testb $1,DOMAIN_is_32bit_pv(%rax)
         jnz   compat_int80_direct_trap
 
diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
index 78f4105..69f1dc2 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -422,20 +422,6 @@ void subarch_percpu_traps_init(void)
     wrmsrl(MSR_SYSCALL_MASK, XEN_SYSCALL_MASK);
 }
 
-void init_int80_direct_trap(struct vcpu *v)
-{
-    struct trap_info *ti = &v->arch.pv_vcpu.trap_ctxt[0x80];
-    struct trap_bounce *tb = &v->arch.pv_vcpu.int80_bounce;
-
-    tb->cs    = ti->cs;
-    tb->eip   = ti->address;
-
-    if ( null_trap_bounce(v, tb) )
-        tb->flags = 0;
-    else
-        tb->flags = TBF_EXCEPTION | (TI_GET_IF(ti) ? TBF_INTERRUPT : 0);
-}
-
 static long register_guest_callback(struct callback_register *reg)
 {
     long ret = 0;
diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index 6ab987f..ece016b 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -473,7 +473,6 @@ struct pv_vcpu
 
     /* Bounce information for propagating an exception to guest OS. */
     struct trap_bounce trap_bounce;
-    struct trap_bounce int80_bounce;
 
     /* I/O-port access bitmap. */
     XEN_GUEST_HANDLE(uint8) iobmp; /* Guest kernel vaddr of the bitmap. */
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 1d1a4ff..50435e3 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -466,8 +466,6 @@ extern idt_entry_t *idt_tables[];
 
 DECLARE_PER_CPU(struct tss_struct, init_tss);
 
-extern void init_int80_direct_trap(struct vcpu *v);
-
 extern void write_ptbase(struct vcpu *v);
 
 void destroy_gdt(struct vcpu *d);
-- 
2.1.4


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