From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 1/1] Enble a guest to access a device's memory mapped I/O regions directly. Date: Fri, 18 Apr 2008 18:50:03 +0300 Message-ID: <4808C32B.2030307@qumranet.com> References: <1208352331-27201-1-git-send-email-benami@il.ibm.com> <1208352331-27201-2-git-send-email-benami@il.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net, andrea@qumranet.com, allen.m.kay@intel.com To: benami@il.ibm.com Return-path: In-Reply-To: <1208352331-27201-2-git-send-email-benami@il.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org benami@il.ibm.com wrote: > From: Ben-Ami Yassour > > Signed-off-by: Ben-Ami Yassour > Signed-off-by: Muli Ben-Yehuda > --- > arch/x86/kvm/mmu.c | 59 +++++++++++++++++++++++++++++-------------- > arch/x86/kvm/paging_tmpl.h | 19 +++++++++---- > include/linux/kvm_host.h | 2 +- > virt/kvm/kvm_main.c | 17 +++++++++++- > 4 files changed, 69 insertions(+), 28 deletions(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 078a7f1..c89029d 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -112,6 +112,8 @@ static int dbg = 1; > #define PT_FIRST_AVAIL_BITS_SHIFT 9 > #define PT64_SECOND_AVAIL_BITS_SHIFT 52 > > +#define PT_SHADOW_IO_MARK (1ULL << PT_FIRST_AVAIL_BITS_SHIFT) > + > Please rename this PT_SHADOW_MMIO_MASK. > #define VALID_PAGE(x) ((x) != INVALID_PAGE) > > #define PT64_LEVEL_BITS 9 > @@ -237,6 +239,9 @@ static int is_dirty_pte(unsigned long pte) > > static int is_rmap_pte(u64 pte) > { > + if (pte & PT_SHADOW_IO_MARK) > + return false; > + > return is_shadow_present_pte(pte); > } > Why avoid rmap on mmio pages? Sure it's unnecessary work, but having less cases improves overall reliability. You can use pfn_valid() in gfn_to_pfn() and kvm_release_pfn_*() to conditionally update the page refcounts. -- Any sufficiently difficult bug is indistinguishable from a feature. ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone