[PATCH v3 14/19] KVM: arm64: ITS: Add infrastructure for table lookup

[Auger Eric]

Hi,

On 21/03/2017 19:12, Andre Przywara wrote:
> Hi,
> 
> On 06/03/17 11:34, Eric Auger wrote:
>> Add a generic lookup_table() helper whose role consists in
>> scanning a contiguous table located in guest RAM and applying
>> a callback on each entry. Entries can be handled as linked lists
>> since the callback may return an offset to the next entry and
>> also tell that an entry is the last one.
>>
>> Helper functions also are added to compute the device/event ID
>> offset to the next DTE/ITE.
>>
>> Signed-off-by: Eric Auger <eric.auger at redhat.com>
>> ---
>>  virt/kvm/arm/vgic/vgic-its.c | 119 +++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 119 insertions(+)
>>
>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
>> index 1cd6ae6..cf04776 100644
>> --- a/virt/kvm/arm/vgic/vgic-its.c
>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>> @@ -181,6 +181,8 @@ static struct its_ite *find_ite(struct vgic_its *its, u32 device_id,
>>  #define VITS_ESZ 8
>>  #define VITS_TYPER_IDBITS 0xF
>>  #define VITS_TYPER_DEVBITS 0xF
>> +#define VITS_DTE_MAX_DEVID_OFFSET GENMASK(19, 0)
>> +#define VITS_ITE_MAX_EVENTID_OFFSET GENMASK(16, 0)
> 
> GENMASK here is a bit misleading, I think (BIT(20) - 1) would be
> clearer, wouldn't it?

done
> 
>>  
>>  /*
>>   * Finds and returns a collection in the ITS collection table.
>> @@ -1607,6 +1609,123 @@ int vgic_its_attr_regs_access(struct kvm_device *dev,
>>  	return 0;
>>  }
>>  
>> +static u32 compute_next_devid_offset(struct list_head *h,
>> +				     struct its_device *dev)
>> +{
>> +	struct list_head *e = &dev->dev_list;
>> +	struct its_device *next;
>> +	u32 next_offset;
>> +
>> +	if (e->next == h)
>> +		return 0;
>> +	next = list_entry(e->next, struct its_device, dev_list);
>> +	next_offset = next->device_id - dev->device_id;
>> +
>> +	return next_offset < VITS_DTE_MAX_DEVID_OFFSET ?
>> +			next_offset : VITS_DTE_MAX_DEVID_OFFSET;
> 
> 	return min(next_offset, VITS_DTE_MAX_DEVID_OFFSET);
> 
>> +}
>> +
>> +static u32 compute_next_eventid_offset(struct list_head *h,
>> +				       struct its_ite *ite)
>> +{
>> +	struct list_head *e = &ite->ite_list;
>> +	struct its_ite *next;
>> +	u32 next_offset;
>> +
>> +	if (e->next == h)
>> +		return 0;
>> +	next = list_entry(e->next, struct its_ite, ite_list);
>> +	next_offset = next->event_id - ite->event_id;
>> +
>> +	return next_offset < VITS_ITE_MAX_EVENTID_OFFSET ?
>> +			next_offset : VITS_ITE_MAX_EVENTID_OFFSET;
> 
> 	return min(next_offset, VITS_ITE_MAX_EVENTID_OFFSET);
> 
>> +}
>> +
>> +static int next_segment(unsigned long len, int offset)
> 
> Isn't "segment" a page, really? And thus should be named like this?

I lazily reused kvm_main.c homonymous function, hence the name. I may
expose the function kvm_host.h
> 
>> +{
>> +	if (len > PAGE_SIZE - offset)
>> +		return PAGE_SIZE - offset;
>> +	else
>> +		return len;
>> +}
> 
> Can be: return min(len, PAGE_SIZE - offset); which means it could be a
> macro even.
> 
>> +
>> +/**
>> + * entry_fn_t - Callback called on a table entry restore path
>> + * @its: its handle
>> + * @id: id of the entry
>> + * @addr: kernel VA of the entry
>> + * @opaque: pointer to an opaque data
>> + * @next_offset: minimal ID offset to the next entry. 0 if this
>> + * entry is the last one, 1 if the entry is invalid, >= 1 if an
>> + * entry's next_offset field was truly decoded
>> + *
>> + * Return: < 0 on error, 0 otherwise
>> + */
>> +typedef int (*entry_fn_t)(struct vgic_its *its, u32 id, void *addr,
>> +			  void *opaque, u32 *next_offset);
>> +
>> +/**
>> + * lookup_table - scans a contiguous table in guest RAM and applies a function
>> + * to each entry
>> + *
>> + * @its: its handle
>> + * @base: base gpa of the table
>> + * @size: size of the table in bytes
>> + * @esz: entry size in bytes
>> + * @start_id: first entry's ID
>> + * @fn: function to apply on each entry
>> + *
>> + * Return: < 0 on error, 1 if last element identified, 0 otherwise
>> + */
>> +static int lookup_table(struct vgic_its *its, gpa_t base, int size, int esz,
> 
>    ^^^^^^
> Won't this trigger a build warning when building at this patch only?
yes I corrected that

Thanks

Eric
> 
> The rest looks fine.
> 
> Cheers,
> Andre
> 
> 
>> +			int start_id, entry_fn_t fn, void *opaque)
>> +{
>> +	gpa_t gpa = base, top = base + size - 1;
>> +	unsigned long len = top - gpa;
>> +	int ret, seg, offset = offset_in_page(gpa);
>> +	gfn_t gfn = gpa >> PAGE_SHIFT;
>> +	u32 id = start_id + (gpa - base)/esz;
>> +	struct kvm *kvm = its->dev->kvm;
>> +	kvm_pfn_t pfn;
>> +
>> +	while ((seg = next_segment(len, offset)) != 0) {
>> +		u32 next_offset;
>> +		bool writeable;
>> +		void *addr;
>> +
>> +		pfn = gfn_to_pfn_prot(kvm, gfn, true, &writeable);
>> +		if (is_error_noslot_pfn(pfn))
>> +			return -EINVAL;
>> +		addr = phys_to_virt((u64)pfn << PAGE_SHIFT);
>> +		addr += offset;
>> +
>> +		while (seg > 0) {
>> +			size_t byte_offset;
>> +
>> +			ret = fn(its, id, addr, opaque, &next_offset);
>> +			if (ret < 0 || (!ret && !next_offset))
>> +				goto out;
>> +
>> +			byte_offset = next_offset * esz;
>> +
>> +			id += next_offset;
>> +			gpa += byte_offset;
>> +			addr += byte_offset;
>> +			seg -= byte_offset;
>> +		}
>> +		kvm_release_pfn_clean(pfn);
>> +
>> +		len = top - gpa;
>> +		offset = offset_in_page(gpa);
>> +		gfn = gpa >> PAGE_SHIFT;
>> +		id = start_id + (gpa - base)/esz;
>> +	}
>> +	return 0;
>> +out:
>> +	kvm_release_pfn_clean(pfn);
>> +	return (ret < 0 ? ret : 1);
>> +}
>> +
>>  /**
>>   * vgic_its_flush_pending_tables - Flush the pending tables into guest RAM
>>   */
>>
> 
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