Hi Joelle,
On 01.08.23 03:46, Joelle van Dyne wrote:
On Tue, Jul 18, 2023 at 7:16 AM Stefan Berger <stef...@linux.ibm.com> wrote:
On 7/17/23 09:46, Igor Mammedov wrote:
On Fri, 14 Jul 2023 00:09:21 -0700
Joelle van Dyne <j...@getutm.app> wrote:
Since this device is gated to only build for targets with the PC
configuration, we should use the ISA bus like with TPM TIS.
does it affect migration in any way?
From guest pov it looks like there a new ISA device will appear
and then if you do ping pong migration between old - new QEMU will really it
work?
If it will, then commit message here shall describe why it safe and why it works
I would just leave the existing device as-is. This seems safest and we know
thta it works.
Stefan
Alexander, do you have any comments here? I know you wanted to move
away from the default bus. The concern is that switching from the
default bus to the ISA bus may cause issues in migration. The current
course of action is to drop this patch.
The big problem I have with the CRB device is this code:
https://gitlab.com/qemu-project/qemu/-/blob/master/hw/tpm/tpm_crb.c?ref_type=heads#L297-305
It's a device that maps itself autonomously into system memory. The way
mapping is supposed to work is that the parent of the device maps it
into a bus region. If the parent is a machine, it is free to also map it
into system memory. But a device should not even know what system memory
is :).
That said, I'm happy if we just introduce a new "sane" sysdev TPM CRB
device that we use for non-PCs and leave the current layering violating
one as is.
Alex
