From c471da1e3f5c6e43397dccf47cefd8edc86aa9f0 Mon Sep 17 00:00:00 2001 From: Andrew Honig Date: Fri, 29 Mar 2013 09:35:21 -0700 Subject: KVM: Allow cross page reads and writes from cached translations. 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 Signed-off-by: Gleb Natapov [bwh: Backported to 3.2: - Drop change in lapic.c - Keep using __gfn_to_memslot() in kvm_gfn_to_hva_cache_init()] Signed-off-by: Ben Hutchings --- virt/kvm/kvm_main.c | 47 +++++++++++++++++++++++++++++++++++++---------- 1 file changed, 37 insertions(+), 10 deletions(-) (limited to 'virt') diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index ec747dc..8bf05f0 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1401,21 +1401,38 @@ 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(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(slots, 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(slots, 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); @@ -1426,8 +1443,13 @@ 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; @@ -1447,8 +1469,13 @@ 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; -- cgit v1.1