Fields that generic_identify() sets unconditionally don't need pre-
setting. (In fact the compiler removes some of those assignments anyway,
at least in release builds.)

With the setting of ->cpuid_level to -1 gone, also drop the respective
BUG_ON() from default_init().

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

--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -114,8 +114,6 @@ bool __init is_forced_cpu_cap(unsigned i
 static void cf_check default_init(struct cpuinfo_x86 * c)
 {
 	/* Not much we can do here... */
-	/* Check if at least it has cpuid */
-	BUG_ON(c->cpuid_level == -1);
 	__clear_bit(X86_FEATURE_SEP, c->x86_capability);
 }
 
@@ -492,15 +490,11 @@ void identify_cpu(struct cpuinfo_x86 *c)
 	int i;
 
 	c->x86_cache_size = -1;
-	c->x86_vendor = X86_VENDOR_UNKNOWN;
-	c->cpuid_level = -1;	/* CPUID not detected */
 	c->x86_model = c->x86_mask = 0;	/* So far unknown... */
-	c->x86_vendor_id[0] = '\0'; /* Unset */
 	c->x86_model_id[0] = '\0';  /* Unset */
 	c->x86_max_cores = 1;
 	c->x86_num_siblings = 1;
 	c->x86_clflush_size = 0;
-	c->phys_proc_id = XEN_INVALID_SOCKET_ID;
 	c->cpu_core_id = XEN_INVALID_CORE_ID;
 	c->compute_unit_id = INVALID_CUID;
 	memset(&c->x86_capability, 0, sizeof c->x86_capability);

On 13/06/2023 7:12 am, Jan Beulich wrote:
> Fields that generic_identify() sets unconditionally don't need pre-
> setting. (In fact the compiler removes some of those assignments anyway,
> at least in release builds.)
>
> With the setting of ->cpuid_level to -1 gone, also drop the respective
> BUG_ON() from default_init().
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

I have some far more extensive plans in this, but no work started yet.