[xen stable-4.16] x86/cpuid: Split dom0 handling out of init_domain_cpuid_policy()

[patchbot@xxxxxxx]

commit 4d0dc655aa7135c44ab99641d95a3d32bdf3c09d
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Wed Dec 15 15:36:59 2021 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Aug 8 16:02:53 2023 +0100

    x86/cpuid: Split dom0 handling out of init_domain_cpuid_policy()
    
    To implement dom0-cpuid= support, the special cases would need extending.
    However there is already a problem with late hwdom where the special cases
    override toolstack settings, which is unintended and poor behaviour.
    
    Introduce a new init_dom0_cpuid_policy() for the purpose, moving the ITSC 
and
    ARCH_CAPS logic.  The is_hardware_domain() can be dropped, and for now there
    is no need to rerun recalculate_cpuid_policy(); this is a relatively 
expensive
    operation, and will become more-so over time.
    
    Rearrange the logic in create_dom0() to make room for a call to
    init_dom0_cpuid_policy().  The AMX plans for having variable sized XSAVE
    states require that modifications to the policy happen before vCPUs are
    created.
    
    Additionally, factor out domid into a variable so we can be slightly more
    correct in the case of a failure, and also print the error from
    domain_create().  This will at least help distinguish -EINVAL from -ENOMEM.
    
    No practical change in behaviour.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    (cherry picked from commit c17072fc164a72583fda8e2b836c71d2e3f8e84d)
---
 xen/arch/x86/cpuid.c        | 25 +++++++++++++++----------
 xen/arch/x86/setup.c        | 15 +++++++++++----
 xen/include/asm-x86/cpuid.h |  3 +++
 3 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index a647331f47..0693543ea0 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -742,23 +742,28 @@ int init_domain_cpuid_policy(struct domain *d)
     if ( !p )
         return -ENOMEM;
 
-    /* The hardware domain can't migrate.  Give it ITSC if available. */
-    if ( is_hardware_domain(d) )
-        p->extd.itsc = cpu_has_itsc;
+    d->arch.cpuid = p;
+
+    recalculate_cpuid_policy(d);
+
+    return 0;
+}
+
+void __init init_dom0_cpuid_policy(struct domain *d)
+{
+    struct cpuid_policy *p = d->arch.cpuid;
+
+    /* dom0 can't migrate.  Give it ITSC if available. */
+    if ( cpu_has_itsc )
+        p->extd.itsc = true;
 
     /*
      * Expose the "hardware speculation behaviour" bits of ARCH_CAPS to dom0,
      * so dom0 can turn off workarounds as appropriate.  Temporary, until the
      * domain policy logic gains a better understanding of MSRs.
      */
-    if ( is_hardware_domain(d) && cpu_has_arch_caps )
+    if ( cpu_has_arch_caps )
         p->feat.arch_caps = true;
-
-    d->arch.cpuid = p;
-
-    recalculate_cpuid_policy(d);
-
-    return 0;
 }
 
 void guest_cpuid(const struct vcpu *v, uint32_t leaf,
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index f0de805780..d2df3047f3 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -787,6 +787,7 @@ static struct domain *__init create_dom0(const module_t 
*image,
     };
     struct domain *d;
     char *cmdline;
+    domid_t domid;
 
     if ( opt_dom0_pvh )
     {
@@ -801,10 +802,16 @@ static struct domain *__init create_dom0(const module_t 
*image,
     if ( iommu_enabled )
         dom0_cfg.flags |= XEN_DOMCTL_CDF_iommu;
 
-    /* Create initial domain 0. */
-    d = domain_create(get_initial_domain_id(), &dom0_cfg, !pv_shim);
-    if ( IS_ERR(d) || (alloc_dom0_vcpu0(d) == NULL) )
-        panic("Error creating domain 0\n");
+    /* Create initial domain.  Not d0 for pvshim. */
+    domid = get_initial_domain_id();
+    d = domain_create(domid, &dom0_cfg, !pv_shim);
+    if ( IS_ERR(d) )
+        panic("Error creating d%u: %ld\n", domid, PTR_ERR(d));
+
+    init_dom0_cpuid_policy(d);
+
+    if ( alloc_dom0_vcpu0(d) == NULL )
+        panic("Error creating d%uv0\n", domid);
 
     /* Grab the DOM0 command line. */
     cmdline = image->string ? __va(image->string) : NULL;
diff --git a/xen/include/asm-x86/cpuid.h b/xen/include/asm-x86/cpuid.h
index 46904061d0..9c3637549a 100644
--- a/xen/include/asm-x86/cpuid.h
+++ b/xen/include/asm-x86/cpuid.h
@@ -59,6 +59,9 @@ bool recheck_cpu_features(unsigned int cpu);
 /* Allocate and initialise a CPUID policy suitable for the domain. */
 int init_domain_cpuid_policy(struct domain *d);
 
+/* Apply dom0-specific tweaks to the CPUID policy. */
+void init_dom0_cpuid_policy(struct domain *d);
+
 /* Clamp the CPUID policy to reality. */
 void recalculate_cpuid_policy(struct domain *d);
 
--
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