Re: [PATCH] KVM: arm64: vgic-v3: Restrict SEIS workaround to known broken systems

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On 2022-01-22 11:14, Ard Biesheuvel wrote:
On Sat, 22 Jan 2022 at 11:39, Marc Zyngier <maz@xxxxxxxxxx> wrote:

Contrary to what df652bcf1136 ("KVM: arm64: vgic-v3: Work around GICv3
locally generated SErrors") was asserting, there is at least one other
system out there (Cavium ThunderX2) implementing SEIS, and not in
an obviously broken way.

So instead of imposing the M1 workaround on an innocent bystander,
let's limit it to the two known broken Apple implementations.

Fixes: df652bcf1136 ("KVM: arm64: vgic-v3: Work around GICv3 locally generated SErrors")
Reported-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>

Thanks for the fix.

Tested-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx>

Thanks for that.


One nit below.

---
 arch/arm64/kvm/hyp/vgic-v3-sr.c |  3 +++
 arch/arm64/kvm/vgic/vgic-v3.c   | 17 +++++++++++++++--
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c
index 20db2f281cf2..4fb419f7b8b6 100644
--- a/arch/arm64/kvm/hyp/vgic-v3-sr.c
+++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c
@@ -983,6 +983,9 @@ static void __vgic_v3_read_ctlr(struct kvm_vcpu *vcpu, u32 vmcr, int rt)
        val = ((vtr >> 29) & 7) << ICC_CTLR_EL1_PRI_BITS_SHIFT;
        /* IDbits */
        val |= ((vtr >> 23) & 7) << ICC_CTLR_EL1_ID_BITS_SHIFT;
+       /* SEIS */
+       if (kvm_vgic_global_state.ich_vtr_el2 & ICH_VTR_SEIS_MASK)
+               val |= BIT(ICC_CTLR_EL1_SEIS_SHIFT);
        /* A3V */
        val |= ((vtr >> 21) & 1) << ICC_CTLR_EL1_A3V_SHIFT;
        /* EOImode */
diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
index 78cf674c1230..d34a795f730c 100644
--- a/arch/arm64/kvm/vgic/vgic-v3.c
+++ b/arch/arm64/kvm/vgic/vgic-v3.c
@@ -609,6 +609,18 @@ static int __init early_gicv4_enable(char *buf)
 }
 early_param("kvm-arm.vgic_v4_enable", early_gicv4_enable);

+static struct midr_range broken_seis[] = {

Can this be const?

Absolutely. I'll fold that in.

Thanks,

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