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KVM: Allow cross page reads and writes from cached translations.

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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>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
This commit is contained in:
Andrew Honig 2013-03-29 09:35:21 -07:00 • committed by Gleb Natapov
commit 8f964525a1
5 changed files with 46 additions and 19 deletions
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2
arch/x86/kvm/lapic.c
View file

@ -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)

13
arch/x86/kvm/x86.c
View file

@ -1823,7 +1823,8 @@ 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,
sizeof(u32)))
return 1;
vcpu->arch.apf.send_user_only = !(data & KVM_ASYNC_PF_SEND_ALWAYS);
@ -1952,12 +1953,9 @@ 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 +1975,8 @@ 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;

2
include/linux/kvm_host.h
View file

@ -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);

1
include/linux/kvm_types.h
View file

@ -71,6 +71,7 @@ struct gfn_to_hva_cache {
u64 generation;
gpa_t gpa;
unsigned long hva;
unsigned long len;
struct kvm_memory_slot *memslot;
};

45
virt/kvm/kvm_main.c
View file

@ -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->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
} else {
/*
* 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;
}
/* Use the slow path for cross page reads and writes. */
ghc->memslot = NULL;
}
return 0;
}
EXPORT_SYMBOL_GPL(kvm_gfn_to_hva_cache_init);
@ -1566,8 +1583,13 @@ int kvm_write_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
struct kvm_memslots *slots = kvm_memslots(kvm);
int r;
BUG_ON(len > ghc->len);
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->memslot))
return kvm_write_guest(kvm, ghc->gpa, data, len);
if (kvm_is_error_hva(ghc->hva))
return -EFAULT;
@ -1587,8 +1609,13 @@ int kvm_read_guest_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
struct kvm_memslots *slots = kvm_memslots(kvm);
int r;
BUG_ON(len > ghc->len);
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->memslot))
return kvm_read_guest(kvm, ghc->gpa, data, len);
if (kvm_is_error_hva(ghc->hva))
return -EFAULT;