[xen staging-4.18] x86/ucode: Fix stability of the raw CPU Policy rescan

[patchbot@xxxxxxx]

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commit b1fdd7d0e47e0831ac7a99d0417385fc10d3068c
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Thu Feb 1 18:02:24 2024 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Feb 1 18:02:24 2024 +0100

    x86/ucode: Fix stability of the raw CPU Policy rescan
    
    Always run microcode_update_helper() on the BSP, so the the updated Raw CPU
    policy doesn't get non-BSP topology details included.
    
    Have calculate_raw_cpu_policy() clear the instantanious XSTATE sizes.  The
    value XCR0 | MSR_XSS had when we scanned the policy isn't terribly 
interesting
    to report.
    
    When CPUID Masking is active, it affects CPUID instructions issued by Xen
    too.  Transiently disable masking to get a clean scan.
    
    Fixes: 694d79ed5aac ("x86/ucode: Refresh raw CPU policy after microcode 
load")
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: cf7fe8b72deaa94157ddf97d4bb391480205e9c2
    master date: 2024-01-25 17:46:57 +0000
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