Re: [Xen-devel] [PATCH 04/14] x86/p2m: Fix locking in p2m_altp2m_lazy_copy()

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 11/21/18 3:21 PM, Andrew Cooper wrote:
> The gfn references need to remain held until after the p2m_set_entry() has
> completed.  This is only a latent bug for now, because there is no per-gfn
> locking and we recursively hold the main p2m locks.
> 
> Rearrange the code to have a single exit path, and defer taking the ap2m lock
> until it is necessary to do so.  Leave some comments behind to help people
> attempting to follow the logic.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wei.liu2@xxxxxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> CC: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> ---
>  xen/arch/x86/mm/p2m.c | 27 ++++++++++++++++++++-------
>  1 file changed, 20 insertions(+), 7 deletions(-)
> 
> diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
> index b5a59d6..ae9cb20 100644
> --- a/xen/arch/x86/mm/p2m.c
> +++ b/xen/arch/x86/mm/p2m.c
> @@ -2184,24 +2184,29 @@ bool_t p2m_altp2m_lazy_copy(struct vcpu *v, paddr_t 
> gpa,
>      unsigned long mask;
>      mfn_t mfn;
>      int rv;
> +    bool ret;

Thanks for the patches! This one looks good, except I think you'll want
to also change the return type of p2m_altp2m_lazy_copy() from bool_t to
bool.

With that:
Reviewed-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>


Thanks,
Razvan

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