On 2/12/24 02:44, Kirill A. Shutemov wrote:
> +static void tdx_kexec_stop_conversion(bool crash)
> +{
> + /* Stop new private<->shared conversions */
> + conversion_allowed = false;
> +
> + /*
> + * Make sure conversion_allowed is cleared before checking
> + * conversions_in_progress.
> + */
> + barrier();
> +
> + /*
> + * Crash kernel reaches here with interrupts disabled: can't wait for
> + * conversions to finish.
> + *
> + * If race happened, just report and proceed.
> + */
> + if (!crash) {
> + unsigned long timeout;
> +
> + /*
> + * Wait for in-flight conversions to complete.
> + *
> + * Do not wait more than 30 seconds.
> + */
> + timeout = 30 * USEC_PER_SEC;
> + while (atomic_read(&conversions_in_progress) && timeout--)
> + udelay(1);
> + }
> +
> + if (atomic_read(&conversions_in_progress))
> + pr_warn("Failed to finish shared<->private conversions\n");
> +}
I'd really prefer we find a way to do this with actual locks, especially
'conversion_allowed'.
This is _awfully_ close to being able to be handled by a rwsem where the
readers are the converters and tdx_kexec_stop_conversion() takes a write.
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