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Message-Id: <20130423215457.356345907@linuxfoundation.org>
Date: Tue, 23 Apr 2013 14:56:17 -0700
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Andrew Honig <ahonig@...gle.com>,
Gleb Natapov <gleb@...hat.com>,
Ben Hutchings <ben@...adent.org.uk>
Subject: [ 10/23] KVM: Allow cross page reads and writes from cached translations.
3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Andrew Honig <ahonig@...gle.com>
commit 8f964525a121f2ff2df948dac908dcc65be21b5b upstream.
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@...gle.com>
Signed-off-by: Gleb Natapov <gleb@...hat.com>
Cc: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
arch/x86/kvm/x86.c | 10 ++++------
include/linux/kvm_host.h | 2 +-
include/linux/kvm_types.h | 1 +
virt/kvm/kvm_main.c | 39 +++++++++++++++++++++++++++++++--------
4 files changed, 37 insertions(+), 15 deletions(-)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1448,7 +1448,8 @@ static int kvm_pv_enable_async_pf(struct
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);
@@ -1530,12 +1531,9 @@ int kvm_set_msr_common(struct kvm_vcpu *
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;
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -388,7 +388,7 @@ int kvm_write_guest(struct kvm *kvm, gpa
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);
--- a/include/linux/kvm_types.h
+++ b/include/linux/kvm_types.h
@@ -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;
};
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1375,20 +1375,38 @@ int kvm_write_guest(struct kvm *kvm, gpa
}
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(slots, 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 {
+ /*
+ * 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;
}
@@ -1400,8 +1418,13 @@ int kvm_write_guest_cached(struct kvm *k
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;
--
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