Re: [PATCH v3 11/19] KVM: MMU: filter out the mmio pfn from the fault pfn

Marcelo Tosatti
2011-07-06T17:39:27Z

On Thu, Jun 30, 2011 at 04:24:06PM +0800, Xiao Guangrong wrote:
> If the page fault is caused by mmio, the gfn can not be found in memslots, and
> 'bad_pfn' is returned on gfn_to_hva path, so we can use 'bad_pfn' to identify
> the mmio page fault.
> And, to clarify the meaning of mmio pfn, we return fault page instead of bad
> page when the gfn is not allowd to prefetch
>
> Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
> ---
> arch/x86/kvm/mmu.c | 4 ++--
> include/linux/kvm_host.h | 5 +++++
> virt/kvm/kvm_main.c | 16 ++++++++++++++--
> 3 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 5334b4e..96a7ed4 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -2085,8 +2085,8 @@ static pfn_t pte_prefetch_gfn_to_pfn(struct kvm_vcpu *vcpu, gfn_t gfn,
>
> slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, no_dirty_log);
> if (!slot) {
> - get_page(bad_page);
> - return page_to_pfn(bad_page);
> + get_page(fault_page);
> + return page_to_pfn(fault_page);
> }
>
> hva = gfn_to_hva_memslot(slot, gfn);
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 31ebb59..3e548e8 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -326,12 +326,17 @@ static inline struct kvm_memslots *kvm_memslots(struct kvm *kvm)
> static inline int is_error_hpa(hpa_t hpa) { return hpa >> HPA_MSB; }
>
> extern struct page *bad_page;
> +extern struct page *fault_page;
> +
> extern pfn_t bad_pfn;
> +extern pfn_t fault_pfn;
>
> int is_error_page(struct page *page);
> int is_error_pfn(pfn_t pfn);
> int is_hwpoison_pfn(pfn_t pfn);
> int is_fault_pfn(pfn_t pfn);
> +int is_mmio_pfn(pfn_t pfn);
> +int is_invalid_pfn(pfn_t pfn);
> int kvm_is_error_hva(unsigned long addr);
> int kvm_set_memory_region(struct kvm *kvm,
> struct kvm_userspace_memory_region *mem,
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 11d2783..c7d41d4 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -101,8 +101,8 @@ static bool largepages_enabled = true;
> static struct page *hwpoison_page;
> static pfn_t hwpoison_pfn;
>
> -static struct page *fault_page;
> -static pfn_t fault_pfn;
> +struct page *fault_page;
> +pfn_t fault_pfn;
>
> inline int kvm_is_mmio_pfn(pfn_t pfn)
> {
> @@ -931,6 +931,18 @@ int is_fault_pfn(pfn_t pfn)
> }
> EXPORT_SYMBOL_GPL(is_fault_pfn);
>
> +int is_mmio_pfn(pfn_t pfn)
> +{
> + return pfn == bad_pfn;
> +}
> +EXPORT_SYMBOL_GPL(is_mmio_pfn);

Please use another name this conflicts with real mmio pfn,
see kvm_is_mmio_pfn. "noslot_pfn" is meaningful to me.