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 <brijesh.si...@amd.com>
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=]<name>,file=<file>
add named fw_cfg entry from file
-fw_cfg [name=]<name>,string=<str>
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 */
