From af22df997d71c32304d6835a8b690281063b8010 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Tue, 23 Mar 2021 16:08:18 +0000 Subject: [PATCH] KVM: arm64: Fix CPU interface MMIO compatibility detection In order to detect whether a GICv3 CPU interface is MMIO capable, we switch ICC_SRE_EL1.SRE to 0 and check whether it sticks. However, this is only possible if *ALL* of the HCR_EL2 interrupt overrides are set, and the CPU is perfectly allowed to ignore the write to ICC_SRE_EL1 otherwise. This leads KVM to pretend that a whole bunch of ARMv8.0 CPUs aren't MMIO-capable, and breaks VMs that should work correctly otherwise. Fix this by setting IMO/FMO/IMO before touching ICC_SRE_EL1, and clear them afterwards. This allows us to reliably detect the CPU interface capabilities. Tested-by: Shameerali Kolothum Thodi Fixes: 9739f6ef053f ("KVM: arm64: Workaround firmware wrongly advertising GICv2-on-v3 compatibility") Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/vgic-v3-sr.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c index ee3682b..39f8f7f 100644 --- a/arch/arm64/kvm/hyp/vgic-v3-sr.c +++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c @@ -429,6 +429,13 @@ u64 __vgic_v3_get_gic_config(void) if (has_vhe()) flags = local_daif_save(); + /* + * Table 11-2 "Permitted ICC_SRE_ELx.SRE settings" indicates + * that to be able to set ICC_SRE_EL1.SRE to 0, all the + * interrupt overrides must be set. You've got to love this. + */ + sysreg_clear_set(hcr_el2, 0, HCR_AMO | HCR_FMO | HCR_IMO); + isb(); write_gicreg(0, ICC_SRE_EL1); isb(); @@ -436,6 +443,8 @@ u64 __vgic_v3_get_gic_config(void) write_gicreg(sre, ICC_SRE_EL1); isb(); + sysreg_clear_set(hcr_el2, HCR_AMO | HCR_FMO | HCR_IMO, 0); + isb(); if (has_vhe()) local_daif_restore(flags); -- 2.7.4