Re: [PATCH v5 12/22] KVM: arm64: vgic-its: Interpret MAPD ITT_addr field

Auger Eric
2017-04-27T19:19:05Z

Hi,

On 27/04/2017 20:09, Christoffer Dall wrote:
> On Thu, Apr 27, 2017 at 07:44:25PM +0200, Auger Eric wrote:
>> Hi,
>>
>> On 27/04/2017 18:43, Christoffer Dall wrote:
>>> On Fri, Apr 14, 2017 at 12:15:24PM +0200, Eric Auger wrote:
>>>> Up to now the MAPD ITT_addr had been ignored. We will need it
>>>> for save/restore. Let's record it in the its_device struct.
>>>>
>>>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>>>>
>>>> ---
>>>> v4 -> v5:
>>>> - its_cmd_get_ittaddr macro now returns the actual ITT GPA
>>>>
>>>> v3 -> v4:
>>>> - in vgic_its_cmd_handle_mapd, itt_addr directly is shifted
>>>> - correct ittaddr bitmask to support 48bit GPA
>>>> ---
>>>> virt/kvm/arm/vgic/vgic-its.c | 4 ++++
>>>> 1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
>>>> index 0f3c8f3..757598d 100644
>>>> --- a/virt/kvm/arm/vgic/vgic-its.c
>>>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>>>> @@ -106,6 +106,7 @@ struct its_device {
>>>> /* the head for the list of ITTEs */
>>>> struct list_head itt_head;
>>>> u32 nb_eventid_bits;
>>>> + gpa_t itt_addr;
>>>> u32 device_id;
>>>> };
>>>>
>>>> @@ -569,6 +570,7 @@ static u64 its_cmd_mask_field(u64 *its_cmd, int word, int shift, int size)
>>>> #define its_cmd_get_id(cmd) its_cmd_mask_field(cmd, 1, 0, 32)
>>>> #define its_cmd_get_physical_id(cmd) its_cmd_mask_field(cmd, 1, 32, 32)
>>>> #define its_cmd_get_collection(cmd) its_cmd_mask_field(cmd, 2, 0, 16)
>>>> +#define its_cmd_get_ittaddr(cmd) (its_cmd_mask_field(cmd, 2, 8, 47) << 8)
>>>
>>> Why 47? The ITT_addr field is bits [51:8] unless I'm looking at
>>> something wrong?
>>
>> Initially I limited to 48 bits since I found in the code:
>>
>> /*
>> * We only implement 48 bits of PA at the moment, although the ITS
>> * supports more. Let's be restrictive here.
>> */
>> #define BASER_ADDRESS(x) ((x) & GENMASK_ULL(47, 16))
>> #define CBASER_ADDRESS(x) ((x) & GENMASK_ULL(47, 12))
>>
>> But practically as I encode the ITT addr field on 52 bits now in the DTE
>> there is no reason anymore.
>
> Well, regardless, shouldn't you be bassing 44 to its_cmd_mask_field(),
> because you're shifting left 8 bits afterwards?

Hum yes that's correct. Andre already warned me against that mistake :-(

Thanks

Eric
>
> Thanks,
> -Christoffer
>
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