Re: [PATCH v2 5/5] sgx: Reset the vEPC regions during VM reboot

[Paolo Bonzini]

On 22/10/21 21:27, Yang Zhong wrote:
> +
> +    for (j = 0; j < num; j++) {
> +        epc = pcms->sgx_epc.sections[j];
> +        hostmem = MEMORY_BACKEND(epc->hostmem);
> +        fd = memory_region_get_fd(host_memory_backend_get_memory(hostmem));
> +
> +        failures = ioctl(fd, SGX_IOC_VEPC_REMOVE_ALL);
> +        if (failures < 0) {
> +            return failures;
> +        } else if (failures > 0) {
> +            /* Remove SECS pages */
> +            sleep(1);
> +            failures_1 = ioctl(fd, SGX_IOC_VEPC_REMOVE_ALL);
> +        }
> +
> +        /*
> +         * The host or guest can support 8 EPC sections, use the
> +         * corresponding bit to show each section removal status.
> +         */
> +        if (failures_1) {
> +            set_bit(j, &ret);
> +        }
> +    }

This sleep is not necessary, just do two tries on all the regions.  So 
something like

    int failures;

    /*
     * The second pass is needed to remove SECS pages that could not
     * be removed during the first.
     */
    for (i = 0; i < 2; i++) {
        failures = 0;
        for (j = 0; j < pcms->sgx_epc.nr_sections; j++) {
            epc = pcms->sgx_epc.sections[j];
            hostmem = MEMORY_BACKEND(epc->hostmem);
            fd = 
memory_region_get_fd(host_memory_backend_get_memory(hostmem));

            r = ioctl(fd, SGX_IOC_VEPC_REMOVE_ALL);
            if (r < 0) {
                return r;
            }
            if (r > 0) {
                /* SECS pages remain */
                failures++;
                if (pass == 1) {
                    error_report("cannot reset vEPC section %d\n", j);
                }
            }
        }
        if (!failures) {
            return 0;
        }
    }
    return failures;

is enough, without any need to do further retries.

Paolo