On 06/11/2013 07:32 PM, Gleb Natapov wrote: > On Tue, May 21, 2013 at 03:52:12PM +0800, Xiao Guangrong wrote: >> On 05/19/2013 12:52 PM, Jun Nakajima wrote: >>> From: Nadav Har'El <nyh@xxxxxxxxxx> >>> >>> This is the first patch in a series which adds nested EPT support to KVM's >>> nested VMX. Nested EPT means emulating EPT for an L1 guest so that L1 can use >>> EPT when running a nested guest L2. When L1 uses EPT, it allows the L2 guest >>> to set its own cr3 and take its own page faults without either of L0 or L1 >>> getting involved. This often significanlty improves L2's performance over the >>> previous two alternatives (shadow page tables over EPT, and shadow page >>> tables over shadow page tables). >>> >>> This patch adds EPT support to paging_tmpl.h. >>> >>> paging_tmpl.h contains the code for reading and writing page tables. The code >>> for 32-bit and 64-bit tables is very similar, but not identical, so >>> paging_tmpl.h is #include'd twice in mmu.c, once with PTTTYPE=32 and once >>> with PTTYPE=64, and this generates the two sets of similar functions. >>> >>> There are subtle but important differences between the format of EPT tables >>> and that of ordinary x86 64-bit page tables, so for nested EPT we need a >>> third set of functions to read the guest EPT table and to write the shadow >>> EPT table. >>> >>> So this patch adds third PTTYPE, PTTYPE_EPT, which creates functions (prefixed >>> with "EPT") which correctly read and write EPT tables. >>> >>> Signed-off-by: Nadav Har'El <nyh@xxxxxxxxxx> >>> Signed-off-by: Jun Nakajima <jun.nakajima@xxxxxxxxx> >>> Signed-off-by: Xinhao Xu <xinhao.xu@xxxxxxxxx> >>> --- >>> arch/x86/kvm/mmu.c | 5 +++++ >>> arch/x86/kvm/paging_tmpl.h | 43 +++++++++++++++++++++++++++++++++++++++++-- >>> 2 files changed, 46 insertions(+), 2 deletions(-) >>> >>> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c >>> index 117233f..6c1670f 100644 >>> --- a/arch/x86/kvm/mmu.c >>> +++ b/arch/x86/kvm/mmu.c >>> @@ -3397,6 +3397,11 @@ static inline bool is_last_gpte(struct kvm_mmu *mmu, unsigned level, unsigned gp >>> return mmu->last_pte_bitmap & (1 << index); >>> } >>> >>> +#define PTTYPE_EPT 18 /* arbitrary */ >>> +#define PTTYPE PTTYPE_EPT >>> +#include "paging_tmpl.h" >>> +#undef PTTYPE >>> + >>> #define PTTYPE 64 >>> #include "paging_tmpl.h" >>> #undef PTTYPE >>> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h >>> index df34d4a..4c45654 100644 >>> --- a/arch/x86/kvm/paging_tmpl.h >>> +++ b/arch/x86/kvm/paging_tmpl.h >>> @@ -50,6 +50,22 @@ >>> #define PT_LEVEL_BITS PT32_LEVEL_BITS >>> #define PT_MAX_FULL_LEVELS 2 >>> #define CMPXCHG cmpxchg >>> +#elif PTTYPE == PTTYPE_EPT >>> + #define pt_element_t u64 >>> + #define guest_walker guest_walkerEPT >>> + #define FNAME(name) EPT_##name >>> + #define PT_BASE_ADDR_MASK PT64_BASE_ADDR_MASK >>> + #define PT_LVL_ADDR_MASK(lvl) PT64_LVL_ADDR_MASK(lvl) >>> + #define PT_LVL_OFFSET_MASK(lvl) PT64_LVL_OFFSET_MASK(lvl) >>> + #define PT_INDEX(addr, level) PT64_INDEX(addr, level) >>> + #define PT_LEVEL_BITS PT64_LEVEL_BITS >>> + #ifdef CONFIG_X86_64 >>> + #define PT_MAX_FULL_LEVELS 4 >>> + #define CMPXCHG cmpxchg >>> + #else >>> + #define CMPXCHG cmpxchg64 >> >> CMPXHG is only used in FNAME(cmpxchg_gpte), but you commented it later. >> Do we really need it? >> >>> + #define PT_MAX_FULL_LEVELS 2 >> >> And the SDM says: >> >> "It uses a page-walk length of 4, meaning that at most 4 EPT paging-structure >> entriesare accessed to translate a guest-physical address.", Is My SDM obsolete? >> Which kind of process supports page-walk length = 2? >> >> It seems your patch is not able to handle the case that the guest uses walk-lenght = 2 >> which is running on the host with walk-lenght = 4. >> (plrease refer to how to handle sp->role.quadrant in FNAME(get_level1_sp_gpa) in >> the current code.) >> > But since EPT always has 4 levels on all existing cpus it is not an issue and the only case > that we should worry about is guest walk-lenght == host walk-lenght == 4, or have I Yes. I totally agree with you, but... > misunderstood what you mean here? What confused me is that this patch defines "#define PT_MAX_FULL_LEVELS 2", so i asked the question: "Which kind of process supports page-walk length = 2". Sorry, there is a typo in my origin comments. "process" should be "processor" or "CPU". -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
