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Re: [PATCH v1] x86/mm: avoid inadvertently degrading a TLB flush to local only
- To: David Vrabel <dvrabel@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 20 Apr 2022 08:34:21 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, David Vrabel <dvrabel@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 20 Apr 2022 06:34:37 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 19.04.2022 17:03, David Vrabel wrote:
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -5071,11 +5071,10 @@ l1_pgentry_t *virt_to_xen_l1e(unsigned long v)
> #define lNf_to_l1f(f) (((f) & _PAGE_PRESENT) ? ((f) & ~_PAGE_PSE) : (f))
>
> /*
> - * map_pages_to_xen() can be called with interrupts disabled during
> - * early bootstrap. In this case it is safe to use flush_area_local()
> - * and avoid locking because only the local CPU is online.
> + * map_pages_to_xen() can be called early in boot before any other
> + * CPUs are online. Use flush_area_local() in this case.
> */
> -#define flush_area(v,f) (!local_irq_is_enabled() ? \
> +#define flush_area(v,f) (system_state < SYS_STATE_smp_boot ? \
> flush_area_local((const void *)v, f) : \
> flush_area_all((const void *)v, f))
>
I agree with the change, but I wonder whether it wouldn't better be
accompanied by an assertion proving that IRQs are enabled. But wait -
flush_area_mask() has such an assertion, so all is fine.
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Jan
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