[SRU][mantic:linux-gcp/aws, lunar:linux-gcp/aws][PATCH 1/1] x86/boot: Move x86_cache_alignment initialization to correct spot

[John Cabaj]

From: Dave Hansen <dave.hansen at linux.intel.com>

BugLink: https://bugs.launchpad.net/bugs/2039191

c->x86_cache_alignment is initialized from c->x86_clflush_size.
However, commit fbf6449f84bf moved c->x86_clflush_size initialization
to later in boot without moving the c->x86_cache_alignment assignment:

  fbf6449f84bf ("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: fbf6449f84bf ("x86/sev-es: Set x86_virt_bits to the correct value straight away, instead of a two-phase approach")
Signed-off-by: Dave Hansen <dave.hansen at linux.intel.com>
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Tested-by: Nathan Chancellor <nathan at kernel.org>
Link: https://lore.kernel.org/r/20231002220045.1014760-1-dave.hansen@linux.intel.com
(cherry picked from commit 3e32552652917f10c0aa8ac75cdc8f0b8d257dec linux-next)
Signed-off-by: John Cabaj <john.cabaj at canonical.com>
---
 arch/x86/kernel/cpu/common.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 6933297b9949..727a82600c82 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1126,6 +1126,7 @@ 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)
@@ -1576,8 +1577,6 @@ 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;
 
-- 
2.34.1