From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 2/5] KVM: Implement CR read caching for KVM paravirt_ops Date: Mon, 18 Jun 2007 11:11:33 +0300 Message-ID: <46763E35.8020108@qumranet.com> References: <4675F462.1010708@codemonkey.ws> <4675F4F1.5090207@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4675F4F1.5090207-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Anthony Liguori Cc: kvm-devel , virtualization List-Id: virtualization@lists.linuxfoundation.org Anthony Liguori wrote: > +/* > + * Control register reads can be trapped. Since trapping is relatively > + * expensive, we can avoid paying the cost by caching logically. > + */ > +static unsigned long kvm_read_cr(int reg) > +{ > + struct kvm_paravirt_state *state > + = per_cpu(paravirt_state, smp_processor_id()); > + > + if (unlikely(!state->cr_valid[reg])) { > + if (reg == 0) > + state->cached_cr[reg] = native_read_cr0(); > + else if (reg == 3) > + state->cached_cr[reg] = native_read_cr3(); > + else if (reg == 4) > + state->cached_cr[reg] = native_read_cr4(); > + else > + BUG(); > + state->cr_valid[reg] = 1; > + } > + return state->cached_cr[reg]; > +} > + It would be good to declare this (and kvm_write_cr) always_inline. These functions are never called with a non-constant reg parameters, and the unsightly if tree (more readable as a switch, IMO) will fold nicely when inlined. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/