Re: [PATCH v4 05/27] lmb: make LMB memory map persistent and global

[Tom Rini <trini@konsulko.com>]

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On Mon, Oct 28, 2024 at 10:20:38PM +0100, Janne Grunau wrote:
> On Mon, Aug 26, 2024 at 05:29:18PM +0530, Sughosh Ganu wrote:
> > The current LMB API's for allocating and reserving memory use a
> > per-caller based memory view. Memory allocated by a caller can then be
> > overwritten by another caller. Make these allocations and reservations
> > persistent using the alloced list data structure.
> > 
> > Two alloced lists are declared -- one for the available(free) memory,
> > and one for the used memory. Once full, the list can then be extended
> > at runtime.
> > 
> > Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
> > Signed-off-by: Simon Glass <sjg@chromium.org>
> > [sjg: Optimise the logic to add a region in lmb_add_region_flags()]
> > [sjg: Use a stack to store pointer of lmb struct when running lmb tests]
> > ---
> > Changes since V3:
> > * Fix checkpatch warnings of spaces between function name and
> >   open parantheses.
> > * s/uint64_t/u64 as suggested by checkpatch.
> > * Remove unneccessary parantheses in lmb.c as suggested by checkpatch.
> > * Fix alignment in test/cmd/bdinfo.c as suggested by checkpatch.
> 
> [...]
>  
> >  drivers/iommu/apple_dart.c           |   8 +-
> 
> [...]
> 
> > diff --git a/drivers/iommu/apple_dart.c b/drivers/iommu/apple_dart.c
> > index 9327dea1e3..611ac7cd6d 100644
> > --- a/drivers/iommu/apple_dart.c
> > +++ b/drivers/iommu/apple_dart.c
> > @@ -70,7 +70,6 @@
> >  
> >  struct apple_dart_priv {
> >  	void *base;
> > -	struct lmb lmb;
> >  	u64 *l1, *l2;
> >  	int bypass, shift;
> >  
> > @@ -124,7 +123,7 @@ static dma_addr_t apple_dart_map(struct udevice *dev, void *addr, size_t size)
> >  	off = (phys_addr_t)addr - paddr;
> >  	psize = ALIGN(size + off, DART_PAGE_SIZE);
> >  
> > -	dva = lmb_alloc(&priv->lmb, psize, DART_PAGE_SIZE);
> > +	dva = lmb_alloc(psize, DART_PAGE_SIZE);
> >  
> >  	idx = dva / DART_PAGE_SIZE;
> >  	for (i = 0; i < psize / DART_PAGE_SIZE; i++) {
> > @@ -160,7 +159,7 @@ static void apple_dart_unmap(struct udevice *dev, dma_addr_t addr, size_t size)
> >  			   (unsigned long)&priv->l2[idx + i]);
> >  	priv->flush_tlb(priv);
> >  
> > -	lmb_free(&priv->lmb, dva, psize);
> > +	lmb_free(dva, psize);
> >  }
> >  
> >  static struct iommu_ops apple_dart_ops = {
> > @@ -213,8 +212,7 @@ static int apple_dart_probe(struct udevice *dev)
> >  	priv->dvabase = DART_PAGE_SIZE;
> >  	priv->dvaend = SZ_4G - DART_PAGE_SIZE;
> >  
> > -	lmb_init(&priv->lmb);
> > -	lmb_add(&priv->lmb, priv->dvabase, priv->dvaend - priv->dvabase);
> > +	lmb_add(priv->dvabase, priv->dvaend - priv->dvabase);
> 
> no. This breaks everything. apple_dart is an iommu and used struct lmb
> to manage the IO virtual address space. This has nothing to do
> with system memory.
> Depending on the allocation strategy this will cause all sorts of
> problems since the IO and the physical memory address space does not
> overlap on apple silicon devices. IOVA is for many devices only 32-bit
> but physical memory starts at 0x10_0000_0000 or 0x100_0000_0000.
> Every device has its own iommu / IOVA space so sharing the space between
> all of them is another problem. I'd assume only theoretical due to the
> limited driver support and memory use in u-boot.
> 
> My current plan to fix this is to resurrect the old lmb code under a
> different name.
> 
> Not sure about the same change in sandbox_iommu but I guess it could be
> ok as there is no sandbox.

Oh damn, sorry. Perhaps it can be brought back in the iommu framework
more directly? I asked Caleb and they said snapdragon doesn't need
something like this.

-- 
Tom

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