linux-kernel - Re: [PATCH 12/15] KVM: MTRR: introduce mtrr_for_each_mem

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Date:	Mon, 01 Jun 2015 11:33:08 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
CC:	gleb@...nel.org, mtosatti@...hat.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 12/15] KVM: MTRR: introduce mtrr_for_each_mem_type



On 30/05/2015 12:59, Xiao Guangrong wrote:
> +struct mtrr_looker {
> +	/* input fields. */
> +	struct kvm_mtrr *mtrr_state;
> +	u64 start;
> +	u64 end;

s/looker/iter/ or s/looker/lookup/

> +static void mtrr_lookup_start(struct mtrr_looker *looker)
> +{
> +	looker->mem_type = -1;
> +
> +	if (!looker->mtrr_state->mtrr_enabled) {
> +		looker->partial_map = true;
> +		return;
> +	}
> +
> +	if (!mtrr_lookup_fixed_start(looker))
> +		mtrr_lookup_var_start(looker);
> +}
> +

Separating mtrr_lookup_start and mtrr_lookup_init is weird.

There are common parts of mtrr_lookup_*_start and mtrr_lookup_*_next.  
For example this:

> +	looker->mem_type = looker->mtrr_state->fixed_ranges[index];
> +	looker->start = fixed_mtrr_range_end_addr(seg, index);
> +	return true;

in mtrr_lookup_fixed_start is the same as this:

> 
> +	end = fixed_mtrr_range_end_addr(looker->seg, looker->index);
> +
> +	/* switch to next segment. */
> +	if (end >= eseg->end) {
> +		looker->seg++;
> +		looker->index = 0;
> +
> +		/* have looked up for all fixed MTRRs. */
> +		if (looker->seg >= ARRAY_SIZE(fixed_seg_table))
> +			return mtrr_lookup_var_start(looker);
> +
> +		end = fixed_mtrr_range_end_addr(looker->seg, looker->index);
> +	}
> +
> +	looker->mem_type = mtrr_state->fixed_ranges[looker->index];
> +	looker->start = end;

in mtrr_lookup_fixed_next.  Can you try to make them more common?

Basically you should have

+#define mtrr_for_each_mem_type(_looker_, _mtrr_, _gpa_start_, _gpa_end_) \
+	for (mtrr_lookup_init(_looker_, _mtrr_, _gpa_start_, _gpa_end_); \
+	     !mtrr_lookup_end(_looker_); mtrr_lookup_next(_looker_))

Paolo
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