From: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
To: Jun Nakajima <jun.nakajima@intel.com>
Cc: kvm@vger.kernel.org, Gleb Natapov <gleb@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v3 03/13] nEPT: Add EPT tables support to paging_tmpl.h
Date: Tue, 21 May 2013 15:52:12 +0800 [thread overview]
Message-ID: <519B27AC.6090903@linux.vnet.ibm.com> (raw)
In-Reply-To: <1368939152-11406-3-git-send-email-jun.nakajima@intel.com>
On 05/19/2013 12:52 PM, Jun Nakajima wrote:
> From: Nadav Har'El <nyh@il.ibm.com>
>
> 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@il.ibm.com>
> Signed-off-by: Jun Nakajima <jun.nakajima@intel.com>
> Signed-off-by: Xinhao Xu <xinhao.xu@intel.com>
> ---
> 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.)
> + #endif
> #else
> #error Invalid PTTYPE value
> #endif
> @@ -80,6 +96,10 @@ static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl)
> return (gpte & PT_LVL_ADDR_MASK(lvl)) >> PAGE_SHIFT;
> }
>
> +#if PTTYPE != PTTYPE_EPT
> +/*
> + * Comment out this for EPT because update_accessed_dirty_bits() is not used.
> + */
> static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> pt_element_t __user *ptep_user, unsigned index,
> pt_element_t orig_pte, pt_element_t new_pte)
> @@ -102,6 +122,7 @@ static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
>
> return (ret != orig_pte);
> }
> +#endif
>
> static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu,
> struct kvm_mmu_page *sp, u64 *spte,
> @@ -126,13 +147,21 @@ no_present:
> static inline unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, u64 gpte)
> {
> unsigned access;
> -
> +#if PTTYPE == PTTYPE_EPT
> + access = (gpte & (VMX_EPT_READABLE_MASK | VMX_EPT_WRITABLE_MASK |
> + VMX_EPT_EXECUTABLE_MASK));
It seems wrong. The ACC_XXX definition:
#define ACC_EXEC_MASK 1
#define ACC_WRITE_MASK PT_WRITABLE_MASK
#define ACC_USER_MASK PT_USER_MASK
#define ACC_ALL (ACC_EXEC_MASK | ACC_WRITE_MASK | ACC_USER_MASK)
The bits are different with the bits used in EPT page table, for example,
your code always see that the execution is not allowed.
> +#else
> access = (gpte & (PT_WRITABLE_MASK | PT_USER_MASK)) | ACC_EXEC_MASK;
> access &= ~(gpte >> PT64_NX_SHIFT);
> +#endif
>
> return access;
> }
>
> +#if PTTYPE != PTTYPE_EPT
> +/*
> + * EPT A/D bit support is not implemented.
> + */
> static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
> struct kvm_mmu *mmu,
> struct guest_walker *walker,
> @@ -169,6 +198,7 @@ static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
> }
> return 0;
> }
> +#endif
>
> /*
> * Fetch a guest pte for a guest virtual address
> @@ -177,7 +207,6 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
> struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> gva_t addr, u32 access)
> {
> - int ret;
> pt_element_t pte;
> pt_element_t __user *uninitialized_var(ptep_user);
> gfn_t table_gfn;
> @@ -192,7 +221,9 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
> gfn_t gfn;
>
> trace_kvm_mmu_pagetable_walk(addr, access);
> +#if PTTYPE != PTTYPE_EPT
> retry_walk:
> +#endif
> walker->level = mmu->root_level;
> pte = mmu->get_cr3(vcpu);
>
> @@ -277,6 +308,7 @@ retry_walk:
>
> walker->gfn = real_gpa >> PAGE_SHIFT;
>
> +#if PTTYPE != PTTYPE_EPT
> if (!write_fault)
> protect_clean_gpte(&pte_access, pte);
> else
> @@ -287,12 +319,15 @@ retry_walk:
> accessed_dirty &= pte >> (PT_DIRTY_SHIFT - PT_ACCESSED_SHIFT);
>
> if (unlikely(!accessed_dirty)) {
> + int ret;
> +
> ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker, write_fault);
> if (unlikely(ret < 0))
> goto error;
> else if (ret)
> goto retry_walk;
> }
> +#endif
There are lots of code in paging_tmpl.h depends on PT_ACCESSED_MASK/PT_DIRTY_MASK.
I do not see other parts are adjusted in your patch.
How about redefine PT_ACCESSED_MASK / PT_DIRTY_MASK, something like:
#if PTTYPE == 32
PT_ACCESS = PT_ACCESSED_MASK;
......
#elif PTTYPE == 64
PT_ACCESS = PT_ACCESSED_MASK;
......
#elif PTTYPE == PTTYPE_EPT
PT_ACCESS = 0
#else
.......
I guess the compiler can drop the unnecessary branch when PT_ACCESS == 0.
Also, it can help use to remove the untidy "#if PTTYPE != PTTYPE_EPT"
>
> walker->pt_access = pt_access;
> walker->pte_access = pte_access;
> @@ -323,6 +358,7 @@ 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)
> @@ -330,6 +366,7 @@ 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,
> @@ -754,6 +791,7 @@ 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)
> @@ -772,6 +810,7 @@ static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gva_t vaddr,
>
> return gpa;
> }
> +#endif
Strange!
Why does nested ept not need these functions? How to emulate the instruction faulted on L2?
next prev parent reply other threads:[~2013-05-21 7:52 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-19 4:52 [PATCH v3 01/13] nEPT: Support LOAD_IA32_EFER entry/exit controls for L1 Jun Nakajima
2013-05-19 4:52 ` [PATCH v3 02/13] nEPT: Move gpte_access() and prefetch_invalid_gpte() to paging_tmpl.h Jun Nakajima
2013-05-20 12:34 ` Paolo Bonzini
2013-05-19 4:52 ` [PATCH v3 03/13] nEPT: Add EPT tables support " Jun Nakajima
2013-05-21 7:52 ` Xiao Guangrong [this message]
2013-05-21 8:30 ` Xiao Guangrong
2013-05-21 9:01 ` Gleb Natapov
2013-05-21 11:05 ` Xiao Guangrong
2013-05-21 22:26 ` Nakajima, Jun
2013-05-22 1:10 ` Xiao Guangrong
2013-05-22 6:16 ` Gleb Natapov
2013-06-11 11:32 ` Gleb Natapov
2013-06-17 12:11 ` Xiao Guangrong
2013-06-18 10:57 ` Gleb Natapov
2013-06-18 12:51 ` Xiao Guangrong
2013-06-18 13:01 ` Gleb Natapov
2013-05-19 4:52 ` [PATCH v3 04/13] nEPT: Define EPT-specific link_shadow_page() Jun Nakajima
2013-05-20 12:43 ` Paolo Bonzini
2013-05-21 8:15 ` Xiao Guangrong
2013-05-21 21:44 ` Nakajima, Jun
2013-05-19 4:52 ` [PATCH v3 05/13] nEPT: MMU context for nested EPT Jun Nakajima
2013-05-21 8:50 ` Xiao Guangrong
2013-05-21 22:30 ` Nakajima, Jun
2013-05-19 4:52 ` [PATCH v3 06/13] nEPT: Fix cr3 handling in nested exit and entry Jun Nakajima
2013-05-20 13:19 ` Paolo Bonzini
2013-06-12 12:42 ` Gleb Natapov
2013-05-19 4:52 ` [PATCH v3 07/13] nEPT: Fix wrong test in kvm_set_cr3 Jun Nakajima
2013-05-20 13:17 ` Paolo Bonzini
2013-05-19 4:52 ` [PATCH v3 08/13] nEPT: Some additional comments Jun Nakajima
2013-05-20 13:21 ` Paolo Bonzini
2013-05-19 4:52 ` [PATCH v3 09/13] nEPT: Advertise EPT to L1 Jun Nakajima
2013-05-20 13:05 ` Paolo Bonzini
2013-05-19 4:52 ` [PATCH v3 10/13] nEPT: Nested INVEPT Jun Nakajima
2013-05-20 12:46 ` Paolo Bonzini
2013-05-21 9:16 ` Xiao Guangrong
2013-05-19 4:52 ` [PATCH v3 11/13] nEPT: Miscelleneous cleanups Jun Nakajima
2013-05-19 4:52 ` [PATCH v3 12/13] nEPT: Move is_rsvd_bits_set() to paging_tmpl.h Jun Nakajima
2013-05-19 4:52 ` [PATCH v3 13/13] nEPT: Inject EPT violation/misconfigration Jun Nakajima
2013-05-20 13:09 ` Paolo Bonzini
2013-05-21 10:56 ` Xiao Guangrong
2013-05-20 12:33 ` [PATCH v3 01/13] nEPT: Support LOAD_IA32_EFER entry/exit controls for L1 Paolo Bonzini
2013-07-02 3:01 ` Zhang, Yang Z
2013-07-02 13:59 ` Gleb Natapov
2013-07-02 14:28 ` Jan Kiszka
2013-07-02 15:15 ` Gleb Natapov
2013-07-02 15:34 ` Jan Kiszka
2013-07-02 15:43 ` Gleb Natapov
2013-07-04 8:42 ` Zhang, Yang Z
2013-07-08 12:37 ` Gleb Natapov
2013-07-08 14:28 ` Zhang, Yang Z
2013-07-08 16:08 ` Gleb Natapov
-- strict thread matches above, loose matches on Subject: below --
2013-05-09 0:53 Jun Nakajima
2013-05-09 0:53 ` [PATCH v3 02/13] nEPT: Move gpte_access() and prefetch_invalid_gpte() to paging_tmpl.h Jun Nakajima
2013-05-09 0:53 ` [PATCH v3 03/13] nEPT: Add EPT tables support " Jun Nakajima
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