x86/boot: Move x86_cache_alignment initialization to correct spot

c->x86_cache_alignment is initialized from c->x86_clflush_size.
However, commit fbf6449 moved c->x86_clflush_size initialization
to later in boot without moving the c->x86_cache_alignment assignment:

  fbf6449 ("x86/sev-es: Set x86_virt_bits to the correct value straight away, instead of a two-phase approach")

This presumably left c->x86_cache_alignment set to zero for longer
than it should be.

The result was an oops on 32-bit kernels while accessing a pointer
at 0x20.  The 0x20 came from accessing a structure member at offset
0x10 (buffer->cpumask) from a ZERO_SIZE_PTR=0x10.  kmalloc() can
evidently return ZERO_SIZE_PTR when it's given 0 as its alignment
requirement.

Move the c->x86_cache_alignment initialization to be after
c->x86_clflush_size has an actual value.

Fixes: fbf6449 ("x86/sev-es: Set x86_virt_bits to the correct value straight away, instead of a two-phase approach")
Signed-off-by: Dave Hansen <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: hansendc

arch/x86/kernel/cpu/common.c

@@ -1141,6 +1141,7 @@ void get_cpu_address_sizes(struct cpuinfo_x86 *c)
 		}
 	}
 	c->x86_cache_bits = c->x86_phys_bits;
+	c->x86_cache_alignment = c->x86_clflush_size;
 }
 
 static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
@@ -1594,8 +1595,6 @@ static void __init cpu_parse_early_param(void)
  */
 static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 {
-	c->x86_cache_alignment = c->x86_clflush_size;
-
 	memset(&c->x86_capability, 0, sizeof(c->x86_capability));
 	c->extended_cpuid_level = 0;