From: Marc Zyngier <maz@kernel.org>
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
Date: Tue, 23 Mar 2021 16:23:01 +0000 [thread overview]
Message-ID: <20210323162301.2049595-1-maz@kernel.org> (raw)
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(+)
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
next reply other threads:[~2021-03-23 16:24 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-23 16:23 Marc Zyngier [this message]
2021-03-24 15:47 ` [PATCH] KVM: arm64: Fix CPU interface MMIO compatibility detection Shameerali Kolothum Thodi
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