Re: [RFC PATCH 06/15] virt: tdx-guest: Support TDI bind and unbind operations

[Nikolay Borisov]

On 24.09.26 г. 7:10 ч., Zhenzhong Duan wrote:
> Introduce support for binding and unbinding the Trust Device Interface
> (TDI) using the TDCM_OP_BIND and TDCM_OP_UNBIND commands.
>
> Executing TDCM_OP_BIND transitions the TDI state to a locked state
> (TDI_STATE_CONFIG_LOCKED). Add a sanity check following the bind operation
> to verify this state transition succeeded before finalizing device locking.
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxx>
> ---
>   drivers/virt/coco/tdx-guest/connect.c | 75 +++++++++++++++++++++++++++
>   1 file changed, 75 insertions(+)
>
> diff --git a/drivers/virt/coco/tdx-guest/connect.c b/drivers/virt/coco/tdx-guest/connect.c
> index 1f52a187b30f..e36515fc43ef 100644
> --- a/drivers/virt/coco/tdx-guest/connect.c
> +++ b/drivers/virt/coco/tdx-guest/connect.c
> @@ -159,8 +159,67 @@ static bool tdx_is_dev_teeio_support(struct tdx_devsec *tdevsec)
>   	return !!rsp->is_supported;
>   }
>   

<snip>

> +
>   static struct pci_tsm *tdx_devsec_lock(struct tsm_dev *tsm_dev, struct pci_dev *pdev)
>   {
> +	u8 state;
>   	int ret;
>   
>   	struct tdx_devsec *tdevsec __free(kfree) = kzalloc(sizeof(*tdevsec), GFP_KERNEL);
> @@ -174,6 +233,19 @@ static struct pci_tsm *tdx_devsec_lock(struct tsm_dev *tsm_dev, struct pci_dev *
>   	if (!tdx_is_dev_teeio_support(tdevsec))
>   		return ERR_PTR(-EOPNOTSUPP);
>   
> +	struct tdx_devsec *tdevsec_bind __free(tdx_tdi_unbind_dev) = tdx_tdi_bind_dev(tdevsec);
> +	if (IS_ERR(tdevsec_bind))
> +		return ERR_CAST(tdevsec_bind);
> +
> +	ret = tdx_tdi_read_state(tdevsec, &state);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	if (state != TDI_STATE_CONFIG_LOCKED)
> +		return ERR_PTR(-EIO);
> +
> +	retain_and_null_ptr(tdevsec_bind);
> +
>   	return &no_free_ptr(tdevsec)->pci.base_tsm;
>   }
>   
> @@ -181,6 +253,9 @@ static void tdx_devsec_unlock(struct pci_tsm *tsm)
>   {
>   	struct tdx_devsec *tdevsec = to_tdx_devsec(tsm);
>   
> +	if (WARN_ON(tdx_tdi_unbind_dev(tdevsec)))
> +		return;

<Thinking out loud>

So unlock involves calling TDCM_UNBIND which in turn might fail for any 
number of reasons and yet we have no way of communicating that. So after 
an unlock a TD might want to rebind and issue bind on a device which is 
already bound because prior unbind failed. Is this something we should 
be worried about ?

> +
>   	kfree(tdevsec);
>   }
>