Re: [Xen-devel] [PATCH v8 1/5] x86: allow reading MSR_IA32_TSC with XENPF_resource_op

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.01.15 at 09:04, <chao.p.peng@xxxxxxxxxxxxxxx> wrote:
> +            else
> +            {
> +                unsigned long irqflags;

Some gcc versions can't figure out that this variable doesn't get used
uninitialized, and hence warn about it. I fixed this while committing, at
once changing the name to the more conventional "flags". Please be
more careful with such conditional uses in the future.

Jan

> +                /*
> +                 * If next entry is MSR_IA32_TSC read, then the actual 
> rdtscll
> +                 * is performed together with current entry, with IRQ 
> disabled.
> +                 */
> +                bool_t read_tsc = (i < ra->nr_done - 1 &&
> +                                   unlikely(entry[1].idx == MSR_IA32_TSC));
> +
> +                if ( unlikely(read_tsc) )
> +                    local_irq_save(irqflags);
> +
> +                ret = rdmsr_safe(entry->idx, entry->val);
> +
> +                if ( unlikely(read_tsc) )
> +                {
> +                    rdtscll(tsc);
> +                    local_irq_restore(irqflags);
> +                }
> +            }
>              break;



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