On Thu, Aug 01, 2013 at 03:00:12PM +0800, Xiao Guangrong wrote:
> On 07/31/2013 10:48 PM, Gleb Natapov wrote:
> > From: Nadav Har'El <[email protected]>
> >
> > 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 <[email protected]>
> > Signed-off-by: Jun Nakajima <[email protected]>
> > Signed-off-by: Xinhao Xu <[email protected]>
> > Signed-off-by: Yang Zhang <[email protected]>
> > Signed-off-by: Gleb Natapov <[email protected]>
> > ---
> > arch/x86/kvm/mmu.c | 5 +++++
> > arch/x86/kvm/paging_tmpl.h | 37 ++++++++++++++++++++++++++++++++++++-
> > 2 files changed, 41 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> > index 4c4274d..b5273c3 100644
> > --- a/arch/x86/kvm/mmu.c
> > +++ b/arch/x86/kvm/mmu.c
> > @@ -3494,6 +3494,11 @@ 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 2c2f635..762c904 100644
> > --- a/arch/x86/kvm/paging_tmpl.h
> > +++ b/arch/x86/kvm/paging_tmpl.h
> > @@ -23,6 +23,13 @@
> > * so the code in this file is compiled twice, once per pte size.
> > */
> >
> > +/*
> > + * This is used to catch non optimized PT_GUEST_(DIRTY|ACCESS)_SHIFT macro
> > + * uses for EPT without A/D paging type.
> > + */
> > +extern u64 __pure __using_nonexistent_pte_bit(void)
> > + __compiletime_error("wrong use of
> > PT_GUEST_(DIRTY|ACCESS)_SHIFT");
> > +
> > #if PTTYPE == 64
> > #define pt_element_t u64
> > #define guest_walker guest_walker64
> > @@ -58,6 +65,21 @@
> > #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT
> > #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
> > #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
> > + #define PT_GUEST_ACCESSED_MASK 0
> > + #define PT_GUEST_DIRTY_MASK 0
> > + #define PT_GUEST_DIRTY_SHIFT __using_nonexistent_pte_bit()
> > + #define PT_GUEST_ACCESSED_SHIFT __using_nonexistent_pte_bit()
> > + #define CMPXCHG cmpxchg64
> > + #define PT_MAX_FULL_LEVELS 4
> > #else
> > #error Invalid PTTYPE value
> > #endif
> > @@ -115,7 +137,11 @@ static bool FNAME(is_rsvd_bits_set)(struct kvm_mmu
> > *mmu, u64 gpte, int level)
> >
> > static inline int FNAME(is_present_gpte)(unsigned long pte)
> > {
> > +#if PTTYPE != PTTYPE_EPT
> > return is_present_gpte(pte);
> > +#else
> > + return pte & 7;
> > +#endif
> > }
> >
> > static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> > @@ -165,9 +191,14 @@ no_present:
> > static inline unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, u64 gpte)
> > {
> > unsigned access;
> > -
> > +#if PTTYPE == PTTYPE_EPT
> > + access = ((gpte & VMX_EPT_WRITABLE_MASK) ? ACC_WRITE_MASK : 0) |
> > + ((gpte & VMX_EPT_EXECUTABLE_MASK) ? ACC_EXEC_MASK : 0) |
> > + ACC_USER_MASK;
> > +#else
> > access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | ACC_EXEC_MASK;
> > access &= ~(gpte >> PT64_NX_SHIFT);
> > +#endif
>
> Hmm, why not use shadow_x_mask, shadow_user_mask instead? PT_WRITABLE_MASK
> is also suitable for ept, i guess we can remove the "#if/#else/#endif" after
> that.
>
shadow_x_mask and shadow_user_mask do not depend on guest paging mode,
so cannot be used here. Since we have to use ifdefs anyway relying on
VMX_EPT_WRITABLE_MASK == PT_WRITABLE_MASK is not necessary. Makes code
easier to read.
> >
> > return access;
> > }
> > @@ -369,6 +400,7 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
> > access);
> > }
> >
> > +#if PTTYPE != PTTYPE_EPT
> > static int FNAME(walk_addr_nested)(struct guest_walker *walker,
> > struct kvm_vcpu *vcpu, gva_t addr,
> > u32 access)
> > @@ -376,6 +408,7 @@ static int FNAME(walk_addr_nested)(struct guest_walker
> > *walker,
> > return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.nested_mmu,
> > addr, access);
> > }
> > +#endif
> >
> > static bool
> > FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
> > @@ -803,6 +836,7 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu,
> > gva_t vaddr, u32 access,
> > return gpa;
> > }
> >
> > +#if PTTYPE != PTTYPE_EPT
> > static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gva_t vaddr,
> > u32 access,
> > struct x86_exception *exception)
> > @@ -821,6 +855,7 @@ static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu
> > *vcpu, gva_t vaddr,
> >
> > return gpa;
> > }
> > +#endif
>
> Can we move the "walk" together, then one "#if" can be dropped?
Currently walk_addr_nested() is near walk_addr() and gva_to_gpa_nested()
is near gva_to_gpa(). I like this grouping.
--
Gleb.
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