Re: WARNING: CPU: 1 PID: 83 at arch/x86/kernel/cpu/sgx/main.c:446 ksgxd+0x1b7/0x1d0

[Haitao Huang]

Hi Paul

On Tue, 23 Aug 2022 08:48:52 -0500, Paul Menzel <pmenzel@xxxxxxxxxxxxx>  
wrote:

> Dear Dave,
>
>
> Am 20.08.22 um 08:13 schrieb Paul Menzel:
>
> > Am 19.08.22 um 20:28 schrieb Dave Hansen:
> > > On 8/19/22 09:02, Paul Menzel wrote:
> > > > On the Dell XPS 13 9370, Linux 5.18.16 prints the warning below:
> > > >
> > > > ```
> > > > [    0.000000] Linux version 5.18.0-4-amd64  
> > > > (debian-kernel@xxxxxxxxxxxxxxxx) (gcc-11 (Debian 11.3.0-5) 11.3.0,  
> > > > GNU ld (GNU Binutils for Debian) 2.38.90.20220713) #1 SMP  
> > > > PREEMPT_DYNAMIC Debian 5.18.16-1 (2022-08-10)
> > > > [    0.000000] Command line: BOOT_IMAGE=/vmlinuz-5.18.0-4-amd64  
> > > > root=UUID=56f398e0-1e25-4fda-aa9f-611dece4b333 ro quiet
> > > > […]
> > > > [    0.000000] DMI: Dell Inc. XPS 13 9370/0RMYH9, BIOS 1.21.0  
> > > > 07/06/2022
> > > > […]
> > > > [    0.235418] sgx: EPC section 0x40200000-0x45f7ffff
> >
> > > Would you be able to send the entire dmesg, along with:
> >  The log message are attached to the first message, where I missed to  
> > carbon-copy linux-sgx@ [1].
> >
> > >     cat /proc/iomem # (as root)
> > > and
> > >     cpuid -1 --raw
> >  I am going to provide that next week. (Side note, Intel might have  
> > some Dell XPS 9370 test machines in some QA lab.)
>
> Please find both outputs at the end of the file.

Could you also check output of "sudo rdmsr -x 0x3a"?
Also was CONFIG_X86_SGX_KVM set?

If CONFIG_X86_SGX_KVM is not set and bit 17 (SGX_LC) of the MSR 3A not set,
then I think following sequence during sgx_init is possible:

sgx_page_cache_init -> sgx_setup_epc_section
                       ->put all physical EPC pages in sgx_dirty_page_list.
Kick off ksgxd.
Later, sgx_drv_init returns none-zero due to this check:
    if (!cpu_feature_enabled(X86_FEATURE_SGX_LC))
        return -ENODEV;
sgx_vepc_init also returns none-zero if CONFIG_X86_SGX_KVM was not set.

And sgx_init will call kthread_stop(ksgxd_tsk):
    ret = sgx_drv_init();

    if (sgx_vepc_init() && ret)
        goto err_provision;
...
err_provision:
    misc_deregister(&sgx_dev_provision);

err_kthread:
    kthread_stop(ksgxd_tsk);


That triggers __sgx_sanitize_pages return early due to these lines:
    /* dirty_page_list is thread-local, no need for a lock: */
    while (!list_empty(dirty_page_list)) {
        if (kthread_should_stop())
            return;

And that would trigger (depends on timing?) the warning in ksgxd due to  
non-empty sgx_dirty_page_list
at that moment.

Thanks
Haitao