* [PATCH] KVM: Allow cross page reads and writes from cached translations
@ 2013-03-29 3:44 Andrew Honig
2013-03-29 8:34 ` Paolo Bonzini
0 siblings, 1 reply; 2+ messages in thread
From: Andrew Honig @ 2013-03-29 3:44 UTC (permalink / raw)
To: kvm; +Cc: ahonig
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;
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;
--
1.7.10.4
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] KVM: Allow cross page reads and writes from cached translations
2013-03-29 3:44 [PATCH] KVM: Allow cross page reads and writes from cached translations Andrew Honig
@ 2013-03-29 8:34 ` Paolo Bonzini
0 siblings, 0 replies; 2+ messages in thread
From: Paolo Bonzini @ 2013-03-29 8:34 UTC (permalink / raw)
To: Andrew Honig; +Cc: kvm
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;
>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2013-03-29 3:44 [PATCH] KVM: Allow cross page reads and writes from cached translations Andrew Honig
2013-03-29 8:34 ` Paolo Bonzini
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