Re: [PATCH v2 2/2] KVM: arm64: Workaround firmware wrongly advertising GICv2-on-v3 compatibility

On 2021-01-19 10:09, Shameerali Kolothum Thodi wrote:

quoted

-----Original Message-----
From: Marc Zyngier [mailto:maz@kernel.org]
Sent: 15 January 2021 14:15
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Linux ARM <redacted>; kvmarm
[off-list ref]; Shameerali Kolothum Thodi
[off-list ref]; James Morse
[off-list ref]; Julien Thierry [off-list ref];
Suzuki K Poulose [off-list ref]; Android Kernel Team
[off-list ref]
Subject: Re: [PATCH v2 2/2] KVM: arm64: Workaround firmware wrongly
advertising GICv2-on-v3 compatibility

On 2021-01-15 14:08, Ard Biesheuvel wrote:

quoted

On Fri, 15 Jan 2021 at 15:03, Marc Zyngier [off-list ref] wrote:

[...]

quoted

quoted

diff --git a/arch/arm64/kvm/vgic/vgic-v3.c

b/arch/arm64/kvm/vgic/vgic-v3.c index 8e7bf3151057..67b27b47312b
100644

--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c

@@ -584,8 +584,10 @@ 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;

        /*

@@ -605,13 +607,15 @@ 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("CPU interface incapable of MMIO access\n");

Could we include FW_BUG here to stress that this is a firmware problem?

Absolutely! That's what it now looks like:

[    2.648452] kvm [1]: IPA Size Limit: 40 bits
[    2.649259] [Firmware Bug]: CPU interface incapable of MMIO access
[    2.649620] kvm [1]: disabling GICv2 emulation
[    2.650227] kvm [1]: GIC system register CPU interface enabled
[    2.652004] kvm [1]: vgic interrupt IRQ9
[    2.655623] kvm [1]: VHE mode initialized successfully

Updated version pushed out.

Is there a v3 for this series? I couldn't find one.

Nope, I didn't think it was useful to send another series for such
a minor change.

Anyways, tested this series on a D06 with faulty firmware and it is
working as expected.
FWIW,

   Tested-by: Shameer Kolothum [off-list ref]

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

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