[PATCH 03/10] x86/spec_ctrl: Merge bti_ist_info and use_shadow_spec_ctrl into spec_ctrl_flags

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

All 3 bits of information here are control flags for the entry/exit code
behaviour.  Treat them as such, rather than having two different variables.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Juergen Gross <jgross@suse.com>
---
 xen/arch/x86/acpi/power.c           |  4 ++--
 xen/arch/x86/spec_ctrl.c            | 10 ++++----
 xen/arch/x86/x86_64/asm-offsets.c   |  3 +--
 xen/include/asm-x86/current.h       |  3 +--
 xen/include/asm-x86/spec_ctrl.h     | 10 ++++----
 xen/include/asm-x86/spec_ctrl_asm.h | 46 ++++++++++++++++++++-----------------
 6 files changed, 40 insertions(+), 36 deletions(-)

diff --git a/xen/arch/x86/acpi/power.c b/xen/arch/x86/acpi/power.c
index bb0d095..a704c7c 100644
--- a/xen/arch/x86/acpi/power.c
+++ b/xen/arch/x86/acpi/power.c
@@ -215,7 +215,7 @@ static int enter_state(u32 state)
     ci = get_cpu_info();
     spec_ctrl_enter_idle(ci);
     /* Avoid NMI/#MC using MSR_SPEC_CTRL until we've reloaded microcode. */
-    ci->bti_ist_info = 0;
+    ci->spec_ctrl_flags &= ~SCF_ist_wrmsr;
 
     ACPI_FLUSH_CPU_CACHE();
 
@@ -259,7 +259,7 @@ static int enter_state(u32 state)
         panic("Missing previously available feature(s).");
 
     /* Re-enabled default NMI/#MC use of MSR_SPEC_CTRL. */
-    ci->bti_ist_info = default_bti_ist_info;
+    ci->spec_ctrl_flags |= (default_spec_ctrl_flags & SCF_ist_wrmsr);
     spec_ctrl_exit_idle(ci);
 
  done:
diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c
index 6633c64..1ad3ff5 100644
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -39,7 +39,7 @@ static bool __initdata opt_rsb_native = true;
 static bool __initdata opt_rsb_vmexit = true;
 bool __read_mostly opt_ibpb = true;
 uint8_t __read_mostly default_xen_spec_ctrl;
-uint8_t __read_mostly default_bti_ist_info;
+uint8_t __read_mostly default_spec_ctrl_flags;
 
 static int __init parse_bti(const char *s)
 {
@@ -374,7 +374,7 @@ void __init init_speculation_mitigations(void)
         else
             setup_force_cpu_cap(X86_FEATURE_XEN_IBRS_CLEAR);
 
-        default_bti_ist_info |= BTI_IST_WRMSR;
+        default_spec_ctrl_flags |= SCF_ist_wrmsr;
     }
 
     /*
@@ -393,7 +393,7 @@ void __init init_speculation_mitigations(void)
     if ( opt_rsb_native )
     {
         setup_force_cpu_cap(X86_FEATURE_RSB_NATIVE);
-        default_bti_ist_info |= BTI_IST_RSB;
+        default_spec_ctrl_flags |= SCF_ist_rsb;
     }
 
     /*
@@ -407,7 +407,7 @@ void __init init_speculation_mitigations(void)
     if ( !boot_cpu_has(X86_FEATURE_IBRSB) && !boot_cpu_has(X86_FEATURE_IBPB) )
         opt_ibpb = false;
 
-    /* (Re)init BSP state now that default_bti_ist_info has been calculated. */
+    /* (Re)init BSP state now that default_spec_ctrl_flags has been calculated. */
     init_shadow_spec_ctrl_state();
 
     xpti_init_default(false);
@@ -421,6 +421,8 @@ void __init init_speculation_mitigations(void)
 
 static void __init __maybe_unused build_assertions(void)
 {
+    /* The optimised assembly relies on this alias. */
+    BUILD_BUG_ON(SCF_use_shadow != 1);
 }
 
 /*
diff --git a/xen/arch/x86/x86_64/asm-offsets.c b/xen/arch/x86/x86_64/asm-offsets.c
index f80d3b7..5957c76 100644
--- a/xen/arch/x86/x86_64/asm-offsets.c
+++ b/xen/arch/x86/x86_64/asm-offsets.c
@@ -135,8 +135,7 @@ void __dummy__(void)
     OFFSET(CPUINFO_pv_cr3, struct cpu_info, pv_cr3);
     OFFSET(CPUINFO_shadow_spec_ctrl, struct cpu_info, shadow_spec_ctrl);
     OFFSET(CPUINFO_xen_spec_ctrl, struct cpu_info, xen_spec_ctrl);
-    OFFSET(CPUINFO_use_shadow_spec_ctrl, struct cpu_info, use_shadow_spec_ctrl);
-    OFFSET(CPUINFO_bti_ist_info, struct cpu_info, bti_ist_info);
+    OFFSET(CPUINFO_spec_ctrl_flags, struct cpu_info, spec_ctrl_flags);
     OFFSET(CPUINFO_root_pgt_changed, struct cpu_info, root_pgt_changed);
     OFFSET(CPUINFO_use_pv_cr3, struct cpu_info, use_pv_cr3);
     DEFINE(CPUINFO_sizeof, sizeof(struct cpu_info));
diff --git a/xen/include/asm-x86/current.h b/xen/include/asm-x86/current.h
index 200e935..5bd64b2 100644
--- a/xen/include/asm-x86/current.h
+++ b/xen/include/asm-x86/current.h
@@ -55,8 +55,7 @@ struct cpu_info {
     /* See asm-x86/spec_ctrl_asm.h for usage. */
     unsigned int shadow_spec_ctrl;
     uint8_t      xen_spec_ctrl;
-    bool         use_shadow_spec_ctrl;
-    uint8_t      bti_ist_info;
+    uint8_t      spec_ctrl_flags;
 
     /*
      * The following field controls copying of the L4 page table of 64-bit
diff --git a/xen/include/asm-x86/spec_ctrl.h b/xen/include/asm-x86/spec_ctrl.h
index 0c7663a..d5bd4df 100644
--- a/xen/include/asm-x86/spec_ctrl.h
+++ b/xen/include/asm-x86/spec_ctrl.h
@@ -28,7 +28,7 @@ void init_speculation_mitigations(void);
 
 extern bool opt_ibpb;
 extern uint8_t default_xen_spec_ctrl;
-extern uint8_t default_bti_ist_info;
+extern uint8_t default_spec_ctrl_flags;
 
 extern uint8_t opt_xpti;
 #define OPT_XPTI_DOM0  0x01
@@ -38,9 +38,9 @@ static inline void init_shadow_spec_ctrl_state(void)
 {
     struct cpu_info *info = get_cpu_info();
 
-    info->shadow_spec_ctrl = info->use_shadow_spec_ctrl = 0;
+    info->shadow_spec_ctrl = 0;
     info->xen_spec_ctrl = default_xen_spec_ctrl;
-    info->bti_ist_info = default_bti_ist_info;
+    info->spec_ctrl_flags = default_spec_ctrl_flags;
 }
 
 /* WARNING! `ret`, `call *`, `jmp *` not safe after this call. */
@@ -54,7 +54,7 @@ static always_inline void spec_ctrl_enter_idle(struct cpu_info *info)
      */
     info->shadow_spec_ctrl = val;
     barrier();
-    info->use_shadow_spec_ctrl = true;
+    info->spec_ctrl_flags |= SCF_use_shadow;
     barrier();
     asm volatile ( ALTERNATIVE(ASM_NOP3, "wrmsr", X86_FEATURE_XEN_IBRS_SET)
                    :: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0) : "memory" );
@@ -69,7 +69,7 @@ static always_inline void spec_ctrl_exit_idle(struct cpu_info *info)
      * Disable shadowing before updating the MSR.  There are no SMP issues
      * here; only local processor ordering concerns.
      */
-    info->use_shadow_spec_ctrl = false;
+    info->spec_ctrl_flags &= ~SCF_use_shadow;
     barrier();
     asm volatile ( ALTERNATIVE(ASM_NOP3, "wrmsr", X86_FEATURE_XEN_IBRS_SET)
                    :: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0) : "memory" );
diff --git a/xen/include/asm-x86/spec_ctrl_asm.h b/xen/include/asm-x86/spec_ctrl_asm.h
index e8e8f9a..97da08b 100644
--- a/xen/include/asm-x86/spec_ctrl_asm.h
+++ b/xen/include/asm-x86/spec_ctrl_asm.h
@@ -20,9 +20,10 @@
 #ifndef __X86_SPEC_CTRL_ASM_H__
 #define __X86_SPEC_CTRL_ASM_H__
 
-/* Encoding of the bottom bits in cpuinfo.bti_ist_info */
-#define BTI_IST_WRMSR (1 << 1)
-#define BTI_IST_RSB   (1 << 2)
+/* Encoding of cpuinfo.spec_ctrl_flags */
+#define SCF_use_shadow (1 << 0)
+#define SCF_ist_wrmsr  (1 << 1)
+#define SCF_ist_rsb    (1 << 2)
 
 #ifdef __ASSEMBLY__
 #include <asm/msr-index.h>
@@ -49,20 +50,20 @@
  * after VMEXIT.  The VMEXIT-specific code reads MSR_SPEC_CTRL and updates
  * current before loading Xen's MSR_SPEC_CTRL setting.
  *
- * Factor 2 is harder.  We maintain a shadow_spec_ctrl value, and
- * use_shadow_spec_ctrl boolean per cpu.  The synchronous use is:
+ * Factor 2 is harder.  We maintain a shadow_spec_ctrl value, and a use_shadow
+ * boolean in the per cpu spec_ctrl_flags.  The synchronous use is:
  *
  *  1) Store guest value in shadow_spec_ctrl
- *  2) Set use_shadow_spec_ctrl boolean
+ *  2) Set the use_shadow boolean
  *  3) Load guest value into MSR_SPEC_CTRL
  *  4) Exit to guest
  *  5) Entry from guest
- *  6) Clear use_shadow_spec_ctrl boolean
+ *  6) Clear the use_shadow boolean
  *  7) Load Xen's value into MSR_SPEC_CTRL
  *
  * The asynchronous use for interrupts/exceptions is:
  *  -  Set/clear IBRS on entry to Xen
- *  -  On exit to Xen, check use_shadow_spec_ctrl
+ *  -  On exit to Xen, check use_shadow
  *  -  If set, load shadow_spec_ctrl
  *
  * Therefore, an interrupt/exception which hits the synchronous path between
@@ -134,7 +135,7 @@
     xor %edx, %edx
 
     /* Clear SPEC_CTRL shadowing *before* loading Xen's value. */
-    movb %dl, CPUINFO_use_shadow_spec_ctrl(%rsp)
+    andb $~SCF_use_shadow, CPUINFO_spec_ctrl_flags(%rsp)
 
     /* Load Xen's intended value. */
     mov $\ibrs_val, %eax
@@ -160,12 +161,14 @@
      * block so calculate the position directly.
      */
     .if \maybexen
+        xor %eax, %eax
         /* Branchless `if ( !xen ) clear_shadowing` */
         testb $3, UREGS_cs(%rsp)
-        setz %al
-        and %al, STACK_CPUINFO_FIELD(use_shadow_spec_ctrl)(%r14)
+        setnz %al
+        not %eax
+        and %al, STACK_CPUINFO_FIELD(spec_ctrl_flags)(%r14)
     .else
-        movb %dl, CPUINFO_use_shadow_spec_ctrl(%rsp)
+        andb $~SCF_use_shadow, CPUINFO_spec_ctrl_flags(%rsp)
     .endif
 
     /* Load Xen's intended value. */
@@ -184,8 +187,8 @@
  */
     xor %edx, %edx
 
-    cmpb %dl, STACK_CPUINFO_FIELD(use_shadow_spec_ctrl)(%rbx)
-    je .L\@_skip
+    testb $SCF_use_shadow, STACK_CPUINFO_FIELD(spec_ctrl_flags)(%rbx)
+    jz .L\@_skip
 
     mov STACK_CPUINFO_FIELD(shadow_spec_ctrl)(%rbx), %eax
     mov $MSR_SPEC_CTRL, %ecx
@@ -206,7 +209,7 @@
     mov %eax, CPUINFO_shadow_spec_ctrl(%rsp)
 
     /* Set SPEC_CTRL shadowing *before* loading the guest value. */
-    movb $1, CPUINFO_use_shadow_spec_ctrl(%rsp)
+    orb $SCF_use_shadow, CPUINFO_spec_ctrl_flags(%rsp)
 
     mov $MSR_SPEC_CTRL, %ecx
     xor %edx, %edx
@@ -265,22 +268,23 @@
  * This is logical merge of DO_OVERWRITE_RSB and DO_SPEC_CTRL_ENTRY
  * maybexen=1, but with conditionals rather than alternatives.
  */
-    movzbl STACK_CPUINFO_FIELD(bti_ist_info)(%r14), %eax
+    movzbl STACK_CPUINFO_FIELD(spec_ctrl_flags)(%r14), %eax
 
-    testb $BTI_IST_RSB, %al
+    test $SCF_ist_rsb, %al
     jz .L\@_skip_rsb
 
     DO_OVERWRITE_RSB tmp=rdx /* Clobbers %rcx/%rdx */
 
 .L\@_skip_rsb:
 
-    testb $BTI_IST_WRMSR, %al
+    test $SCF_ist_wrmsr, %al
     jz .L\@_skip_wrmsr
 
     xor %edx, %edx
     testb $3, UREGS_cs(%rsp)
-    setz %dl
-    and %dl, STACK_CPUINFO_FIELD(use_shadow_spec_ctrl)(%r14)
+    setnz %dl
+    not %edx
+    and %dl, STACK_CPUINFO_FIELD(spec_ctrl_flags)(%r14)
 
     /* Load Xen's intended value. */
     mov $MSR_SPEC_CTRL, %ecx
@@ -307,7 +311,7 @@ UNLIKELY_DISPATCH_LABEL(\@_serialise):
  * Requires %rbx=stack_end
  * Clobbers %rax, %rcx, %rdx
  */
-    testb $BTI_IST_WRMSR, STACK_CPUINFO_FIELD(bti_ist_info)(%rbx)
+    testb $SCF_ist_wrmsr, STACK_CPUINFO_FIELD(spec_ctrl_flags)(%rbx)
     jz .L\@_skip
 
     DO_SPEC_CTRL_EXIT_TO_XEN
-- 
2.1.4


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