| Message ID | 20210323162301.2049595-1-maz@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: Fix CPU interface MMIO compatibility detection | expand |
> -----Original Message----- > From: Marc Zyngier [mailto:maz@kernel.org] > Sent: 23 March 2021 16:23 > To: kvmarm@lists.cs.columbia.edu; kvm@vger.kernel.org; > linux-arm-kernel@lists.infradead.org > Cc: Ard Biesheuvel <ardb@kernel.org>; kernel-team@android.com; Shameerali > Kolothum Thodi <shameerali.kolothum.thodi@huawei.com> > 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 on HiSilicon D06 platform where the original issue(firmware wrongly advertising GICv2-on-v3 compatibility) was reported and all seems to be fine. Though not sure whether this fix is relevant to this particular platform, FWIW, Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com> Thanks, Shameer > Cc: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com> > Fixes: 9739f6ef053f ("KVM: arm64: Workaround firmware wrongly advertising > GICv2-on-v3 compatibility") > Signed-off-by: Marc Zyngier <maz@kernel.org> > --- > 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 ee3682b9873c..39f8f7f9227c 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); > -- > 2.30.0
diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c index ee3682b9873c..39f8f7f9227c 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);
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. Cc: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com> Fixes: 9739f6ef053f ("KVM: arm64: Workaround firmware wrongly advertising GICv2-on-v3 compatibility") Signed-off-by: Marc Zyngier <maz@kernel.org> --- arch/arm64/kvm/hyp/vgic-v3-sr.c | 9 +++++++++ 1 file changed, 9 insertions(+)