Re: [PATCH v19 2/7] firmware: arm_rmm: Check for RMI support at init
From: Suzuki K Poulose
Date: Mon Sep 28 2026 - 04:10:44 EST
On 27/09/2026 10:29, Marc Zyngier wrote:
On Fri, 25 Sep 2026 16:23:49 +0100,
Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
On 25/09/2026 11:42, Catalin Marinas wrote:
On Thu, Sep 24, 2026 at 02:51:56PM +0100, Suzuki K Poulose wrote:
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 32102c3912fa7..e8b29983b0021 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -293,6 +293,7 @@ static const struct arm64_ftr_bits ftr_id_aa64isar3[] = {
static const struct arm64_ftr_bits ftr_id_aa64pfr0[] = {
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_CSV3_SHIFT, 4, 0),
ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_CSV2_SHIFT, 4, 0),
+ ARM64_FTR_BITS(FTR_HIDDEN, FTR_NONSTRICT, FTR_LOWER_SAFE, ID_AA64PFR0_EL1_RME_SHIFT, 4, 0),
I think we end up exposing this to (any) guest unless we mask it out in
sanitise_id_aa64dfr0_el1(). Do the guests care about the RME version? I
Valid point. I personally don't think this matters. The FEAT_RME alone
is not useful or harmful. I could mask it in KVM as a safe bet.
Is there *any* case where the guest (realm or not) should know it is
running on RME enabled HW? I can perfectly imagine that someone would
We don't do that for Linux Guests at least. The Realms rely on the presence of RSI ABI.
Cheers
Suzuki
implement something looking like CCA on non-RME systems.
M.