Re: [PATCH 6/8] kvm/mmu: add support for another level to page walker

Avi Kivity
2009-06-20T11:20:13Z

On 06/19/2009 04:16 PM, Joerg Roedel wrote:
> The page walker may be used with nested paging too when accessing mmio areas.
> Make it support the additional page-level too.
>
> Signed-off-by: Joerg Roedel<joerg.roedel@amd.com>
> ---
> arch/x86/kvm/mmu.c | 6 ++++++
> arch/x86/kvm/paging_tmpl.h | 16 ++++++++++++++++
> 2 files changed, 22 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index ef2396d..fc0e2fc 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -117,6 +117,11 @@ module_param(oos_shadow, bool, 0644);
> #define PT64_DIR_BASE_ADDR_MASK \
> (PT64_BASE_ADDR_MASK& ~((1ULL<< (PAGE_SHIFT + PT64_LEVEL_BITS)) - 1))
>
> +#define PT64_PDPE_BASE_ADDR_MASK \
> + (PT64_BASE_ADDR_MASK& ~(1ULL<< (PAGE_SHIFT + (2 * PT64_LEVEL_BITS))))
> +#define PT64_PDPE_OFFSET_MASK \
> + (PT64_BASE_ADDR_MASK& (1ULL<< (PAGE_SHIFT + (2 * PT64_LEVEL_BITS))))
> +
> #define PT32_BASE_ADDR_MASK PAGE_MASK
> #define PT32_DIR_BASE_ADDR_MASK \
> (PAGE_MASK& ~((1ULL<< (PAGE_SHIFT + PT32_LEVEL_BITS)) - 1))
> @@ -130,6 +135,7 @@ module_param(oos_shadow, bool, 0644);
> #define PFERR_RSVD_MASK (1U<< 3)
> #define PFERR_FETCH_MASK (1U<< 4)
> +static gfn_t gpte_to_gfn_pdpe(pt_element_t gpte)
> +{
> + return (gpte& PT64_PDPE_BASE_ADDR_MASK)>> PAGE_SHIFT;
> +}
> +
> static bool FNAME(cmpxchg_gpte)(struct kvm *kvm,
> gfn_t table_gfn, unsigned index,
> pt_element_t orig_pte, pt_element_t new_pte)
> @@ -201,6 +207,15 @@ walk:
> break;
> }
>
> + if (walker->level == PT_PDPE_LEVEL&&
> + (pte& PT_PAGE_SIZE_MASK)&&
> + is_long_mode(vcpu)) {
> + walker->gfn = gpte_to_gfn_pdpe(pte);
> + walker->gfn += (addr& PT64_PDPE_OFFSET_MASK)
> + >> PAGE_SHIFT;
> + break;
> + }
> +
> pt_access = pte_access;
>

It would be cleaner to merge this with the 2MB check earlier (and to
rename and parametrise gpte_to_gfn_pde() rather than duplicate it).

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.