On Thu, Mar 17, 2022 at 09:58:53PM +0800,
Xiaoyao Li <xiaoyao.li@xxxxxxxxx> 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@xxxxxxxxx>
> ---
> 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()?
Thanks,
> /*
> * Older KVM cannot execute from device memory. So, flash
> * memory cannot be used unless the readonly memory kvm
> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
> index 94a9c1ea7e9c..1bb8211e74e6 100644
> --- a/target/i386/kvm/tdx.c
> +++ b/target/i386/kvm/tdx.c
> @@ -115,6 +115,15 @@ int tdx_kvm_init(MachineState *ms, Error **errp)
> get_tdx_capabilities();
> }
>
> + /*
> + * Set kvm_readonly_mem_allowed to false, because TDX only supports readonly
> + * memory for shared memory but not for private memory. Besides, whether a
> + * memslot is private or shared is not determined by QEMU.
> + *
> + * Thus, just mark readonly memory not supported for simplicity.
> + */
> + kvm_readonly_mem_allowed = false;
> +
> tdx_guest = tdx;
>
> return 0;
> --
> 2.27.0
>
>
--
Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
