Re: [PATCH 09/13] KVM: PPC: e500: enable magic page

[Alexander Graf <agraf@suse.de>]

On 05/18/2011 01:42 AM, Scott Wood wrote:
> This is a shared page used for paravirtualization.  It is always present
> in the guest kernel's effective address space at the address indicated
> by the hypercall that enables it.
>
> The physical address specified by the hypercall is not used, as
> e500 does not have real mode.

This also requires a documentation change.

> Signed-off-by: Scott Wood<scottwood@freescale.com>
> ---
>   arch/powerpc/include/asm/kvm_ppc.h |    1 +
>   arch/powerpc/kvm/booke.c           |   11 +++++++++++
>   arch/powerpc/kvm/e500_tlb.c        |   22 +++++++++++++++++++++-
>   arch/powerpc/kvm/powerpc.c         |    9 +++++----
>   4 files changed, 38 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index 9345238..c662f14 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -109,6 +109,7 @@ extern void kvmppc_booke_exit(void);
>
>   extern void kvmppc_core_destroy_mmu(struct kvm_vcpu *vcpu);
>   extern int kvmppc_kvm_pv(struct kvm_vcpu *vcpu);
> +extern void kvmppc_map_magic(struct kvm_vcpu *vcpu);
>
>   /*
>    * Cuts out inst bits with ordering according to spec.
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 85b9391..036625e 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -472,6 +472,17 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
>   		gpa_t gpaddr;
>   		gfn_t gfn;
>
> +#ifdef CONFIG_KVM_E500
> +		if (!(vcpu->arch.shared->msr&  MSR_PR)&&
> +		    (eaddr&  PAGE_MASK) = vcpu->arch.magic_page_ea) {
> +			kvmppc_map_magic(vcpu);
> +			kvmppc_account_exit(vcpu, DTLB_VIRT_MISS_EXITS);
> +			r = RESUME_GUEST;
> +
> +			break;
> +		}
> +#endif
> +
>   		/* Check the guest TLB. */
>   		gtlb_index = kvmppc_mmu_dtlb_index(vcpu, eaddr);
>   		if (gtlb_index<  0) {
> diff --git a/arch/powerpc/kvm/e500_tlb.c b/arch/powerpc/kvm/e500_tlb.c
> index 7f808c5..c09e642 100644
> --- a/arch/powerpc/kvm/e500_tlb.c
> +++ b/arch/powerpc/kvm/e500_tlb.c
> @@ -76,7 +76,8 @@ static inline unsigned int tlb0_get_next_victim(
>
>   static inline unsigned int tlb1_max_shadow_size(void)
>   {
> -	return tlb1_entry_num - tlbcam_index;
> +	/* reserve one entry for magic page */
> +	return tlb1_entry_num - tlbcam_index - 1;
>   }
>
>   static inline int tlbe_is_writable(struct tlbe *tlbe)
> @@ -142,6 +143,25 @@ static inline void write_host_tlbe(struct kvmppc_vcpu_e500 *vcpu_e500,
>   	}
>   }
>
> +void kvmppc_map_magic(struct kvm_vcpu *vcpu)
> +{
> +	struct tlbe magic;
> +	ulong shared_page = ((ulong)vcpu->arch.shared)&  PAGE_MASK;
> +	pfn_t pfn;
> +
> +	pfn = (pfn_t)virt_to_phys((void *)shared_page)>>  PAGE_SHIFT;
> +	get_page(pfn_to_page(pfn));
> +
> +	magic.mas1 = MAS1_VALID | MAS1_TS |
> +		     MAS1_TSIZE(BOOK3E_PAGESZ_4K);
> +	magic.mas2 = vcpu->arch.magic_page_ea | MAS2_M;
> +	magic.mas3 = (pfn<<  PAGE_SHIFT) |
> +		     MAS3_SW | MAS3_SR | MAS3_UW | MAS3_UR;
> +	magic.mas7 = pfn>>  (32 - PAGE_SHIFT);
> +
> +	__write_host_tlbe(&magic, MAS0_TLBSEL(1) | MAS0_ESEL(tlbcam_index));

It's a 4k page, so why use TLB1? Also, you add this as PID0 mapping, no? 
Shouldn't it be restricted to the guest's kernel?

Alex