[PATCH v7 2/9] x86/resctrl: Require 64-bit x86 for resctrl support

[Chen Yu <yu.c.chen@intel.com>]

All known hardware that supports Intel RDT or AMD QoS is 64-bit. MMIO-based
Enhanced RDT (ERDT) monitoring requires readq()/writeq(), which are only
available on 64-bit.

32-bit x86 is maintained for legacy reasons. New CPU features are generally not
enabled for 32-bit systems, its test coverage keeps shrinking, and modern 32-bit
distributions have become rare. Discouraging the use of a 32-bit kernel is
discussed at:
https://lore.kernel.org/all/c6ab0c24-8931-4f0d-9be6-23498ab4c38b@intel.com/

Drop 32-bit support by changing the X86_CPU_RESCTRL dependency from X86 to
X86_64.

Since X86_CPU_RESCTRL now implies X86_64, remove the redundant X86_64 dependency
from X86_CPU_RESCTRL_INTEL_AET.

Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Tested-by: Hongyu Ning <hongyu.ning@linux.intel.com>
---
v6->v7:
    Replace the inaccurate "no realistic server use case" rationale with
    the legacy, shrinking test coverage and rare distro reasoning.
    (Reinette Chatre, Tony Luck, Dave Hansen, Borislav Petkov, Peter Zijlstra)
---
 arch/x86/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index bdad90f210e4..6685e120cff3 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -514,7 +514,7 @@ config X86_MPPARSE
 
 config X86_CPU_RESCTRL
 	bool "x86 CPU resource control support"
-	depends on X86 && (CPU_SUP_INTEL || CPU_SUP_AMD)
+	depends on X86_64 && (CPU_SUP_INTEL || CPU_SUP_AMD)
 	depends on MISC_FILESYSTEMS
 	select ARCH_HAS_CPU_RESCTRL
 	select RESCTRL_FS
@@ -537,7 +537,7 @@ config X86_CPU_RESCTRL
 
 config X86_CPU_RESCTRL_INTEL_AET
 	bool "Intel Application Energy Telemetry"
-	depends on X86_64 && X86_CPU_RESCTRL && CPU_SUP_INTEL && INTEL_PMT_TELEMETRY=y && INTEL_TPMI=y
+	depends on X86_CPU_RESCTRL && CPU_SUP_INTEL && INTEL_PMT_TELEMETRY=y && INTEL_TPMI=y
 	help
 	  Enable per-RMID telemetry events in resctrl.
 
-- 
2.25.1