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[PATCH] x86/cpuid: Fix HLE and RTM handling (again)

  • To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Mon, 7 Jun 2021 13:41:16 +0100
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  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
  • Delivery-date: Mon, 07 Jun 2021 12:41:43 +0000
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For reasons which are my fault, but I don't recall why, the
FDP_EXCP_ONLY/NO_FPU_SEL adjustment uses the whole special_features[] array,
not the two relevant bits.

HLE and RTM were recently added to the list of special features, causing them
to be always set in guest view, irrespective of the toolstacks choice on the

Rewrite the logic to refer to the features specifically, rather than relying
on the contents of the special_features[] array.

Fixes: 8fe24090d9 ("x86/cpuid: Rework HLE and RTM handling")
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reported-by: Edwin Török <edvin.torok@xxxxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
 xen/arch/x86/cpuid.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index f3c8950aa3..958caf35da 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -672,9 +672,11 @@ void recalculate_cpuid_policy(struct domain *d)
     /* Fold host's FDP_EXCP_ONLY and NO_FPU_SEL into guest's view. */
-    fs[FEATURESET_7b0] &= ~special_features[FEATURESET_7b0];
+    fs[FEATURESET_7b0] &= ~(cpufeat_mask(X86_FEATURE_FDP_EXCP_ONLY) |
+                            cpufeat_mask(X86_FEATURE_NO_FPU_SEL));
     fs[FEATURESET_7b0] |= (host_cpuid_policy.feat._7b0 &
-                           special_features[FEATURESET_7b0]);
+                           (cpufeat_mask(X86_FEATURE_FDP_EXCP_ONLY) |
+                            cpufeat_mask(X86_FEATURE_NO_FPU_SEL)));
     cpuid_featureset_to_policy(fs, p);



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