From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57697) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bjscm-0003E2-EW for qemu-devel@nongnu.org; Tue, 13 Sep 2016 14:40:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bjsci-00054u-H2 for qemu-devel@nongnu.org; Tue, 13 Sep 2016 14:40:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:36038) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bjsci-00054l-Ax for qemu-devel@nongnu.org; Tue, 13 Sep 2016 14:40:00 -0400 Date: Tue, 13 Sep 2016 21:39:57 +0300 From: "Michael S. Tsirkin" Message-ID: <20160913213912-mutt-send-email-mst@kernel.org> References: <147377800565.11859.4411044563640180545.stgit@brijesh-build-machine> <147377820679.11859.11888810000954712438.stgit@brijesh-build-machine> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <147377820679.11859.11888810000954712438.stgit@brijesh-build-machine> Subject: Re: [Qemu-devel] [RFC PATCH v1 20/22] fw_cfg: sev: disable dma in real mode List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Brijesh Singh Cc: ehabkost@redhat.com, crosthwaite.peter@gmail.com, armbru@redhat.com, p.fedin@samsung.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, pbonzini@redhat.com, rth@twiddle.net On Tue, Sep 13, 2016 at 10:50:06AM -0400, Brijesh Singh wrote: > In SEV-enabled guest dma should be performed on shared pages. Since > the SeaBIOS executes in non PAE mode and does not have access to C-bit > to create a shared page hence disable the dma operation when reading > from fw_cfg interface. > > Signed-off-by: Brijesh Singh Why do we need new interfaces for this though? Just set dma_enabled=false on command line. > --- > hw/nvram/fw_cfg.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c > index 6a68e59..aca99e9 100644 > --- a/hw/nvram/fw_cfg.c > +++ b/hw/nvram/fw_cfg.c > @@ -24,6 +24,7 @@ > #include "qemu/osdep.h" > #include "hw/hw.h" > #include "sysemu/sysemu.h" > +#include "sysemu/kvm.h" > #include "sysemu/dma.h" > #include "hw/boards.h" > #include "hw/isa/isa.h" > @@ -1009,6 +1010,11 @@ static void fw_cfg_io_realize(DeviceState *dev, Error **errp) > FWCfgIoState *s = FW_CFG_IO(dev); > SysBusDevice *sbd = SYS_BUS_DEVICE(dev); > > + /* disable dma on fw_cfg when SEV is enabled */ > + if (kvm_sev_enabled()) { > + qdev_prop_set_bit(dev, "dma_enabled", false); > + } > + > /* when using port i/o, the 8-bit data register ALWAYS overlaps > * with half of the 16-bit control register. Hence, the total size > * of the i/o region used is FW_CFG_CTL_SIZE */