From mboxrd@z Thu Jan 1 00:00:00 1970 From: julien.grall@linaro.org (Julien Grall) Date: Fri, 01 Aug 2014 17:53:39 +0100 Subject: [Xen-devel] [PATCH v3 1/3] xen/arm: introduce XENFEAT_grant_map_identity In-Reply-To: <1406904984-16068-1-git-send-email-stefano.stabellini@eu.citrix.com> References: <1406904984-16068-1-git-send-email-stefano.stabellini@eu.citrix.com> Message-ID: <53DBC613.4070506@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Stefano, On 01/08/14 15:56, Stefano Stabellini wrote: > The flag tells us that the hypervisor maps a grant page to guest > physical address == machine address of the page in addition to the > normal grant mapping address. It is needed to properly issue cache > maintenance operation at the completion of a DMA operation involving a > foreign grant. > > Signed-off-by: Stefano Stabellini > Tested-by: Denis Schneider > > --- > Changes in v3: > - rename XENFEAT_grant_map_11 to XENFEAT_grant_map_identity. > --- > arch/arm/xen/enlighten.c | 6 ++++++ > include/xen/interface/features.h | 3 +++ > 2 files changed, 9 insertions(+) > > diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c > index b96723e..eef324f 100644 > --- a/arch/arm/xen/enlighten.c > +++ b/arch/arm/xen/enlighten.c > @@ -262,6 +262,12 @@ static int __init xen_guest_init(void) > xen_domain_type = XEN_HVM_DOMAIN; > > xen_setup_features(); > + > + if (!xen_feature(XENFEAT_grant_map_identity)) { > + pr_warn("Please upgrade your Xen.\n" > + "If your platform has any non-coherent DMA devices, they won't work properly.\n"); > + } I know we talked about this on a previous thread but I can't find it in my mail :/ Does a Linux with this series will work on Xen 4.4? If not what's the plan? I think we have to keep any OS working on top on Xen 4.4 as people may want to retrieve the latest kernel for drivers bug fixes... For running a previous kernel on Xen 4.5, then it will still be buggy. It might be worse to backport thise series on LTS kernel (i.e at least 3.14). Regards, -- Julien Grall