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

[Marc Zyngier]

On 2022-01-22 11:14, Ard Biesheuvel wrote:
> On Sat, 22 Jan 2022 at 11:39, Marc Zyngier <maz at kernel.org> 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 at kernel.org>
>> Signed-off-by: Marc Zyngier <maz at kernel.org>
> 
> Thanks for the fix.
> 
> Tested-by: Ard Biesheuvel <ardb at kernel.org>
> Acked-by: Ard Biesheuvel <ardb at kernel.org>

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...