Re: [RFC PATCH v3 16/36] i386/tdx: Set kvm_readonly_mem_enabled to false for TDX VM

[Xiaoyao Li]

On 3/19/2022 1:11 AM, Isaku Yamahata wrote:
> On Thu, Mar 17, 2022 at 09:58:53PM +0800,
> Xiaoyao Li <xiaoyao.li@intel.com> wrote:
>
> > TDX only supports readonly for shared memory but not for private memory.
> >
> > In the view of QEMU, it has no idea whether a memslot is used by shared
> > memory of private. Thus just mark kvm_readonly_mem_enabled to false to
> > TDX VM for simplicity.
> >
> > Note, pflash has dependency on readonly capability from KVM while TDX
> > wants to reuse pflash interface to load TDVF (as OVMF). Excuse TDX VM
> > for readonly check in pflash.
> >
> > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > ---
> >   hw/i386/pc_sysfw.c    | 2 +-
> >   target/i386/kvm/tdx.c | 9 +++++++++
> >   2 files changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
> > index c8b17af95353..75b34d02cb4f 100644
> > --- a/hw/i386/pc_sysfw.c
> > +++ b/hw/i386/pc_sysfw.c
> > @@ -245,7 +245,7 @@ void pc_system_firmware_init(PCMachineState *pcms,
> >           /* Machine property pflash0 not set, use ROM mode */
> >           x86_bios_rom_init(MACHINE(pcms), "bios.bin", rom_memory, false);
> >       } else {
> > -        if (kvm_enabled() && !kvm_readonly_mem_enabled()) {
> > +        if (kvm_enabled() && (!kvm_readonly_mem_enabled() && !is_tdx_vm())) {
>
> Is this called before tdx_kvm_init()?

yes.

pc_init1()/ pc_q35_init()
 pc_memory_init()
    pc_system_firmware_init()

is called after configure_accelerator() to configure kvm.