From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Kardashevskiy Date: Tue, 19 Mar 2019 06:53:13 +0000 Subject: Re: [PATCH 1/3] KVM: PPC: Implement kvmppc_copy_guest() to perform in place copy of guest memory Message-Id: List-Id: References: <20190319040435.10716-1-sjitindarsingh@gmail.com> In-Reply-To: <20190319040435.10716-1-sjitindarsingh@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: kvm-ppc@vger.kernel.org On 19/03/2019 15:04, Suraj Jitindar Singh wrote: > Implement the function kvmppc_copy_guest() to be used to perform a memory > copy from one guest physical address to another of a variable length. > > This performs similar functionality as the kvm_read_guest() and > kvm_write_guest() functions, except both addresses point to guest memory. > This performs a copy in place using raw_copy_in_user() to avoid having to > buffer the data. > > The guest memory can reside in different memslots and the copy length > can span memslots. > > Signed-off-by: Suraj Jitindar Singh > --- > arch/powerpc/kvm/book3s_hv.c | 69 ++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 69 insertions(+) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index ec38576dc685..7179ea783f4f 100644 > --- a/arch/powerpc/kvm/book3s_hv.c > +++ b/arch/powerpc/kvm/book3s_hv.c > @@ -814,6 +814,75 @@ static int kvmppc_h_set_mode(struct kvm_vcpu *vcpu, unsigned long mflags, > } > } > > +static int __kvmppc_copy_guest_page(struct kvm_memory_slot *to_memslot, > + gfn_t to_gfn, int to_offset, > + struct kvm_memory_slot *from_memslot, > + gfn_t from_gfn, int from_offset, int len) > +{ > + int r; > + unsigned long to_addr, from_addr; > + > + to_addr = gfn_to_hva_memslot(to_memslot, to_gfn); > + if (kvm_is_error_hva(to_addr)) > + return -EFAULT; > + from_addr = gfn_to_hva_memslot(from_memslot, from_gfn); > + if (kvm_is_error_hva(from_addr)) > + return -EFAULT; > + r = raw_copy_in_user((void __user *)to_addr + to_offset, > + (void __user *)from_addr + from_offset, len); > + if (r) > + return -EFAULT; > + return 0; > +} > + > +static int next_segment_many(unsigned long len, int offset1, int offset2) What is the "_many" suffix about? > +{ > + int size = min(PAGE_SIZE - offset1, PAGE_SIZE - offset2); Nitpicking :) Here it is min()... > + > + if (len > size) > + return size; > + else > + return len; ...but here it is if() when it could also be min() (or may be min_t()). > +} > + > +static int kvmppc_copy_guest(struct kvm *kvm, gpa_t to, gpa_t from, > + unsigned long len) This does not compile (most comments are made just because I had to reply anyway): /home/aik/p/kernel/arch/powerpc/kvm/book3s_hv.c:835:12: error: ‘kvmppc_copy_guest’ defined but not used [-Werror=unused-function] static int kvmppc_copy_guest(struct kvm *kvm, gpa_t to, gpa_t from, ^~~~~~~~~~~~~~~~~ imho 1/3 and 2/3 should be one patch. A general comment is that the H_PAGE_INIT hcall description says "The logical addresses ... must both point to the start of a 4 K system memory page" so the loop will never have to execute more than once, cannot span memslots => it could be lot simpler then, or I missed something here (unlikely, after reading 3/3). > +{ > + struct kvm_memory_slot *to_memslot = NULL; > + struct kvm_memory_slot *from_memslot = NULL; > + gfn_t to_gfn = to >> PAGE_SHIFT; > + gfn_t from_gfn = from >> PAGE_SHIFT; > + int seg; > + int to_offset = offset_in_page(to); > + int from_offset = offset_in_page(from); > + int ret; > + > + while ((seg = next_segment_many(len, to_offset, from_offset)) != 0) { > + if (!to_memslot || (to_gfn >= (to_memslot->base_gfn + > + to_memslot->npages))) > + to_memslot = gfn_to_memslot(kvm, to_gfn); > + if (!from_memslot || (from_gfn >= (from_memslot->base_gfn + > + from_memslot->npages))) > + from_memslot = gfn_to_memslot(kvm, from_gfn); > + > + ret = __kvmppc_copy_guest_page(to_memslot, to_gfn, to_offset, > + from_memslot, from_gfn, > + from_offset, seg); > + if (ret < 0) > + return ret; > + mark_page_dirty(kvm, to_gfn); Nit: if you made mark_page_dirty_in_slot() public (yeah it is in the common code), you could save here one search through memslots. > + > + to_offset = (to_offset + seg) & (PAGE_SIZE - 1); s/(PAGE_SIZE - 1)/~PAGE_MASK/ ? Or even use again that offset_in_page() as you did above? > + from_offset = (from_offset + seg) & (PAGE_SIZE - 1); > + len -= seg; > + if (!to_offset) > + to_gfn += 1; > + if (!from_offset) > + from_gfn += 1; > + } > + return 0; > +} > + > static int kvm_arch_vcpu_yield_to(struct kvm_vcpu *target) > { > struct kvmppc_vcore *vcore = target->arch.vcore; > -- Alexey