[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2 1/3] xen/arm: introduce XENFEAT_grant_map_11
On Tue, 2014-07-08 at 16:54 +0100, Stefano Stabellini wrote: > On Tue, 8 Jul 2014, Ian Campbell wrote: > > On Tue, 2014-07-08 at 16:42 +0100, 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 <stefano.stabellini@xxxxxxxxxxxxx> > > > --- > > > 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..ee3135a 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_11)) { > > > + pr_warn("Please upgrade your Xen.\n" > > > + "If your platform has any non-coherent DMA > > > devices, they won't work properly.\n"); > > > + } > > > > Unfortunately this isn't quite complete. On a system where all devices > > are behind an SMMU then we would want to be able to disable the 1:1 > > workaround, which in turn would imply disabling this feature flag too > > (since it is no longer necessary and also impossible to implement in > > that case). > > That is true, but in such a system we would have to tell the kernel that > DMAing is safe, so this will turn into: Oh right, yes. Good then ;-) > > if (!xen_feature(XENFEAT_grant_map_11) && > !xen_feature(XENFEAT_safe_dma)) { > pr_warn("Please upgrade your Xen.\n" > "If your platform has any non-coherent DMA devices, > they won't work properly.\n"); > } _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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