Re: [PATCH v5 48/49] KVM: selftests: Add VGICv5 IST save/restore coverage

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Missing Context Synchronization Event (ISB) after control-plane system register writes.
--

--- Patch [48]: [PATCH v5 48/49] KVM: selftests: Add VGICv5 IST save/restore coverage ---
commit 3f2c979e78365e70421bcaaf39f350d8b4a83086
Author: Sascha Bischoff <Sascha.Bischoff@arm.com>

KVM: selftests: Add VGICv5 IST save/restore coverage

Add end-to-end VGICv5 IST save/restore coverage. The test verifies that
interrupt state saved from the ISTs can be restored into a fresh VM before
first run and then consumed by the guest.

> diff --git a/tools/testing/selftests/kvm/arm64/vgic_v5.c b/tools/testing/selftests/kvm/arm64/vgic_v5.c
> index 71bda5661c74e..47e147bc14b87 100644
> --- a/tools/testing/selftests/kvm/arm64/vgic_v5.c
> +++ b/tools/testing/selftests/kvm/arm64/vgic_v5.c
[ ... ]
> @@ -359,6 +406,165 @@ static void guest_lpi_code(void)
[ ... ]
> +static void guest_ist_restore_code(void)
> +{
> +	local_irq_disable();
> +
> +	gicv5_cpu_enable_interrupts();
> +
> +	if (!guest_get_vcpuid())

[Severity: High]
This is a pre-existing issue, but should gicv5_cpu_enable_interrupts()
issue an isb() before it returns?

Looking at the implementation of gicv5_cpu_enable_interrupts() in both the
host kernel driver (drivers/irqchip/irq-gic-v5.c) and the selftest helper
(tools/testing/selftests/kvm/include/arm64/gic_v5.h), it writes to control
plane system registers like SYS_ICC_CR0_EL1 without an explicit context
synchronization event.

In this new test code, we perform a conditional branch based on
guest_get_vcpuid() immediately after returning from the function. Without an
isb(), could this conditional instruction be executed against an
architecturally undefined pipeline state?

> +		gicv5_set_pcr(VGIC_V5_IST_PRIO_HIGH);
> +
> +	GUEST_SYNC(GUEST_CMD_IS_READY);
> +
> +	local_irq_enable();
> +
> +	while (1)
> +		wfi();
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260807111159.429128-1-sascha.bischoff@arm.com?part=48