On Sun, Feb 25, 2024 at 04:58:46PM +0200, Kirill A. Shutemov wrote:
> On Fri, Feb 23, 2024 at 11:39:07AM -0800, Dave Hansen wrote:
> > 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.
>
> Okay, here's what I come up with. It needs more testing.
I don't see a problem during testing.
#include <linux/delay.h> has to be dropped, but otherwise the patch is
fine to me.
Any feedback?
--
Kiryl Shutsemau / Kirill A. Shutemov
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