We are about to move MSR_ARCH_CAPS into featureset, but the order of
operations (copy raw policy, then copy x86_capabilitiles[] in) will end up
clobbering the ARCH_CAPS value currently visible in the Host policy.

To avoid this transient breakage, read from raw_cpu_policy rather than
modifying it in place.  This logic will be removed entirely in due course.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>
---
 xen/arch/x86/cpu-policy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/cpu-policy.c b/xen/arch/x86/cpu-policy.c
index 5e7e19fbcda8..49f5465ec445 100644
--- a/xen/arch/x86/cpu-policy.c
+++ b/xen/arch/x86/cpu-policy.c
@@ -411,7 +411,7 @@ static void __init calculate_host_policy(void)
     p->platform_info.cpuid_faulting = cpu_has_cpuid_faulting;
 
     /* Temporary, until we have known_features[] for feature bits in MSRs. */
-    p->arch_caps.raw &=
+    p->arch_caps.raw = raw_cpu_policy.arch_caps.raw &
         (ARCH_CAPS_RDCL_NO | ARCH_CAPS_IBRS_ALL | ARCH_CAPS_RSBA |
          ARCH_CAPS_SKIP_L1DFL | ARCH_CAPS_SSB_NO | ARCH_CAPS_MDS_NO |
          ARCH_CAPS_IF_PSCHANGE_MC_NO | ARCH_CAPS_TSX_CTRL | ARCH_CAPS_TAA_NO |
-- 
2.30.2

On 15.05.2023 16:42, Andrew Cooper wrote:
> We are about to move MSR_ARCH_CAPS into featureset, but the order of
> operations (copy raw policy, then copy x86_capabilitiles[] in) will end up
> clobbering the ARCH_CAPS value currently visible in the Host policy.
> 
> To avoid this transient breakage, read from raw_cpu_policy rather than
> modifying it in place.  This logic will be removed entirely in due course.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Acked-by: Jan Beulich <jbeulich@suse.com>