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SubjectRe: [PATCH v2 11/17] kvm: arm64: Configure VTCR per VM
Hi Suzuki,

On 27/03/18 14:15, Suzuki K Poulose wrote:
> We set VTCR_EL2 very early during the stage2 init and don't
> touch it ever. This is fine as we had a fixed IPA size. This
> patch changes the behavior to set the VTCR for a given VM,
> depending on its stage2 table. The common configuration for
> VTCR is still performed during the early init as we have to
> retain the hardware access flag update bits (VTCR_EL2_HA)
> per CPU (as they are only set for the CPUs which are capabile).

(Nit: capable)

> The bits defining the number of levels in the page table (SL0)
> and and the size of the Input address to the translation (T0SZ)
> are programmed for each VM upon entry to the guest.

> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 870f4b1..5ccd3ae 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -164,6 +164,12 @@ static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
> static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu)
> {
> struct kvm *kvm = kern_hyp_va(vcpu->kvm);
> + u64 vtcr = read_sysreg(vtcr_el2);
> +
> + vtcr &= ~VTCR_EL2_PRIVATE_MASK;
> + vtcr |= VTCR_EL2_SL0(kvm_stage2_levels(kvm)) |
> + VTCR_EL2_T0SZ(kvm_phys_shift(kvm));
> + write_sysreg(vtcr, vtcr_el2);
> write_sysreg(kvm->arch.vttbr, vttbr_el2);
> }

Do we need to set this register for tlb maintenance too?
e.g. tlbi for a 3-level-stage2 vm when a 2-level-stage2 vm's vtcr is loaded...

(The ARM-ARM has 'Any of the bits of VTCR_EL2 are permitted to be cached in a TLB'.)



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