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

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Date:	Tue, 09 Jun 2015 10:45:50 +0800
From:	Xiao Guangrong <guangrong.xiao@...ux.intel.com>
To:	David Matlack <dmatlack@...gle.com>
CC:	Paolo Bonzini <pbonzini@...hat.com>,
	Gleb Natapov <gleb@...nel.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	kvm list <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 12/15] KVM: MTRR: introduce mtrr_for_each_mem_type



On 06/09/2015 08:36 AM, David Matlack wrote:
> On Sat, May 30, 2015 at 3:59 AM, Xiao Guangrong
> <guangrong.xiao@...ux.intel.com> wrote:
>> It walks all MTRRs and gets all the memory cache type setting for the
>> specified range also it checks if the range is fully covered by MTRRs
>>
>> Signed-off-by: Xiao Guangrong <guangrong.xiao@...ux.intel.com>
>> ---
>>   arch/x86/kvm/mtrr.c | 183 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 183 insertions(+)
>>
>> diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
>> index e59d138..35f86303 100644
>> --- a/arch/x86/kvm/mtrr.c
>> +++ b/arch/x86/kvm/mtrr.c
>> @@ -395,6 +395,189 @@ void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu)
>>          INIT_LIST_HEAD(&vcpu->arch.mtrr_state.head);
>>   }
>>
>> +struct mtrr_looker {
>> +       /* input fields. */
>> +       struct kvm_mtrr *mtrr_state;
>> +       u64 start;
>> +       u64 end;
>> +
>> +       /* output fields. */
>> +       int mem_type;
>> +       /* [start, end) is fully covered in MTRRs? */
>
> s/fully/not fully/ ?

Yup, thanks for pointing it out.

>
>> +       bool partial_map;
>> +
>> +       /* private fields. */
>> +       union {
>> +               /* used for fixed MTRRs. */
>> +               struct {
>> +                       int index;
>> +                       int seg;
>> +               };
>> +
>> +               /* used for var MTRRs. */
>> +               struct {
>> +                       struct kvm_mtrr_range *range;
>> +                       /* max address has been covered in var MTRRs. */
>> +                       u64 start_max;
>> +               };
>> +       };
>> +
>> +       bool fixed;
>> +};
>> +
>> +static void mtrr_lookup_init(struct mtrr_looker *looker,
>> +                            struct kvm_mtrr *mtrr_state, u64 start, u64 end)
>> +{
>> +       looker->mtrr_state = mtrr_state;
>> +       looker->start = start;
>> +       looker->end = end;
>> +}
>> +
>> +static u64 fixed_mtrr_range_end_addr(int seg, int index)
>> +{
>> +       struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
>> +
>> +        return mtrr_seg->start + mtrr_seg->range_size * index;
>
> Should be (index + 1)?

Good eyes, will fix.

>
>> +}
>> +
>> +static bool mtrr_lookup_fixed_start(struct mtrr_looker *looker)
>> +{
>> +       int seg, index;
>> +
>> +       if (!looker->mtrr_state->fixed_mtrr_enabled)
>> +               return false;
>> +
>> +       seg = fixed_mtrr_addr_to_seg(looker->start);
>> +       if (seg < 0)
>> +               return false;
>> +
>> +       looker->fixed = true;
>> +       index = fixed_mtrr_addr_seg_to_range_index(looker->start, seg);
>> +       looker->index = index;
>> +       looker->seg = seg;
>> +       looker->mem_type = looker->mtrr_state->fixed_ranges[index];
>> +       looker->start = fixed_mtrr_range_end_addr(seg, index);
>> +       return true;
>> +}
>> +
>> +static bool match_var_range(struct mtrr_looker *looker,
>> +                           struct kvm_mtrr_range *range)
>> +{
>> +       u64 start, end;
>> +
>> +       var_mtrr_range(range, &start, &end);
>> +       if (!(start >= looker->end || end <= looker->start)) {
>> +               looker->range = range;
>> +               looker->mem_type = range->base & 0xff;
>> +
>> +               /*
>> +                * the function is called when we do kvm_mtrr.head walking
>> +                * that means range has the minimum base address interleaves
>> +                * with [looker->start_max, looker->end).
>> +                */
>
> I'm having trouble understanding this comment. I think this is what you
> are trying to say:
>
>    this function is called when we do kvm_mtrr.head walking. range has the
>    minimum base address which interleaves [looker->start_max, looker->end).
>
> Let me know if I parsed it wrong.

Yes, it is, will improve the comment.

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