From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCH] tools/libxc: Avoid hypercalls for cacheflush on x86 Date: Mon, 3 Mar 2014 16:19:58 +0000 Message-ID: <5314ABAE.1050109@citrix.com> References: <1393857478-14993-1-git-send-email-andrew.cooper3@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1393857478-14993-1-git-send-email-andrew.cooper3@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper Cc: Ian Jackson , Ian Campbell , Xen-devel List-Id: xen-devel@lists.xenproject.org On 03/03/14 14:37, Andrew Cooper wrote: > XEN_DOMCTL_cacheflush hypercalls are -ENOSYS on x86. As domain > creation/migration is already very hypercall-heavy, avoid making extra > redundant hypercalls > > Signed-off-by: Andrew Cooper > CC: Ian Campbell > CC: Ian Jackson > > --- > > Discovered when running valgrind against XenServer trunk, which is now 4.4 > based. > --- > tools/libxc/xc_domain.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/tools/libxc/xc_domain.c b/tools/libxc/xc_domain.c > index 369c3f3..b9cc1db 100644 > --- a/tools/libxc/xc_domain.c > +++ b/tools/libxc/xc_domain.c > @@ -51,12 +51,18 @@ int xc_domain_create(xc_interface *xch, > int xc_domain_cacheflush(xc_interface *xch, uint32_t domid, > xen_pfn_t start_pfn, xen_pfn_t nr_pfns) > { > +#if defined (__i386__) || defined (__x86_64__) > + /* This is not implemented or needed for x86. Avoid repeatedly going to > + * Xen to find -ENOSYS. */ > + return -ENOSYS; > +#else > DECLARE_DOMCTL; > domctl.cmd = XEN_DOMCTL_cacheflush; > domctl.domain = (domid_t)domid; > domctl.u.cacheflush.start_pfn = start_pfn; > domctl.u.cacheflush.nr_pfns = nr_pfns; > return do_domctl(xch, &domctl); > +#endif Rather than icky #ifdef's I suggest caching the result of any -ENOSYS return value. David