From 5ebc77de83c7b74543de774afa7395b3b790e65e Mon Sep 17 00:00:00 2001 From: Stefano Stabellini Date: Wed, 10 Sep 2014 22:49:30 +0000 Subject: [PATCH] xen/arm: introduce XENFEAT_grant_map_identity 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 --- 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 98544c5f86e9..0e15f011f9c8 100644 --- a/arch/arm/xen/enlighten.c +++ b/arch/arm/xen/enlighten.c @@ -260,6 +260,12 @@ 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"); + } + if (xen_feature(XENFEAT_dom0)) xen_start_info->flags |= SIF_INITDOMAIN|SIF_PRIVILEGED; else diff --git a/include/xen/interface/features.h b/include/xen/interface/features.h index 131a6ccdba25..14334d0161d5 100644 --- a/include/xen/interface/features.h +++ b/include/xen/interface/features.h @@ -53,6 +53,9 @@ /* operation as Dom0 is supported */ #define XENFEAT_dom0 11 +/* Xen also maps grant references at pfn = mfn */ +#define XENFEAT_grant_map_identity 12 + #define XENFEAT_NR_SUBMAPS 1 #endif /* __XEN_PUBLIC_FEATURES_H__ */ -- 2.20.1