File 5cdad090-x86-spec-ctrl-misc-non-functional-clea... of Package xen

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File 5cdad090-x86-spec-ctrl-misc-non-functional-cleanup.patch of Package xen (Revision 7cefad5edb09a35359b01695ee5db5fa)

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# Commit 9b62eba6c429c327e1507816bef403ccc87357ae
# Date 2019-05-14 15:28:32 +0100
# Author Andrew Cooper <andrew.cooper3@citrix.com>
# Committer Andrew Cooper <andrew.cooper3@citrix.com>
x86/spec-ctrl: Misc non-functional cleanup

* Identify BTI in the spec_ctrl_{enter,exit}_idle() comments, as other
   mitigations will shortly appear.
 * Use alternative_input() and cover the lack of memory cobber with a further
   barrier.

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

--- a/xen/include/asm-x86/spec_ctrl.h
+++ b/xen/include/asm-x86/spec_ctrl.h
@@ -68,6 +68,8 @@ static always_inline void spec_ctrl_ente
     uint32_t val = 0;
 
     /*
+     * Branch Target Injection:
+     *
      * Latch the new shadow value, then enable shadowing, then update the MSR.
      * There are no SMP issues here; only local processor ordering concerns.
      */
@@ -75,8 +77,9 @@ static always_inline void spec_ctrl_ente
     barrier();
     info->spec_ctrl_flags |= SCF_use_shadow;
     barrier();
-    asm volatile ( ALTERNATIVE("", "wrmsr", X86_FEATURE_SC_MSR_IDLE)
-                   :: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0) : "memory" );
+    alternative_input("", "wrmsr", X86_FEATURE_SC_MSR_IDLE,
+                      "a" (val), "c" (MSR_SPEC_CTRL), "d" (0));
+    barrier();
 }
 
 /* WARNING! `ret`, `call *`, `jmp *` not safe before this call. */
@@ -85,13 +88,16 @@ static always_inline void spec_ctrl_exit
     uint32_t val = info->xen_spec_ctrl;
 
     /*
+     * Branch Target Injection:
+     *
      * Disable shadowing before updating the MSR.  There are no SMP issues
      * here; only local processor ordering concerns.
      */
     info->spec_ctrl_flags &= ~SCF_use_shadow;
     barrier();
-    asm volatile ( ALTERNATIVE("", "wrmsr", X86_FEATURE_SC_MSR_IDLE)
-                   :: "a" (val), "c" (MSR_SPEC_CTRL), "d" (0) : "memory" );
+    alternative_input("", "wrmsr", X86_FEATURE_SC_MSR_IDLE,
+                      "a" (val), "c" (MSR_SPEC_CTRL), "d" (0));
+    barrier();
 }
 
 #endif /* __ASSEMBLY__ */

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File 5cdad090-x86-spec-ctrl-misc-non-functional-cleanup.patch of Package xen (Revision 7cefad5edb09a35359b01695ee5db5fa)

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