Messages in this thread | | | Date | Mon, 26 Feb 2024 05:58:23 -0800 | Subject | Re: [PATCHv7 10/16] x86/tdx: Convert shared memory back to private on kexec | From | Dave Hansen <> |
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On 2/25/24 06:58, Kirill A. Shutemov wrote: > On Fri, Feb 23, 2024 at 11:39:07AM -0800, Dave Hansen wrote: .. >> 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. > > Any comments?
Looks a heck of a lot more straightforward to me.
> +static void tdx_kexec_stop_conversion(bool crash) > +{ > + /* Stop new private<->shared conversions */ > + if (!stop_memory_enc_conversion(!crash)) > + pr_warn("Failed to finish shared<->private conversions\n"); > +}
FWIW, this is one of those places that could use a temporary variable to help explain what is going on:
bool wait_for_lock = !crash;
/* * ... explain why it doesn't or shouldn't take the lock here */ if (!stop_memory_enc_conversion(wait_for_lock)) ...
This makes it understandable without looking at the called function.
> +bool stop_memory_enc_conversion(bool wait) > +{ > + if (!wait) > + return down_write_trylock(&mem_enc_lock); > + > + down_write(&mem_enc_lock); > + > + return true; > +}
This also needs a comment about why the lock isn't being released.
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