Re: [PATCH v10 44/59] hw/xen: Support mapping grant frames

[David Woodhouse]

On 13 February 2023 16:31:57 CET, Paul Durrant <xadimgnik@gmail.com> wrote:
>On 01/02/2023 14:31, David Woodhouse wrote:
>> From: David Woodhouse <dwmw@amazon.co.uk>
>> 
>> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
>> ---
>>   hw/i386/kvm/xen_gnttab.c  | 74 ++++++++++++++++++++++++++++++++++++++-
>>   hw/i386/kvm/xen_overlay.c |  2 +-
>>   hw/i386/kvm/xen_overlay.h |  2 ++
>>   3 files changed, 76 insertions(+), 2 deletions(-)
>> 
>> diff --git a/hw/i386/kvm/xen_gnttab.c b/hw/i386/kvm/xen_gnttab.c
>> index ef8857e50c..cd8c3ae60d 100644
>> --- a/hw/i386/kvm/xen_gnttab.c
>> +++ b/hw/i386/kvm/xen_gnttab.c
>> @@ -37,13 +37,27 @@ OBJECT_DECLARE_SIMPLE_TYPE(XenGnttabState, XEN_GNTTAB)
>>   #define XEN_PAGE_SHIFT 12
>>   #define XEN_PAGE_SIZE (1ULL << XEN_PAGE_SHIFT)
>>   +#define ENTRIES_PER_FRAME_V1 (XEN_PAGE_SIZE / sizeof(grant_entry_v1_t))
>> +#define ENTRIES_PER_FRAME_V2 (XEN_PAGE_SIZE / sizeof(grant_entry_v2_t))
>> +
>>   struct XenGnttabState {
>>       /*< private >*/
>>       SysBusDevice busdev;
>>       /*< public >*/
>>   +    QemuMutex gnt_lock;
>> +
>>       uint32_t nr_frames;
>>       uint32_t max_frames;
>> +
>> +    union {
>> +        grant_entry_v1_t *v1;
>> +        grant_entry_v2_t *v2;
>> +    } entries;
>> +
>
>If you want to have v2 support, don't you need status frames too?

If/when we add v2 support we will need that, but not yet. Seemed harmless 
enough to have the union with the right types from day one though.