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KVM: arm64: Workaround firmware wrongly advertising GICv2-on-v3 compatibility

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It looks like we have broken firmware out there that wrongly advertises
a GICv2 compatibility interface, despite the CPUs not being able to deal
with it.

To work around this, check that the CPU initialising KVM is actually able
to switch to MMIO instead of system registers, and use that as a
precondition to enable GICv2 compatibility in KVM.

Note that the detection happens on a single CPU. If the firmware is
lying *and* that the CPUs are asymetric, all hope is lost anyway.

Reported-by: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
Tested-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Message-Id: <20210305185254.3730990-8-maz@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Marc Zyngier 2021-03-05 18:52:53 +00:00 committed by Paolo Bonzini
parent b9d699e269
commit 9739f6ef05
2 changed files with 39 additions and 4 deletions
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35
arch/arm64/kvm/hyp/vgic-v3-sr.c
View File

@ -408,11 +408,42 @@ void __vgic_v3_init_lrs(void)
/*
* Return the GIC CPU configuration:
* - [31:0] ICH_VTR_EL2
* - [63:32] RES0
* - [62:32] RES0
* - [63] MMIO (GICv2) capable
*/
u64 __vgic_v3_get_gic_config(void)
{
return read_gicreg(ICH_VTR_EL2);
u64 val, sre = read_gicreg(ICC_SRE_EL1);
unsigned long flags = 0;
/*
* To check whether we have a MMIO-based (GICv2 compatible)
* CPU interface, we need to disable the system register
* view. To do that safely, we have to prevent any interrupt
* from firing (which would be deadly).
*
* Note that this only makes sense on VHE, as interrupts are
* already masked for nVHE as part of the exception entry to
* EL2.
*/
if (has_vhe())
flags = local_daif_save();
write_gicreg(0, ICC_SRE_EL1);
isb();
val = read_gicreg(ICC_SRE_EL1);
write_gicreg(sre, ICC_SRE_EL1);
isb();
if (has_vhe())
local_daif_restore(flags);
val = (val & ICC_SRE_EL1_SRE) ? 0 : (1ULL << 63);
val |= read_gicreg(ICH_VTR_EL2);
return val;
}
u64 __vgic_v3_read_vmcr(void)

8
arch/arm64/kvm/vgic/vgic-v3.c
View File

@ -575,8 +575,10 @@ early_param("kvm-arm.vgic_v4_enable", early_gicv4_enable);
int vgic_v3_probe(const struct gic_kvm_info *info)
{
u64 ich_vtr_el2 = kvm_call_hyp_ret(__vgic_v3_get_gic_config);
bool has_v2;
int ret;
has_v2 = ich_vtr_el2 >> 63;
ich_vtr_el2 = (u32)ich_vtr_el2;
/*
@ -596,13 +598,15 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
gicv4_enable ? "en" : "dis");
}
kvm_vgic_global_state.vcpu_base = 0;
if (!info->vcpu.start) {
kvm_info("GICv3: no GICV resource entry\n");
kvm_vgic_global_state.vcpu_base = 0;
} else if (!has_v2) {
pr_warn(FW_BUG "CPU interface incapable of MMIO access\n");
} else if (!PAGE_ALIGNED(info->vcpu.start)) {
pr_warn("GICV physical address 0x%llx not page aligned\n",
(unsigned long long)info->vcpu.start);
kvm_vgic_global_state.vcpu_base = 0;
} else {
kvm_vgic_global_state.vcpu_base = info->vcpu.start;
kvm_vgic_global_state.can_emulate_gicv2 = true;