Re: [PATCH v5 1/4] firmware: scm: Add new SCM call API for switching memory ownership

[Dwivedi, Avaneesh Kumar (avani)]

On 6/2/2017 11:52 PM, Stephen Boyd wrote:
> On 06/02, Avaneesh Kumar Dwivedi wrote:
> > Two different processors on a SOC need to switch memory ownership
> > during load/unload. To enable this, level second memory map table
> second level page tables instead of level second memory map table
OK
> > need to be updated, which is done by secure layer.
> > This patch add the interface for making secure monitor call for
> s/add/adds/
OK.
> > memory ownership switching request.
> > diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
> > index bb16510..9da3c6d 100644
> > --- a/drivers/firmware/qcom_scm.c
> > +++ b/drivers/firmware/qcom_scm.c
> > @@ -292,6 +304,86 @@ int qcom_scm_pas_shutdown(u32 peripheral)
> >   }
> >   EXPORT_SYMBOL(qcom_scm_pas_shutdown);
> >   
> > +/**
> > + * qcom_scm_assign_mem() - Make a secure call to reassign memory ownership
> > + *
> > + * @mem_addr: mem region whose ownership need to be reassigned
> > + * @mem_sz:   size of the region.
> > + * @srcvm:    vmid for current set of owners, each set bit in
> > + *            flag indicate a unique owner
> > + * @newvm:    array having new owners and corrsponding permission
> > + *            flags
> > + * @dest_cnt: number of owners in next set.
> > + * Return next set of owners on success.
> > + */
> > +int qcom_scm_assign_mem(phys_addr_t mem_addr, size_t mem_sz, int srcvm,
> > +			struct qcom_scm_vmperm *newvm, int dest_cnt)
> > +{
> > +	unsigned long dma_attrs = DMA_ATTR_FORCE_CONTIGUOUS;
> > +	struct qcom_scm_current_perm_info *destvm;
> > +	struct qcom_scm_mem_map_info *mem;
> > +	phys_addr_t memory_phys;
> > +	phys_addr_t dest_phys;
> > +	phys_addr_t src_phys;
> > +	size_t mem_all_sz;
> > +	size_t memory_sz;
> > +	size_t dest_sz;
> > +	size_t src_sz;
> > +	int next_vm;
> > +	__le32 *src;
> > +	void *ptr;
> > +	int ret;
> > +	int i;
> Yay reverse christmas tre.
Shall be reversed?
> > +
> > +	src_sz = hweight_long(srcvm)*sizeof(*src);
> Please add space around that '*':
OK
> 	src_sz = hweight_long(srcvm) * sizeof(*src);
>
> > +	memory_sz = sizeof(*mem);
> > +	dest_sz = dest_cnt*sizeof(*destvm);
> > +	mem_all_sz = src_sz + memory_sz + dest_sz;
> > +
> > +	ptr = dma_alloc_attrs(__scm->dev, ALIGN(mem_all_sz, SZ_64),
> > +		&src_phys, GFP_KERNEL, dma_attrs);
> > +	if (!ptr) {
> > +		pr_err("mem alloc failed\n");
> We don't want memory allocation failure prints. Please remove.
OK
> > +		return -ENOMEM;
> > +	}
> Newline here!
OK
> > +	/* Fill source vmid detail */
> > +	src = (__le32 *)(ptr);
> Drop useless parenthesis around ptr please.
OK
> > +	ret = hweight_long(srcvm);
> len = hweight_long(...)?
OK, thought to use less local variables. will change
> > +	for (i = 0; i < ret; i++) {
> i to ret is really weird looking!
Will check if can use below suggestion
> > +		src[i] = cpu_to_le32(ffs(srcvm) - 1);
> > +		srcvm ^= 1 << (ffs(srcvm) - 1);
> > +	}
> What if the loop was written like:
>
> 	for_each_set_bit(i, &srcvm, sizeof(srcvm))
> 		src[i] = cpu_to_le32(i);
>
> I guess srvcm would have to be a long then.
Will check and adopt
> > +
> > +	/* Fill details of mem buff to map */
> > +	mem = (struct qcom_scm_mem_map_info *)(ptr + ALIGN(src_sz, SZ_64));
> Useless cast from void *.
OK
> > +	memory_phys = src_phys + ALIGN(src_sz, SZ_64);
> > +	mem[0].mem_addr = cpu_to_le64(mem_addr);
> > +	mem[0].mem_size = cpu_to_le64(mem_sz);
> > +
> > +	next_vm = 0;
> > +	/* Fill details of next vmid detail */
> > +	destvm = (struct qcom_scm_current_perm_info *)
> > +			(ptr + ALIGN(memory_sz, SZ_64) + ALIGN(src_sz, SZ_64));
> Useless cast from void.
OK
> > +	dest_phys = memory_phys + ALIGN(memory_sz, SZ_64);
> > +	for (i = 0; i < dest_cnt; i++) {
> > +		destvm[i].vmid = cpu_to_le32(newvm[i].vmid);
> > +		destvm[i].perm = cpu_to_le32(newvm[i].perm);
> > +		destvm[i].ctx = 0;
> > +		destvm[i].ctx_size = 0;
> > +		next_vm |= BIT(newvm[i].vmid);
> > +	}
> Newline please!
OK
> > +	ret = __qcom_scm_assign_mem(__scm->dev, memory_phys,
> > +		memory_sz, src_phys, src_sz, dest_phys, dest_sz);
> > +	dma_free_attrs(__scm->dev, ALIGN(mem_all_sz, SZ_64),
> > +		ptr, src_phys, dma_attrs);
> > +	if (ret == 0)
> > +		return next_vm;
> > +	else if (ret > 0)
> > +		return -ret;
> When is ret > 0?
SCM returns positive value in r1 register , and if r1 reg is non zero 
then that should be returned.
Not sure what that indicate.
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(qcom_scm_assign_mem);
> > +
> >   static int qcom_scm_pas_reset_assert(struct reset_controller_dev *rcdev,
> >   				     unsigned long idx)
> >   {

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