Re: [PULL 027/115] hw/i386/vmport: Propagate IOPort read to vCPU EAX register

[Liran Alon]

On 23/06/2020 11:46, Laurent Vivier wrote:
> On 11/06/2020 21:43, Paolo Bonzini wrote:
> > From: Liran Alon <liran.alon@oracle.com>
> >
> > vmport_ioport_read() returns the value that should propagate to vCPU EAX
> > register when guest reads VMPort IOPort (i.e. By x86 IN instruction).
> >
> > However, because vmport_ioport_read() calls cpu_synchronize_state(), the
> > returned value gets overridden by the value in QEMU vCPU EAX register.
> > i.e. cpu->env.regs[R_EAX].
> >
> > To fix this issue, change vmport_ioport_read() to explicitly override
> > cpu->env.regs[R_EAX] with the value it wish to propagate to vCPU EAX
> > register.
> >
> > Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
> > Signed-off-by: Liran Alon <liran.alon@oracle.com>
> > Message-Id: <20200312165431.82118-4-liran.alon@oracle.com>
> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> > ---
> >   hw/core/machine.c |  1 +
> >   hw/i386/vmport.c  | 32 +++++++++++++++++++++++++++++---
> >   2 files changed, 30 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/core/machine.c b/hw/core/machine.c
> > index bb3a7b18b1..83f0fe5c91 100644
> > --- a/hw/core/machine.c
> > +++ b/hw/core/machine.c
> > @@ -43,6 +43,7 @@ GlobalProperty hw_compat_4_2[] = {
> >       { "qxl", "revision", "4" },
> >       { "qxl-vga", "revision", "4" },
> >       { "fw_cfg", "acpi-mr-restore", "false" },
> > +    { "vmport", "x-read-set-eax", "off" },
> This is modifying the hw_compat_4_2 properties while qemu-5.0 has been
> already released. I think all the vmport property updates [1] should go
> to hw_compat_5_0.
>
> Liran? Paolo?

When I submitted these patches, QEMU 5.0 wasn't released yet. That's why 
I updated hw_compat_4_2[].

Having said that, I believe the compatibility risk here is very small 
and therefore because QEMU 5.0 was
released for a very short time-span before these patches were merged, 
I'm not sure it's really preferable
to move these flags to hw_compat_5_0[]. But I will leave this for Paolo 
to decide.
(Note that moving these flags will also risk in comparability people 
running with current patches and
specifying explicitly machine-type 5.0...)

-Liran

> Thanks,
> Laurent
>
> [1]
>
> b889212973da hw/i386/vmport: Propagate IOPort read to vCPU EAX register
> 0342ee761ef2 hw/i386/vmport: Set EAX to -1 on failed and unsupported
> commands
> f8bdc550370f hw/i386/vmport: Report vmware-vmx-type in CMD_GETVERSION
> aaacf1c15a22 hw/i386/vmport: Add support for CMD_GETBIOSUUID
>
>      { "vmport", "x-read-set-eax", "off" },
>      { "vmport", "x-signal-unsupported-cmd", "off" },
>      { "vmport", "x-report-vmx-type", "off" },
>      { "vmport", "x-cmds-v2", "off" },