[PATCH 3.12 017/142] KVM: use slowpath for cross page cached accesses

Jiri Slaby
2015-05-16T08:30:40Z

From: Radim Krčmář <rkrcmar@redhat.com>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit ca3f0874723fad81d0c701b63ae3a17a408d5f25 upstream.

kvm_write_guest_cached() does not mark all written pages as dirty and
code comments in kvm_gfn_to_hva_cache_init() talk about NULL memslot
with cross page accesses. Fix all the easy way.

The check is '<= 1' to have the same result for 'len = 0' cache anywhere
in the page. (nr_pages_needed is 0 on page boundary.)

Fixes: 8f964525a121 ("KVM: Allow cross page reads and writes from cached translations.")
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Message-Id: <20150408121648.GA3519@potion.brq.redhat.com>
Reviewed-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
virt/kvm/kvm_main.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e068d0017fb8..a3510441f7d7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1540,8 +1540,8 @@ int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
ghc->generation = slots->generation;
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 = gfn_to_hva_many(ghc->memslot, start_gfn, NULL);
+ if (!kvm_is_error_hva(ghc->hva) && nr_pages_needed <= 1) {
ghc->hva += offset;
} else {
/*
--
2.3.7