diff mbox series

[2/7] KVM: x86/mmu: Replace hardcoded value 0 for the initial value for SPTE

Message ID 20240507154459.3950778-3-pbonzini@redhat.com (mailing list archive)
State New
Headers show
Series KVM: MMU changes for TDX VE support | expand

Commit Message

Paolo Bonzini May 7, 2024, 3:44 p.m. UTC 
From: Sean Christopherson <seanjc@google.com>

The TDX support will need the "suppress #VE" bit (bit 63) set as the
initial value for SPTE.  To reduce code change size, introduce a new macro
SHADOW_NONPRESENT_VALUE for the initial value for the shadow page table
entry (SPTE) and replace hard-coded value 0 for it.  Initialize shadow page
tables with their value.

The plan is to unconditionally set the "suppress #VE" bit for both AMD and
Intel as: 1) AMD hardware uses the bit 63 as NX for present SPTE and
ignored for non-present SPTE; 2) for conventional VMX guests, KVM never
enables the "EPT-violation #VE" in VMCS control and "suppress #VE" bit is
ignored by hardware.

No functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Message-Id: <acdf09bf60cad12c495005bf3495c54f6b3069c9.1705965635.git.isaku.yamahata@intel.com>
[Remove unnecessary CONFIG_X86_64 check. - Paolo]
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/mmu/mmu.c         | 14 +++++++++-----
 arch/x86/kvm/mmu/paging_tmpl.h |  2 +-
 arch/x86/kvm/mmu/spte.h        |  4 +++-
 arch/x86/kvm/mmu/tdp_mmu.c     | 12 ++++++------
 4 files changed, 19 insertions(+), 13 deletions(-)

Comments

Isaku Yamahata May 15, 2024, 5:32 p.m. UTC | #1 
On Tue, May 07, 2024 at 11:44:54AM -0400,
Paolo Bonzini <pbonzini@redhat.com> wrote:

> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index c6192a52bd31..f5401967897a 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -603,7 +603,7 @@ static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
>  	 * here since the SPTE is going from non-present to non-present.  Use
>  	 * the raw write helper to avoid an unnecessary check on volatile bits.
>  	 */
> -	__kvm_tdp_mmu_write_spte(iter->sptep, 0);
> +	__kvm_tdp_mmu_write_spte(iter->sptep, SHADOW_NONPRESENT_VALUE);
>  
>  	return 0;
>  }
> @@ -740,8 +740,8 @@ static void __tdp_mmu_zap_root(struct kvm *kvm, struct kvm_mmu_page *root,
>  			continue;
>  
>  		if (!shared)
> -			tdp_mmu_iter_set_spte(kvm, &iter, 0);
> -		else if (tdp_mmu_set_spte_atomic(kvm, &iter, 0))
> +			tdp_mmu_iter_set_spte(kvm, &iter, SHADOW_NONPRESENT_VALUE);
> +		else if (tdp_mmu_set_spte_atomic(kvm, &iter, SHADOW_NONPRESENT_VALUE))
>  			goto retry;
>  	}
>  }
> @@ -808,8 +808,8 @@ bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
>  	if (WARN_ON_ONCE(!is_shadow_present_pte(old_spte)))
>  		return false;
>  
> -	tdp_mmu_set_spte(kvm, kvm_mmu_page_as_id(sp), sp->ptep, old_spte, 0,
> -			 sp->gfn, sp->role.level + 1);
> +	tdp_mmu_set_spte(kvm, kvm_mmu_page_as_id(sp), sp->ptep, old_spte,
> +			 SHADOW_NONPRESENT_VALUE, sp->gfn, sp->role.level + 1);
>  
>  	return true;
>  }
> @@ -843,7 +843,7 @@ static bool tdp_mmu_zap_leafs(struct kvm *kvm, struct kvm_mmu_page *root,
>  		    !is_last_spte(iter.old_spte, iter.level))
>  			continue;
>  
> -		tdp_mmu_iter_set_spte(kvm, &iter, 0);
> +		tdp_mmu_iter_set_spte(kvm, &iter, SHADOW_NONPRESENT_VALUE);
>  
>  		/*
>  		 * Zappings SPTEs in invalid roots doesn't require a TLB flush,
> -- 
> 2.43.0

I missed one conversion.  Here is the fix.  I found this during reviewing
TDX TDP MMU changes at [1].

[1] https://lore.kernel.org/kvm/20240515005952.3410568-11-rick.p.edgecombe@intel.com/

Paolo, how do you want me to proceed? I can send a updated patch or you can
directly fix the patch in kvm-coco-queue.  I'm fine with either way.


From 7910130c0a3f2c5d814d6f14d663b4b692a2c7e4 Mon Sep 17 00:00:00 2001
Message-ID: <7910130c0a3f2c5d814d6f14d663b4b692a2c7e4.1715793643.git.isaku.yamahata@intel.com>
From: Isaku Yamahata <isaku.yamahata@intel.com>
Date: Wed, 15 May 2024 10:19:08 -0700
Subject: [PATCH] fixup! KVM: x86/mmu: Replace hardcoded value 0 for the
 initial value for SPTE

---
 arch/x86/kvm/mmu/tdp_mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 1259dd63defc..36539c1b36cd 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -626,7 +626,7 @@ static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
 	 * SPTEs.
 	 */
 	handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte,
-			    0, iter->level, true);
+			    SHADOW_NONPRESENT_VALUE, iter->level, true);
 
 	return 0;
 }

base-commit: 698ca1e403579ca00e16a5b28ae4d576d9f1b20e
Paolo Bonzini May 15, 2024, 5:33 p.m. UTC | #2 
On 5/15/24 19:32, Isaku Yamahata wrote:
> Paolo, how do you want me to proceed? I can send a updated patch or you can
> directly fix the patch in kvm-coco-queue.  I'm fine with either way.

I'll fix it, thanks!

Paolo

> From 7910130c0a3f2c5d814d6f14d663b4b692a2c7e4 Mon Sep 17 00:00:00 2001
> Message-ID:<7910130c0a3f2c5d814d6f14d663b4b692a2c7e4.1715793643.git.isaku.yamahata@intel.com>
> From: Isaku Yamahata<isaku.yamahata@intel.com>
> Date: Wed, 15 May 2024 10:19:08 -0700
> Subject: [PATCH] fixup! KVM: x86/mmu: Replace hardcoded value 0 for the
>   initial value for SPTE
> 
> ---
>   arch/x86/kvm/mmu/tdp_mmu.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index 1259dd63defc..36539c1b36cd 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -626,7 +626,7 @@ static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
>   	 * SPTEs.
>   	 */
>   	handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte,
> -			    0, iter->level, true);
> +			    SHADOW_NONPRESENT_VALUE, iter->level, true);
>   
>   	return 0;
>   }
> 
> base-commit: 698ca1e403579ca00e16a5b28ae4d576d9f1b20e
diff mbox series

Patch

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 08900a0563f9..fbfdc606f1f1 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -567,9 +567,9 @@  static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep)
 
 	if (!is_shadow_present_pte(old_spte) ||
 	    !spte_has_volatile_bits(old_spte))
-		__update_clear_spte_fast(sptep, 0ull);
+		__update_clear_spte_fast(sptep, SHADOW_NONPRESENT_VALUE);
 	else
-		old_spte = __update_clear_spte_slow(sptep, 0ull);
+		old_spte = __update_clear_spte_slow(sptep, SHADOW_NONPRESENT_VALUE);
 
 	if (!is_shadow_present_pte(old_spte))
 		return old_spte;
@@ -603,7 +603,7 @@  static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep)
  */
 static void mmu_spte_clear_no_track(u64 *sptep)
 {
-	__update_clear_spte_fast(sptep, 0ull);
+	__update_clear_spte_fast(sptep, SHADOW_NONPRESENT_VALUE);
 }
 
 static u64 mmu_spte_get_lockless(u64 *sptep)
@@ -1897,7 +1897,8 @@  static bool kvm_sync_page_check(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 
 static int kvm_sync_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int i)
 {
-	if (!sp->spt[i])
+	/* sp->spt[i] has initial value of shadow page table allocation */
+	if (sp->spt[i] == SHADOW_NONPRESENT_VALUE)
 		return 0;
 
 	return vcpu->arch.mmu->sync_spte(vcpu, sp, i);
@@ -6120,7 +6121,10 @@  int kvm_mmu_create(struct kvm_vcpu *vcpu)
 	vcpu->arch.mmu_page_header_cache.kmem_cache = mmu_page_header_cache;
 	vcpu->arch.mmu_page_header_cache.gfp_zero = __GFP_ZERO;
 
-	vcpu->arch.mmu_shadow_page_cache.gfp_zero = __GFP_ZERO;
+	vcpu->arch.mmu_shadow_page_cache.init_value =
+		SHADOW_NONPRESENT_VALUE;
+	if (!vcpu->arch.mmu_shadow_page_cache.init_value)
+		vcpu->arch.mmu_shadow_page_cache.gfp_zero = __GFP_ZERO;
 
 	vcpu->arch.mmu = &vcpu->arch.root_mmu;
 	vcpu->arch.walk_mmu = &vcpu->arch.root_mmu;
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 4d4e98fe4f35..bebd73cd61bb 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -911,7 +911,7 @@  static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int
 	gpa_t pte_gpa;
 	gfn_t gfn;
 
-	if (WARN_ON_ONCE(!sp->spt[i]))
+	if (WARN_ON_ONCE(sp->spt[i] == SHADOW_NONPRESENT_VALUE))
 		return 0;
 
 	first_pte_gpa = FNAME(get_level1_sp_gpa)(sp);
diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index f5c600c52f83..0f4ec2859474 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -149,6 +149,8 @@  static_assert(MMIO_SPTE_GEN_LOW_BITS == 8 && MMIO_SPTE_GEN_HIGH_BITS == 11);
 
 #define MMIO_SPTE_GEN_MASK		GENMASK_ULL(MMIO_SPTE_GEN_LOW_BITS + MMIO_SPTE_GEN_HIGH_BITS - 1, 0)
 
+#define SHADOW_NONPRESENT_VALUE	0ULL
+
 extern u64 __read_mostly shadow_host_writable_mask;
 extern u64 __read_mostly shadow_mmu_writable_mask;
 extern u64 __read_mostly shadow_nx_mask;
@@ -194,7 +196,7 @@  extern u64 __read_mostly shadow_nonpresent_or_rsvd_mask;
  *
  * Only used by the TDP MMU.
  */
-#define REMOVED_SPTE	0x5a0ULL
+#define REMOVED_SPTE	(SHADOW_NONPRESENT_VALUE | 0x5a0ULL)
 
 /* Removed SPTEs must not be misconstrued as shadow present PTEs. */
 static_assert(!(REMOVED_SPTE & SPTE_MMU_PRESENT_MASK));
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index c6192a52bd31..f5401967897a 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -603,7 +603,7 @@  static inline int tdp_mmu_zap_spte_atomic(struct kvm *kvm,
 	 * here since the SPTE is going from non-present to non-present.  Use
 	 * the raw write helper to avoid an unnecessary check on volatile bits.
 	 */
-	__kvm_tdp_mmu_write_spte(iter->sptep, 0);
+	__kvm_tdp_mmu_write_spte(iter->sptep, SHADOW_NONPRESENT_VALUE);
 
 	return 0;
 }
@@ -740,8 +740,8 @@  static void __tdp_mmu_zap_root(struct kvm *kvm, struct kvm_mmu_page *root,
 			continue;
 
 		if (!shared)
-			tdp_mmu_iter_set_spte(kvm, &iter, 0);
-		else if (tdp_mmu_set_spte_atomic(kvm, &iter, 0))
+			tdp_mmu_iter_set_spte(kvm, &iter, SHADOW_NONPRESENT_VALUE);
+		else if (tdp_mmu_set_spte_atomic(kvm, &iter, SHADOW_NONPRESENT_VALUE))
 			goto retry;
 	}
 }
@@ -808,8 +808,8 @@  bool kvm_tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
 	if (WARN_ON_ONCE(!is_shadow_present_pte(old_spte)))
 		return false;
 
-	tdp_mmu_set_spte(kvm, kvm_mmu_page_as_id(sp), sp->ptep, old_spte, 0,
-			 sp->gfn, sp->role.level + 1);
+	tdp_mmu_set_spte(kvm, kvm_mmu_page_as_id(sp), sp->ptep, old_spte,
+			 SHADOW_NONPRESENT_VALUE, sp->gfn, sp->role.level + 1);
 
 	return true;
 }
@@ -843,7 +843,7 @@  static bool tdp_mmu_zap_leafs(struct kvm *kvm, struct kvm_mmu_page *root,
 		    !is_last_spte(iter.old_spte, iter.level))
 			continue;
 
-		tdp_mmu_iter_set_spte(kvm, &iter, 0);
+		tdp_mmu_iter_set_spte(kvm, &iter, SHADOW_NONPRESENT_VALUE);
 
 		/*
 		 * Zappings SPTEs in invalid roots doesn't require a TLB flush,