[xen staging] x86/cpuid: Clobber CPUID leaves 0x800000{1d..20} in policies

[patchbot@xxxxxxx]

commit d4012d50082c2eae2f3cbe7770be13b9227fbc3f
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Apr 6 22:40:20 2022 +0100
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Thu Apr 7 11:36:45 2022 +0100

    x86/cpuid: Clobber CPUID leaves 0x800000{1d..20} in policies
    
    c/s 1a914256dca5 increased the AMD max leaf from 0x8000001c to 0x80000021, 
but
    did not adjust anything in the calculate_*_policy() chain.  As a result, on
    hardware supporting these leaves, we read the real hardware values into the
    raw policy, then copy into host, and all the way into the PV/HVM default
    policies.
    
    All 4 of these leaves have enable bits (first two by TopoExt, next by SEV,
    next by PQOS), so any software following the rules is fine and will leave 
them
    alone.  However, leaf 0x8000001d takes a subleaf input and at least two
    userspace utilities have been observed to loop indefinitely under Xen 
(clearly
    waiting for eax to report "no more cache levels").
    
    Such userspace is buggy, but Xen's behaviour isn't great either.
    
    In the short term, clobber all information in these leaves.  This is a giant
    bodge, but there are complexities with implementing all of these leaves
    properly.
    
    Fixes: 1a914256dca5 ("x86/cpuid: support LFENCE always serialising CPUID 
bit")
    Link: https://github.com/QubesOS/qubes-issues/issues/7392
    Reported-by: fosslinux <fosslinux@aussies.space>
    Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/cpuid.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index bb554b06a7..7e0b395698 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -328,8 +328,15 @@ static void recalculate_misc(struct cpuid_policy *p)
 
         zero_leaves(p->extd.raw, 0xb, 0x18);
 
+        /* 0x19 - TLB details.  Pass through. */
+        /* 0x1a - Perf hints.   Pass through. */
+
         p->extd.raw[0x1b] = EMPTY_LEAF; /* IBS - not supported. */
         p->extd.raw[0x1c] = EMPTY_LEAF; /* LWP - not supported. */
+        p->extd.raw[0x1d] = EMPTY_LEAF; /* TopoExt Cache */
+        p->extd.raw[0x1e] = EMPTY_LEAF; /* TopoExt APIC ID/Core/Node */
+        p->extd.raw[0x1f] = EMPTY_LEAF; /* SEV */
+        p->extd.raw[0x20] = EMPTY_LEAF; /* Platform QoS */
         break;
     }
 }
--
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