[xen stable-4.15] x86/spec-ctrl: Fix default calculation of opt_srb_lock

[patchbot@xxxxxxx]

commit a763f8f158e81158bdf2470dbc3d98353f2322e2
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Jan 7 08:16:03 2022 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jan 7 08:16:03 2022 +0100

    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>
    master commit: 31f3bc97f4508687215e459a5e35676eecf1772b
    master date: 2022-01-05 09:44:26 +0000
---
 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 7e0c171dc8..f70535b6e7 100644
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -1197,7 +1197,7 @@ 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;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.15