x86,bugs: Unconditionally allow spectre_v2=retpoline,amd

Currently Linux prevents usage of retpoline,amd on !AMD hardware, this
is unfriendly and gets in the way of testing. Remove this restriction.

Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Borislav Petkov <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Tested-by: Alexei Starovoitov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: Peter Zijlstra

arch/x86/kernel/cpu/bugs.c

@@ -882,13 +882,6 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 		return SPECTRE_V2_CMD_AUTO;
 	}
 
-	if (cmd == SPECTRE_V2_CMD_RETPOLINE_AMD &&
-	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON &&
-	    boot_cpu_data.x86_vendor != X86_VENDOR_AMD) {
-		pr_err("retpoline,amd selected but CPU is not AMD. Switching to AUTO select\n");
-		return SPECTRE_V2_CMD_AUTO;
-	}
-
 	spec_v2_print_cond(mitigation_options[i].option,
 			   mitigation_options[i].secure);
 	return cmd;