[xen stable-4.16] x86/cpu-policy: Rearrange guest_common_default_feature_adjustments()

[patchbot@xxxxxxx]

commit d80d4cc42fac8969766b0ad9124fef3719dd2939
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Mar 10 16:23:20 2023 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Aug 8 16:02:54 2023 +0100

    x86/cpu-policy: Rearrange guest_common_default_feature_adjustments()
    
    This is prep work, split out to simply the diff on the following change.
    
     * Split the INTEL check out of the IvyBridge RDRAND check, as the former 
will
       be reused.
    
    No functional change.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    (cherry picked from commit 064f572f96f1558faae0a74cad616ba95ec8ff34)
---
 xen/arch/x86/cpu-policy.c | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/cpu-policy.c b/xen/arch/x86/cpu-policy.c
index 770742a78e..f78baa2059 100644
--- a/xen/arch/x86/cpu-policy.c
+++ b/xen/arch/x86/cpu-policy.c
@@ -429,21 +429,24 @@ static void __init 
guest_common_max_feature_adjustments(uint32_t *fs)
 
 static void __init guest_common_default_feature_adjustments(uint32_t *fs)
 {
-    /*
-     * IvyBridge client parts suffer from leakage of RDRAND data due to SRBDS
-     * (XSA-320 / CVE-2020-0543), and won't be receiving microcode to
-     * compensate.
-     *
-     * Mitigate by hiding RDRAND from guests by default, unless explicitly
-     * overridden on the Xen command line (cpuid=rdrand).  Irrespective of the
-     * default setting, guests can use RDRAND if explicitly enabled
-     * (cpuid="host,rdrand=1") in the VM's config file, and VMs which were
-     * previously using RDRAND can migrate in.
-     */
-    if ( boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
-         boot_cpu_data.x86 == 6 && boot_cpu_data.x86_model == 0x3a &&
-         cpu_has_rdrand && !is_forced_cpu_cap(X86_FEATURE_RDRAND) )
-        __clear_bit(X86_FEATURE_RDRAND, fs);
+    if ( boot_cpu_data.x86_vendor == X86_VENDOR_INTEL )
+    {
+        /*
+         * IvyBridge client parts suffer from leakage of RDRAND data due to 
SRBDS
+         * (XSA-320 / CVE-2020-0543), and won't be receiving microcode to
+         * compensate.
+         *
+         * Mitigate by hiding RDRAND from guests by default, unless explicitly
+         * overridden on the Xen command line (cpuid=rdrand).  Irrespective of 
the
+         * default setting, guests can use RDRAND if explicitly enabled
+         * (cpuid="host,rdrand=1") in the VM's config file, and VMs which were
+         * previously using RDRAND can migrate in.
+         */
+        if ( boot_cpu_data.x86 == 6 &&
+             boot_cpu_data.x86_model == 0x3a /* INTEL_FAM6_IVYBRIDGE */ &&
+             cpu_has_rdrand && !is_forced_cpu_cap(X86_FEATURE_RDRAND) )
+            __clear_bit(X86_FEATURE_RDRAND, fs);
+    }
 
     /*
      * On certain hardware, speculative or errata workarounds can result in
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.16