diff mbox

KVM: Allow cross page reads and writes from cached translations

Message ID alpine.DEB.2.02.1303282041300.2353@ahonig-virtual-machine (mailing list archive)
State New, archived
Headers show

Commit Message

Andrew Honig March 29, 2013, 3:44 a.m. UTC 
This patch adds support for kvm_gfn_to_hva_cache_init functions for
reads and writes that will cross a page.  If the range falls within
the same memslot, then this will be a fast operation.  If the range
is split between two memslots, then the slower kvm_read_guest and
kvm_write_guest are used.

Tested: Test against kvm_clock unit tests.

Signed-off-by: Andrew Honig <ahonig@google.com>
---
 arch/x86/kvm/lapic.c      |    2 +-
 arch/x86/kvm/x86.c        |   12 +++++-------
 include/linux/kvm_host.h  |    2 +-
 include/linux/kvm_types.h |    2 ++
 virt/kvm/kvm_main.c       |   43 +++++++++++++++++++++++++++++++++----------
 5 files changed, 42 insertions(+), 19 deletions(-)

Comments

Paolo Bonzini March 29, 2013, 8:34 a.m. UTC | #1 
Il 29/03/2013 04:44, Andrew Honig ha scritto:
> 
> This patch adds support for kvm_gfn_to_hva_cache_init functions for
> reads and writes that will cross a page.  If the range falls within
> the same memslot, then this will be a fast operation.  If the range
> is split between two memslots, then the slower kvm_read_guest and
> kvm_write_guest are used.
> 
> Tested: Test against kvm_clock unit tests.
> 
> Signed-off-by: Andrew Honig <ahonig@google.com>
> ---
>  arch/x86/kvm/lapic.c      |    2 +-
>  arch/x86/kvm/x86.c        |   12 +++++-------
>  include/linux/kvm_host.h  |    2 +-
>  include/linux/kvm_types.h |    2 ++
>  virt/kvm/kvm_main.c       |   43 +++++++++++++++++++++++++++++++++----------
>  5 files changed, 42 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 02b51dd..f77df1c 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1857,7 +1857,7 @@ int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64 data)
>  	if (!pv_eoi_enabled(vcpu))
>  		return 0;
>  	return kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.pv_eoi.data,
> -					 addr);
> +					 addr, sizeof(u8));
>  }
>  
>  void kvm_lapic_init(void)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f19ac0a..0fd5ad8 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1823,7 +1823,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
>  		return 0;
>  	}
>  
> -	if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa))
> +	if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa, 4))
>  		return 1;

Please use sizeof(u32).

>  	vcpu->arch.apf.send_user_only = !(data & KVM_ASYNC_PF_SEND_ALWAYS);
> @@ -1952,12 +1952,9 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  
>  		gpa_offset = data & ~(PAGE_MASK | 1);
>  
> -		/* Check that the address is 32-byte aligned. */
> -		if (gpa_offset & (sizeof(struct pvclock_vcpu_time_info) - 1))
> -			break;
> -
>  		if (kvm_gfn_to_hva_cache_init(vcpu->kvm,
> -		     &vcpu->arch.pv_time, data & ~1ULL))
> +		     &vcpu->arch.pv_time, data & ~1ULL,
> +		     sizeof(struct pvclock_vcpu_time_info)))
>  			vcpu->arch.pv_time_enabled = false;
>  		else
>  			vcpu->arch.pv_time_enabled = true;
> @@ -1977,7 +1974,8 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
>  			return 1;
>  
>  		if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.st.stime,
> -							data & KVM_STEAL_VALID_BITS))
> +						data & KVM_STEAL_VALID_BITS,
> +						sizeof(struct kvm_steal_time)))
>  			return 1;
>  
>  		vcpu->arch.st.msr_val = data;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index cad77fe..c139582 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -518,7 +518,7 @@ int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
>  int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>  			   void *data, unsigned long len);
>  int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
> -			      gpa_t gpa);
> +			      gpa_t gpa, unsigned long len);
>  int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
>  int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len);
>  struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
> diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
> index fa7cc72..bd420d6 100644
> --- a/include/linux/kvm_types.h
> +++ b/include/linux/kvm_types.h
> @@ -71,6 +71,8 @@ struct gfn_to_hva_cache {
>  	u64 generation;
>  	gpa_t gpa;
>  	unsigned long hva;
> +	unsigned long len;
> +	int slow;

You can just use memslot = NULL instead of the new member "slow".

>  	struct kvm_memory_slot *memslot;
>  };
>  
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index adc68fe..dcd3e57 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1541,21 +1541,38 @@ int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
>  }
>  
>  int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
> -			      gpa_t gpa)
> +			      gpa_t gpa, unsigned long len)
>  {
>  	struct kvm_memslots *slots = kvm_memslots(kvm);
>  	int offset = offset_in_page(gpa);
> -	gfn_t gfn = gpa >> PAGE_SHIFT;
> +	gfn_t start_gfn = gpa >> PAGE_SHIFT;
> +	gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT;
> +	gfn_t nr_pages_needed = end_gfn - start_gfn + 1;
> +	gfn_t nr_pages_avail;
>  
>  	ghc->gpa = gpa;
> +	ghc->slow = 0;
>  	ghc->generation = slots->generation;
> -	ghc->memslot = gfn_to_memslot(kvm, gfn);
> -	ghc->hva = gfn_to_hva_many(ghc->memslot, gfn, NULL);
> -	if (!kvm_is_error_hva(ghc->hva))
> +	ghc->len = len;
> +	ghc->memslot = gfn_to_memslot(kvm, start_gfn);
> +	ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn, &nr_pages_avail);
> +	if (!kvm_is_error_hva(ghc->hva) && nr_pages_avail >= nr_pages_needed) {
>  		ghc->hva += offset;
> -	else
> -		return -EFAULT;
> -
> +	} else {
> +		ghc->slow = 1;
> +		/*
> +		 * If the requested region crosses two memslots, we still
> +		 * verify that the entire region is valid here. 
> +		 */
> +		while (start_gfn <= end_gfn) {
> +			ghc->memslot = gfn_to_memslot(kvm, start_gfn);
> +			ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn,
> +						   &nr_pages_avail);
> +			if (kvm_is_error_hva(ghc->hva))
> +				return -EFAULT;
> +			start_gfn += nr_pages_avail;
> +		}
> +	}
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(kvm_gfn_to_hva_cache_init);
> @@ -1567,7 +1584,10 @@ int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>  	int r;

I think you want a

  BUG_ON(len > ghc->len);

here and in kvm_read_guest_cached.

Thanks,

Paolo

>  	if (slots->generation != ghc->generation)
> -		kvm_gfn_to_hva_cache_init(kvm, ghc, ghc->gpa);
> +		kvm_gfn_to_hva_cache_init(kvm, ghc, ghc->gpa, ghc->len);
> +
> +	if (unlikely(ghc->slow))
> +		return kvm_write_guest(kvm, ghc->gpa, data, len);
>  
>  	if (kvm_is_error_hva(ghc->hva))
>  		return -EFAULT;
> @@ -1588,7 +1608,10 @@ int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>  	int r;
>  
>  	if (slots->generation != ghc->generation)
> -		kvm_gfn_to_hva_cache_init(kvm, ghc, ghc->gpa);
> +		kvm_gfn_to_hva_cache_init(kvm, ghc, ghc->gpa, ghc->len);
> +
> +	if (unlikely(ghc->slow))
> +		return kvm_read_guest(kvm, ghc->gpa, data, len);
>  
>  	if (kvm_is_error_hva(ghc->hva))
>  		return -EFAULT;
> 

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diff mbox

Patch

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 02b51dd..f77df1c 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1857,7 +1857,7 @@  int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64 data)
 	if (!pv_eoi_enabled(vcpu))
 		return 0;
 	return kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.pv_eoi.data,
-					 addr);
+					 addr, sizeof(u8));
 }
 
 void kvm_lapic_init(void)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f19ac0a..0fd5ad8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1823,7 +1823,7 @@  static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
 		return 0;
 	}
 
-	if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa))
+	if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa, 4))
 		return 1;
 
 	vcpu->arch.apf.send_user_only = !(data & KVM_ASYNC_PF_SEND_ALWAYS);
@@ -1952,12 +1952,9 @@  int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 
 		gpa_offset = data & ~(PAGE_MASK | 1);
 
-		/* Check that the address is 32-byte aligned. */
-		if (gpa_offset & (sizeof(struct pvclock_vcpu_time_info) - 1))
-			break;
-
 		if (kvm_gfn_to_hva_cache_init(vcpu->kvm,
-		     &vcpu->arch.pv_time, data & ~1ULL))
+		     &vcpu->arch.pv_time, data & ~1ULL,
+		     sizeof(struct pvclock_vcpu_time_info)))
 			vcpu->arch.pv_time_enabled = false;
 		else
 			vcpu->arch.pv_time_enabled = true;
@@ -1977,7 +1974,8 @@  int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			return 1;
 
 		if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.st.stime,
-							data & KVM_STEAL_VALID_BITS))
+						data & KVM_STEAL_VALID_BITS,
+						sizeof(struct kvm_steal_time)))
 			return 1;
 
 		vcpu->arch.st.msr_val = data;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index cad77fe..c139582 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -518,7 +518,7 @@  int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
 int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
 			   void *data, unsigned long len);
 int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
-			      gpa_t gpa);
+			      gpa_t gpa, unsigned long len);
 int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
 int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len);
 struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
index fa7cc72..bd420d6 100644
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -71,6 +71,8 @@  struct gfn_to_hva_cache {
 	u64 generation;
 	gpa_t gpa;
 	unsigned long hva;
+	unsigned long len;
+	int slow;
 	struct kvm_memory_slot *memslot;
 };
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index adc68fe..dcd3e57 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1541,21 +1541,38 @@  int kvm_write_guest(struct kvm *kvm, gpa_t gpa, const void *data,
 }
 
 int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
-			      gpa_t gpa)
+			      gpa_t gpa, unsigned long len)
 {
 	struct kvm_memslots *slots = kvm_memslots(kvm);
 	int offset = offset_in_page(gpa);
-	gfn_t gfn = gpa >> PAGE_SHIFT;
+	gfn_t start_gfn = gpa >> PAGE_SHIFT;
+	gfn_t end_gfn = (gpa + len - 1) >> PAGE_SHIFT;
+	gfn_t nr_pages_needed = end_gfn - start_gfn + 1;
+	gfn_t nr_pages_avail;
 
 	ghc->gpa = gpa;
+	ghc->slow = 0;
 	ghc->generation = slots->generation;
-	ghc->memslot = gfn_to_memslot(kvm, gfn);
-	ghc->hva = gfn_to_hva_many(ghc->memslot, gfn, NULL);
-	if (!kvm_is_error_hva(ghc->hva))
+	ghc->len = len;
+	ghc->memslot = gfn_to_memslot(kvm, start_gfn);
+	ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn, &nr_pages_avail);
+	if (!kvm_is_error_hva(ghc->hva) && nr_pages_avail >= nr_pages_needed) {
 		ghc->hva += offset;
-	else
-		return -EFAULT;
-
+	} else {
+		ghc->slow = 1;
+		/*
+		 * If the requested region crosses two memslots, we still
+		 * verify that the entire region is valid here. 
+		 */
+		while (start_gfn <= end_gfn) {
+			ghc->memslot = gfn_to_memslot(kvm, start_gfn);
+			ghc->hva = gfn_to_hva_many(ghc->memslot, start_gfn,
+						   &nr_pages_avail);
+			if (kvm_is_error_hva(ghc->hva))
+				return -EFAULT;
+			start_gfn += nr_pages_avail;
+		}
+	}
 	return 0;
 }
 EXPORT_SYMBOL_GPL(kvm_gfn_to_hva_cache_init);
@@ -1567,7 +1584,10 @@  int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
 	int r;
 
 	if (slots->generation != ghc->generation)
-		kvm_gfn_to_hva_cache_init(kvm, ghc, ghc->gpa);
+		kvm_gfn_to_hva_cache_init(kvm, ghc, ghc->gpa, ghc->len);
+
+	if (unlikely(ghc->slow))
+		return kvm_write_guest(kvm, ghc->gpa, data, len);
 
 	if (kvm_is_error_hva(ghc->hva))
 		return -EFAULT;
@@ -1588,7 +1608,10 @@  int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
 	int r;
 
 	if (slots->generation != ghc->generation)
-		kvm_gfn_to_hva_cache_init(kvm, ghc, ghc->gpa);
+		kvm_gfn_to_hva_cache_init(kvm, ghc, ghc->gpa, ghc->len);
+
+	if (unlikely(ghc->slow))
+		return kvm_read_guest(kvm, ghc->gpa, data, len);
 
 	if (kvm_is_error_hva(ghc->hva))
 		return -EFAULT;