Re: [PATCH v2 10/11] powerpc/kvm: Store the MMU mode in the PACA on KVM exit

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On Thu, Nov 23, 2017 at 03:36:18PM +1100, Benjamin Herrenschmidt wrote:
> This stores the MMU mode (real vs. virt) in the PACA on exceptions
> that do a KVM test.
> 
> At the moment, we do this unconditionally in those exceptions due
> to how the macro system is put together. In the future we could
> find a way to only do it when actually exiting a guest.
> 
> This will avoid a pile of mfmsr in the KVM exit path

Comments below...

> diff --git a/arch/powerpc/include/asm/kvm_book3s_asm.h b/arch/powerpc/include/asm/kvm_book3s_asm.h
> index 83596f32f50b..7775a278e56e 100644
> --- a/arch/powerpc/include/asm/kvm_book3s_asm.h
> +++ b/arch/powerpc/include/asm/kvm_book3s_asm.h
> @@ -118,6 +118,7 @@ struct kvmppc_host_state {
>  	void __iomem *xive_tima_phys;
>  	void __iomem *xive_tima_virt;
>  	u32 saved_xirr;
> +	u8 exit_virt;		/* MMU mode on exception exit */

This is being added in the #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
section of this struct, but as far as I can see we will need the new
field in the case where only PR and not HV is configured.  Did you try
compiling a PR-only config?

Paul.



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