Subject: Re: [PATCH v2 01/17] KVM: arm64: Factor out stage 2 page table data from struct kvm

From: Andrew Scull <[email-masked]>
Date: Mon, 13 Jul 2020 10:47:49 +0100

On Mon, Jun 15, 2020 at 02:27:03PM +0100, Marc Zyngier wrote:
> -static void __hyp_text __tlb_switch_to_guest_nvhe(struct kvm *kvm,
> +static void __hyp_text __tlb_switch_to_guest_nvhe(struct kvm_s2_mmu *mmu,
>  						  struct tlb_inv_context *cxt)
>  {
>  	if (cpus_have_final_cap(ARM64_WORKAROUND_SPECULATIVE_AT)) {
> @@ -79,22 +79,19 @@ static void __hyp_text __tlb_switch_to_guest_nvhe(struct kvm *kvm,
>  		isb();
>  	}
>  
> -	/* __load_guest_stage2() includes an ISB for the workaround. */
> -	__load_guest_stage2(kvm);
> -	asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
> +	__load_guest_stage2(mmu);
>  }

Just noticed that this drops the ISB when the speculative AT workaround
is not active.

This alternative is 'backwards' to avoid a double ISB as there is one in
__load_guest_stage2 when the workaround is active. I hope to address
this smell in an upcoming series but, for now, we should at least have
an ISB.

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