Re: [PATCH] remoteproc: qcom_q6v5_mss: map/unmap metadata region before/after use

[Sibi Sankar <quic_sibis@xxxxxxxxxxx>]

Hey Matthias,
Thanks for taking time to review the patch.

On 5/6/22 11:37 PM, Matthias Kaehlcke wrote:
> On Fri, May 06, 2022 at 07:21:26PM +0530, Sibi Sankar wrote:
> > The application processor accessing the dynamically assigned metadata
> > region after assigning it to the remote Q6 would lead to an XPU violation.
> > Fix this by un-mapping the metadata region post firmware header copy. The
> > metadata region is freed only after the modem Q6 is done with fw header
> > authentication.
> >
> > Signed-off-by: Sibi Sankar <quic_sibis@xxxxxxxxxxx>
>
> Should this have a 'Fixes:' tag
It ideally should have but similar to what we did for mba and mpss
region map/unmap, it would be a ugly backport since it would point to
the very first commit. We can agree to do a backport if it's ever
reported upstream on any of the older SoCs.

-Sibi

> > ---
> >   drivers/remoteproc/qcom_q6v5_mss.c | 43 +++++++++++++++++++++++++++++++-------
> >   1 file changed, 35 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/remoteproc/qcom_q6v5_mss.c b/drivers/remoteproc/qcom_q6v5_mss.c
> > index af217de75e4d..eb34a258b67b 100644
> > --- a/drivers/remoteproc/qcom_q6v5_mss.c
> > +++ b/drivers/remoteproc/qcom_q6v5_mss.c
> > @@ -10,6 +10,7 @@
> >   #include <linux/clk.h>
> >   #include <linux/delay.h>
> >   #include <linux/devcoredump.h>
> > +#include <linux/dma-map-ops.h>
> >   #include <linux/dma-mapping.h>
> >   #include <linux/interrupt.h>
> >   #include <linux/kernel.h>
> > @@ -932,27 +933,52 @@ static void q6v5proc_halt_axi_port(struct q6v5 *qproc,
> >   static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
> >   				const char *fw_name)
> >   {
> > -	unsigned long dma_attrs = DMA_ATTR_FORCE_CONTIGUOUS;
> > +	unsigned long dma_attrs = DMA_ATTR_FORCE_CONTIGUOUS | DMA_ATTR_NO_KERNEL_MAPPING;
> > +	unsigned long flags = VM_DMA_COHERENT | VM_FLUSH_RESET_PERMS;
> > +	struct page **pages;
> > +	struct page *page;
> >   	dma_addr_t phys;
> >   	void *metadata;
> >   	int mdata_perm;
> >   	int xferop_ret;
> >   	size_t size;
> > -	void *ptr;
> > +	void *vaddr;
> > +	int count;
> >   	int ret;
> > +	int i;
> >   
> >   	metadata = qcom_mdt_read_metadata(fw, &size, fw_name, qproc->dev);
> >   	if (IS_ERR(metadata))
> >   		return PTR_ERR(metadata);
> >   
> > -	ptr = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
> > -	if (!ptr) {
> > -		kfree(metadata);
> > +	page = dma_alloc_attrs(qproc->dev, size, &phys, GFP_KERNEL, dma_attrs);
> > +	if (!page) {
> >   		dev_err(qproc->dev, "failed to allocate mdt buffer\n");
> > -		return -ENOMEM;
> > +		ret = -ENOMEM;
> > +		goto free_metadata;
> > +	}
> > +
> > +	count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> > +	pages = kmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
> > +	if (!pages) {
> > +		ret = -ENOMEM;
> > +		goto free_metadata;
> >   	}
> >   
> > -	memcpy(ptr, metadata, size);
> > +	for (i = 0; i < count; i++)
> > +		pages[i] = nth_page(page, i);
> > +
> > +	vaddr = vmap(pages, count, flags, dma_pgprot(qproc->dev, PAGE_KERNEL, dma_attrs));
> > +	kfree(pages);
> > +	if (!vaddr) {
> > +		dev_err(qproc->dev, "unable to map memory region: %pa+%zx\n", &phys, size);
> > +		ret = -EBUSY;
> > +		goto free_metadata;
> > +	}
> > +
> > +	memcpy(vaddr, metadata, size);
> > +
> > +	vunmap(vaddr);
> >   
> >   	/* Hypervisor mapping to access metadata by modem */
> >   	mdata_perm = BIT(QCOM_SCM_VMID_HLOS);
> > @@ -982,7 +1008,8 @@ static int q6v5_mpss_init_image(struct q6v5 *qproc, const struct firmware *fw,
> >   			 "mdt buffer not reclaimed system may become unstable\n");
> >   
> >   free_dma_attrs:
> > -	dma_free_attrs(qproc->dev, size, ptr, phys, dma_attrs);
> > +	dma_free_attrs(qproc->dev, size, page, phys, dma_attrs);
> > +free_metadata:
> >   	kfree(metadata);
> >   
> >   	return ret < 0 ? ret : 0;
> > --
> > 2.7.4