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SubjectRe: [RFC 35/55] KVM: arm/arm64: Support mmu for the virtual EL2 execution
On Mon, Jan 09, 2017 at 01:24:31AM -0500, Jintack Lim wrote:
> From: Christoffer Dall <christoffer.dall@linaro.org>
>
> When running a guest hypervisor in virtual EL2, the translation context
> has to be separate from the rest of the system, including the guest
> EL1/0 translation regime, so we allocate a separate VMID for this mode.
>
> Considering that we have two different vttbr values due to separate
> VMIDs, it's racy to keep a vttbr value in a struct (kvm_s2_mmu) and
> share it between multiple vcpus. So, keep the vttbr value per vcpu.
>
> Hypercalls to flush tlb now have vttbr as a parameter instead of mmu,
> since mmu structure does not have vttbr any more.
>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
> ---
> arch/arm/include/asm/kvm_asm.h | 6 ++--
> arch/arm/include/asm/kvm_emulate.h | 4 +++
> arch/arm/include/asm/kvm_host.h | 14 ++++++---
> arch/arm/include/asm/kvm_mmu.h | 11 +++++++
> arch/arm/kvm/arm.c | 60 +++++++++++++++++++-----------------
> arch/arm/kvm/hyp/switch.c | 4 +--
> arch/arm/kvm/hyp/tlb.c | 15 ++++-----
> arch/arm/kvm/mmu.c | 9 ++++--
> arch/arm64/include/asm/kvm_asm.h | 6 ++--
> arch/arm64/include/asm/kvm_emulate.h | 8 +++++
> arch/arm64/include/asm/kvm_host.h | 14 ++++++---
> arch/arm64/include/asm/kvm_mmu.h | 11 +++++++
> arch/arm64/kvm/hyp/switch.c | 4 +--
> arch/arm64/kvm/hyp/tlb.c | 16 ++++------
> 14 files changed, 112 insertions(+), 70 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_asm.h b/arch/arm/include/asm/kvm_asm.h
> index 36e3856..aa214f7 100644
> --- a/arch/arm/include/asm/kvm_asm.h
> +++ b/arch/arm/include/asm/kvm_asm.h
> @@ -65,9 +65,9 @@
> extern char __kvm_hyp_vector[];
>
> extern void __kvm_flush_vm_context(void);
> -extern void __kvm_tlb_flush_vmid_ipa(struct kvm_s2_mmu *mmu, phys_addr_t ipa);
> -extern void __kvm_tlb_flush_vmid(struct kvm_s2_mmu *mmu);
> -extern void __kvm_tlb_flush_local_vmid(struct kvm_s2_mmu *mmu);
> +extern void __kvm_tlb_flush_vmid_ipa(u64 vttbr, phys_addr_t ipa);
> +extern void __kvm_tlb_flush_vmid(u64 vttbr);
> +extern void __kvm_tlb_flush_local_vmid(u64 vttbr);
>
> extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
>
> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
> index 05d5906..6285f4f 100644
> --- a/arch/arm/include/asm/kvm_emulate.h
> +++ b/arch/arm/include/asm/kvm_emulate.h
> @@ -305,4 +305,8 @@ static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
> }
> }
>
> +static inline struct kvm_s2_vmid *vcpu_get_active_vmid(struct kvm_vcpu *vcpu)
> +{
> + return &vcpu->kvm->arch.mmu.vmid;
> +}
> #endif /* __ARM_KVM_EMULATE_H__ */
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index f84a59c..da45394 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -53,16 +53,18 @@
> int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
> void kvm_reset_coprocs(struct kvm_vcpu *vcpu);
>
> -struct kvm_s2_mmu {
> +struct kvm_s2_vmid {
> /* The VMID generation used for the virt. memory system */
> u64 vmid_gen;
> u32 vmid;
> +};
> +
> +struct kvm_s2_mmu {
> + struct kvm_s2_vmid vmid;
> + struct kvm_s2_vmid el2_vmid;

So this is subtle: We use struct kvm_s2_mmu for the stage-2 context
used for the L1 VM, and for the L2 VM as well, right? But only in the
first case can the el2_vmid have any valid meaning, and it's simply
ignored in other contexts.

Not sure if we can improve on this data structure design, but we could
at least add a comment on this somewhere.

Thanks,
-Christoffer

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