On Mon, Jun 22, 2015 at 2:56 PM, Ed White <edmund.h.wh...@intel.com> wrote:
> Add the remaining routines required to support enabling the alternate
> p2m functionality.
>
> Signed-off-by: Ed White <edmund.h.wh...@intel.com>
> ---
> xen/arch/x86/hvm/hvm.c | 60 +++++-
> xen/arch/x86/mm/hap/Makefile | 1 +
> xen/arch/x86/mm/hap/altp2m_hap.c | 103 +++++++++
> xen/arch/x86/mm/p2m-ept.c | 3 +
> xen/arch/x86/mm/p2m.c | 405
> ++++++++++++++++++++++++++++++++++++
> xen/include/asm-x86/hvm/altp2mhvm.h | 4 +
> xen/include/asm-x86/p2m.h | 33 +++
> 7 files changed, 601 insertions(+), 8 deletions(-)
> create mode 100644 xen/arch/x86/mm/hap/altp2m_hap.c
>
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index d75c12d..b758ee1 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -2786,10 +2786,11 @@ int hvm_hap_nested_page_fault(paddr_t gpa,
> unsigned long gla,
> p2m_access_t p2ma;
> mfn_t mfn;
> struct vcpu *v = current;
> - struct p2m_domain *p2m;
> + struct p2m_domain *p2m, *hostp2m;
> int rc, fall_through = 0, paged = 0;
> int sharing_enomem = 0;
> vm_event_request_t *req_ptr = NULL;
> + int altp2m_active = 0;
>
> /* On Nested Virtualization, walk the guest page table.
> * If this succeeds, all is fine.
> @@ -2845,15 +2846,33 @@ int hvm_hap_nested_page_fault(paddr_t gpa,
> unsigned long gla,
> {
> if ( !handle_mmio_with_translation(gla, gpa >> PAGE_SHIFT, npfec)
> )
> hvm_inject_hw_exception(TRAP_gp_fault, 0);
> - rc = 1;
> - goto out;
> + return 1;
> }
>
> - p2m = p2m_get_hostp2m(v->domain);
> - mfn = get_gfn_type_access(p2m, gfn, &p2mt, &p2ma,
> + altp2m_active = altp2mhvm_active(v->domain);
> +
> + /* Take a lock on the host p2m speculatively, to avoid potential
> + * locking order problems later and to handle unshare etc.
> + */
> + hostp2m = p2m_get_hostp2m(v->domain);
> + mfn = get_gfn_type_access(hostp2m, gfn, &p2mt, &p2ma,
> P2M_ALLOC | (npfec.write_access ?
> P2M_UNSHARE : 0),
> NULL);
>
> + if ( altp2m_active )
> + {
> + if ( altp2mhvm_hap_nested_page_fault(v, gpa, gla, npfec, &p2m) ==
> 1 )
> + {
> + /* entry was lazily copied from host -- retry */
>
So I'm not fully following this logic here. I can see that the altp2m entry
got copied from the host. Why is there a need for the retry, why not just
continue?
> + __put_gfn(hostp2m, gfn);
> + return 1;
> + }
> +
> + mfn = get_gfn_type_access(p2m, gfn, &p2mt, &p2ma, 0, NULL);
> + }
> + else
> + p2m = hostp2m;
> +
> /* Check access permissions first, then handle faults */
> if ( mfn_x(mfn) != INVALID_MFN )
> {
>
--
[image: www.novetta.com]
Tamas K Lengyel
Senior Security Researcher
7921 Jones Branch Drive
McLean VA 22102
Email tleng...@novetta.com
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