On Wed, 2026-01-07 at 11:19 +0000, Jonathan Cameron wrote:

On Fri, 19 Dec 2025 15:52:39 +0000
Sascha Bischoff [off-list ref] wrote:

quoted

Extend the existing FGT/FGU infrastructure to include the GICv5
trap
registers (ICH_HFGRTR_EL2, ICH_HFGWTR_EL2, ICH_HFGITR_EL2). This
involves mapping the trap registers and their bits to the
corresponding feature that introduces them (FEAT_GCIE for all, in
this
case), and mapping each trap bit to the system register/instruction
controlled by it.

As of this change, none of the GICv5 instructions or register
accesses
are being trapped.

Signed-off-by: Sascha Bischoff <redacted>

Hi Sascha,

Superficial stuff only on code flow to make it easier to extend next
time.

Jonathan

quoted

diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
index 3845b188551b6..5f57dc07cc482 100644
--- a/arch/arm64/kvm/config.c
+++ b/arch/arm64/kvm/config.c

quoted

@@ -1511,11 +1595,19 @@ void kvm_vcpu_load_fgt(struct kvm_vcpu

*vcpu)
 	__compute_fgt(vcpu, HAFGRTR_EL2);
 
 	if (!cpus_have_final_cap(ARM64_HAS_FGT2))
-		return;
+		goto skip_fgt2;

Nicer to avoid more complex code flow and just make the next
block an if.

	if (cpus_have_final_cap(ARM64_HAS_FGT2)) {
		__compute_fgt(vcpu, HFGRTR2_EL2);
		__compute_fgt(vcpu, HFGWTR2_EL2);
		__compute_fgt(vcpu, HFGITR2_EL2);
		__compute_fgt(vcpu, HDFGRTR2_EL2);
		__compute_fgt(vcpu, HDFGWTR2_EL2);
	}

quoted

 
 	__compute_fgt(vcpu, HFGRTR2_EL2);
 	__compute_fgt(vcpu, HFGWTR2_EL2);
 	__compute_fgt(vcpu, HFGITR2_EL2);
 	__compute_fgt(vcpu, HDFGRTR2_EL2);
 	__compute_fgt(vcpu, HDFGWTR2_EL2);
+
+skip_fgt2:
+	if (!cpus_have_final_cap(ARM64_HAS_GICV5_CPUIF))

Given the above shows this code sometimes gets extended I'd
be tempted to just go with
	if (cpus_have_final_cap(ARM64_HAS_GICV5_CPUIF)) {
		__compute_fgt(vcpu, ICH_HFGRTR_EL2);
		__compute_fgt(vcpu, ICH_HFGWTR_EL2);
		__compute_fgt(vcpu, ICH_HFGITR_EL2);
	}

From the start and avoid future churn or goto nasties.

Yeah, you're probably right. Done.

Thanks,
Sascha

quoted

	
+		return;
+
+	__compute_fgt(vcpu, ICH_HFGRTR_EL2);
+	__compute_fgt(vcpu, ICH_HFGWTR_EL2);
+	__compute_fgt(vcpu, ICH_HFGITR_EL2);
 }