[xen staging] x86/spec-ctrl: Fix default calculation of opt_srb_lock

[patchbot@xxxxxxx]

commit 31f3bc97f4508687215e459a5e35676eecf1772b
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Jan 4 14:11:55 2022 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Jan 5 09:44:26 2022 +0000

    x86/spec-ctrl: Fix default calculation of opt_srb_lock
    
    Since this logic was introduced, opt_tsx has become more complicated and
    shouldn't be compared to 0 directly.  While there are no buggy logic paths,
    the correct expression is !(opt_tsx & 1) but the rtm_disabled boolean is
    easier and clearer to use.
    
    Fixes: 8fe24090d940 ("x86/cpuid: Rework HLE and RTM handling")
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/spec_ctrl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c
index a5569c7f2b..c18cc8aa49 100644
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -1245,7 +1245,7 @@ void __init init_speculation_mitigations(void)
          */
         if ( opt_srb_lock == -1 &&
              (caps & (ARCH_CAPS_MDS_NO|ARCH_CAPS_TAA_NO)) == ARCH_CAPS_MDS_NO 
&&
-             (!cpu_has_hle || ((caps & ARCH_CAPS_TSX_CTRL) && opt_tsx == 0)) )
+             (!cpu_has_hle || ((caps & ARCH_CAPS_TSX_CTRL) && rtm_disabled)) )
             opt_srb_lock = 0;
 
         val &= ~MCU_OPT_CTRL_RNGDS_MITG_DIS;
--
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