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SubjectRe: [RFC PATCH 2/3] KVM: x86: use memory_prepare in fetch helper function
Il 06/05/2014 02:40, Bandan Das ha scritto:
> Insn fetch fastpath function. Not that
> arch.walk_mmu->gva_to_gpa can't be used but let's
> piggyback on top of interface meant for our purpose
>
> Signed-off-by: Bandan Das <bsd@redhat.com>
> ---
> arch/x86/kvm/x86.c | 25 +++++++++++++++++--------
> 1 file changed, 17 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 17e3d661..cf69e3b 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4065,29 +4065,38 @@ static int kvm_read_guest_virt_helper(gva_t addr, void *val, unsigned int bytes,
> struct x86_exception *exception)
> {
> void *data = val;
> - struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
> int r = X86EMUL_CONTINUE;
>
> while (bytes) {
> - gpa_t gpa = vcpu->arch.walk_mmu->gva_to_gpa(vcpu, addr, access,
> - exception);
> unsigned offset = addr & (PAGE_SIZE-1);
> unsigned toread = min(bytes, (unsigned)PAGE_SIZE - offset);
> int ret;
> + unsigned long uaddr;
>
> - if (gpa == UNMAPPED_GVA)
> - return X86EMUL_PROPAGATE_FAULT;
> - ret = kvm_read_guest(vcpu->kvm, gpa, data, toread);
> + ret = ctxt->ops->memory_prepare(ctxt, addr, toread,
> + exception, false,
> + NULL, &uaddr);

You can call the function from x86.c directly, no need to go through
ctxt->ops.

> + if (ret != X86EMUL_CONTINUE)
> + return ret;
> +
> + if (unlikely(kvm_is_error_hva(uaddr))) {
> + r = X86EMUL_PROPAGATE_FAULT;
> + return r;
> + }
> +
> + ret = __copy_from_user(data, (void __user *)uaddr, toread);
> if (ret < 0) {
> r = X86EMUL_IO_NEEDED;
> - goto out;
> + return r;
> }
>
> + ctxt->ops->memory_finish(ctxt, NULL, uaddr);

No need to call memory_finish, since you know the implementation
(perhaps add a comment).

Paolo

> bytes -= toread;
> data += toread;
> addr += toread;
> }
> -out:
> +
> return r;
> }
>
>



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