[PATCH 3/3] x86/ucode: Remove the collect_cpu_info() call from parse_blob()

[Andrew Cooper <andrew.cooper3@citrix.com>]

With the tangle of logic starting to come under control, it is now plain to
see that parse_blob()'s side effect of re-gathering the signature/revision is
pointless.

The cpu_request_microcode() hooks need the signature only.  The BSP gathers
this in early_microcode_init(), the APs and S3 in microcode_update_cpu().  For
good measure, the apply_microcode() hooks also keep the revision correct as
load attempts are made.

This finally gets us down to a single call per CPU on boot / S3 resume, and no
calls during late-load hypercalls.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>

Slightly RFC.

Just before posting, I've realised that cpu_request_microcode() does actually
use the current CPU revision, and it's buggy, and it's the cause of `xen-ucode
--force` not working as expected.

I'm tempted to do another series cleaning that up in isolation, such that this
patch becomes true in this form.

---
 xen/arch/x86/cpu/microcode/core.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/xen/arch/x86/cpu/microcode/core.c b/xen/arch/x86/cpu/microcode/core.c
index fd4b08b45388..5897ec54032a 100644
--- a/xen/arch/x86/cpu/microcode/core.c
+++ b/xen/arch/x86/cpu/microcode/core.c
@@ -189,8 +189,6 @@ static struct patch_with_flags nmi_patch =
  */
 static struct microcode_patch *parse_blob(const char *buf, size_t len)
 {
-    alternative_vcall(ucode_ops.collect_cpu_info);
-
     return alternative_call(ucode_ops.cpu_request_microcode, buf, len, true);
 }
 
-- 
2.39.5