Re: [PATCH 8/8] KVM: PPC: Add cache flush on page map

[Scott Wood <scottwood@freescale.com>]

On 08/07/2012 05:57 AM, Alexander Graf wrote:
> When we map a page that wasn't icache cleared before, do so when first
> mapping it in KVM using the same information bits as the Linux mapping
> logic. That way we are 100% sure that any page we map does not have stale
> entries in the icache.
> 
> What we really would need is a method to flush the icache only when we
> actually map a page executable for the guest. But with the current
> abstraction that is hard to do, and this way we don't have a huge performance
> penalty, so better be safe now and micro optimize things later.
> 
> Signed-off-by: Alexander Graf <agraf@suse.de>
> ---
>  arch/powerpc/include/asm/kvm_host.h |   10 ++++++++++
>  arch/powerpc/mm/mem.c               |    1 +
>  2 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index ed75bc9..c0a2fc1 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -33,6 +33,7 @@
>  #include <asm/kvm_asm.h>
>  #include <asm/processor.h>
>  #include <asm/page.h>
> +#include <asm/cacheflush.h>
>  
>  #define KVM_MAX_VCPUS		NR_CPUS
>  #define KVM_MAX_VCORES		NR_CPUS
> @@ -550,5 +551,14 @@ struct kvm_vcpu_arch {
>  #define KVM_MMIO_REG_FQPR	0x0060
>  
>  #define __KVM_HAVE_ARCH_WQP
> +#define __KVM_HAVE_ARCH_MAP_PAGE
> +static inline void kvm_arch_map_page(struct page *page)
> +{
> +	/* Need to invalidate the icache for new pages */
> +	if (!test_bit(PG_arch_1, &page->flags)) {
> +		flush_dcache_icache_page(page);
> +		set_bit(PG_arch_1, &page->flags);
> +	}
> +}

Shouldn't this test CPU_FTR_COHERENT_ICACHE?

-Scott