From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35467) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bjub4-00015n-OY for qemu-devel@nongnu.org; Tue, 13 Sep 2016 16:46:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bjub0-00074X-PB for qemu-devel@nongnu.org; Tue, 13 Sep 2016 16:46:26 -0400 Received: from mail-sn1nam01on0070.outbound.protection.outlook.com ([104.47.32.70]:53600 helo=NAM01-SN1-obe.outbound.protection.outlook.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bjub0-000749-DR for qemu-devel@nongnu.org; Tue, 13 Sep 2016 16:46:22 -0400 From: Brijesh Singh References: <147377800565.11859.4411044563640180545.stgit@brijesh-build-machine> <147377820679.11859.11888810000954712438.stgit@brijesh-build-machine> <20160913213912-mutt-send-email-mst@kernel.org> Message-ID: <0dfffab0-4774-e458-2485-fa8e32d7dcdb@amd.com> Date: Tue, 13 Sep 2016 15:46:15 -0500 MIME-Version: 1.0 In-Reply-To: <20160913213912-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit 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: "Michael S. Tsirkin" Cc: brijesh.singh@amd.com, 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 Hi Michael, On 09/13/2016 01:39 PM, Michael S. Tsirkin wrote: > 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. > Thanks, i was not aware of dma_enabled=false command line option. Could you please tell me how to set this command line option? I see this in 'qemu --help' -fw_cfg [name=],file= add named fw_cfg entry from file -fw_cfg [name=],string= add named fw_cfg entry from string >> --- >> 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 */