Re: [PATCH v5 12/12] KVM: arm64: Use local TLBI on permission relaxation

[Vladimir Murzin <vladimir.murzin@xxxxxxx>]

On 3/1/23 21:09, Ricardo Koller wrote:
> Second, KVM does not set the VTTBR_EL2.CnP bit, so each
> PE has its own TLB entry for the same page. KVM could tolerate that when
> doing permission relaxation (i.e., not having changes broadcasted to all
> PEs).

I'm might be missing something, but it seems that we do set CnP bit, at
least in v6.2 we have

arch/arm64/include/asm/kvm_mmu.h

static __always_inline u64 kvm_get_vttbr(struct kvm_s2_mmu *mmu)
{
        struct kvm_vmid *vmid = &mmu->vmid;
        u64 vmid_field, baddr;
        u64 cnp = system_supports_cnp() ? VTTBR_CNP_BIT : 0;

        baddr = mmu->pgd_phys;
        vmid_field = atomic64_read(&vmid->id) << VTTBR_VMID_SHIFT;
        vmid_field &= VTTBR_VMID_MASK(kvm_arm_vmid_bits);
        return kvm_phys_to_vttbr(baddr) | vmid_field | cnp;
}

Cheers
Vladimir