[PATCH 2/2] xen/swiotlb: check if the swiotlb has already been initialized

[PATCH 2/2] xen/swiotlb: check if the swiotlb has already been initialized

[Stefano Stabellini]

From: Stefano Stabellini <stefano.stabellini@xilinx.com>

xen_swiotlb_init calls swiotlb_late_init_with_tbl, which fails with
-ENOMEM if the swiotlb has already been initialized.

Add an explicit check io_tlb_default_mem != NULL at the beginning of
xen_swiotlb_init. If the swiotlb is already initialized print a warning
and return -EEXIST.

On x86, the error propagates.

On ARM, we don't actually need a special swiotlb buffer (yet), any
buffer would do. So ignore the error and continue.

CC: boris.ostrovsky@oracle.com
CC: jgross@suse.com
Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
---
 arch/arm/xen/mm.c         | 8 +++++++-
 drivers/xen/swiotlb-xen.c | 5 +++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index 223b1151fd7d..a7e54a087b80 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -138,9 +138,15 @@ void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
 static int __init xen_mm_init(void)
 {
 	struct gnttab_cache_flush cflush;
+	int rc;
+
 	if (!xen_swiotlb_detect())
 		return 0;
-	xen_swiotlb_init();
+
+	rc = xen_swiotlb_init();
+	/* we can work with the default swiotlb */
+	if (rc < 0 && rc != -EEXIST)
+		return rc;
 
 	cflush.op = 0;
 	cflush.a.dev_bus_addr = 0;
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 4c89afc0df62..6412d59ce7f8 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -164,6 +164,11 @@ int __ref xen_swiotlb_init(void)
 	int rc = -ENOMEM;
 	char *start;
 
+	if (io_tlb_default_mem != NULL) {
+		printk(KERN_WARNING "Xen-SWIOTLB: swiotlb buffer already initialized\n");
+		return -EEXIST;
+	}
+
 retry:
 	m_ret = XEN_SWIOTLB_ENOMEM;
 	order = get_order(bytes);
-- 
2.17.1

Re: [PATCH 2/2] xen/swiotlb: check if the swiotlb has already been initialized

[Boris Ostrovsky]

On 5/11/21 1:41 PM, Stefano Stabellini wrote:
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -164,6 +164,11 @@ int __ref xen_swiotlb_init(void)
>  	int rc = -ENOMEM;
>  	char *start;
>  
> +	if (io_tlb_default_mem != NULL) {
> +		printk(KERN_WARNING "Xen-SWIOTLB: swiotlb buffer already initialized\n");


pr_warn().


Reviewed-by: Boris Ostrovsky <boris.ostrvsky@oracle.com>

Re: [PATCH 2/2] xen/swiotlb: check if the swiotlb has already been initialized

[Stefano Stabellini]

On Tue, 11 May 2021, Boris Ostrovsky wrote:
> On 5/11/21 1:41 PM, Stefano Stabellini wrote:
> > --- a/drivers/xen/swiotlb-xen.c
> > +++ b/drivers/xen/swiotlb-xen.c
> > @@ -164,6 +164,11 @@ int __ref xen_swiotlb_init(void)
> >  	int rc = -ENOMEM;
> >  	char *start;
> >  
> > +	if (io_tlb_default_mem != NULL) {
> > +		printk(KERN_WARNING "Xen-SWIOTLB: swiotlb buffer already initialized\n");
> 
> 
> pr_warn().
> 
> 
> Reviewed-by: Boris Ostrovsky <boris.ostrvsky@oracle.com>

Thank you! I'll send a v2 shortly with the change to pr_warn and your
reviewed-by.

Re: [PATCH 2/2] xen/swiotlb: check if the swiotlb has already been initialized

[Stefano Stabellini]

On Tue, 11 May 2021, Boris Ostrovsky wrote:
> On 5/11/21 1:41 PM, Stefano Stabellini wrote:
> > --- a/drivers/xen/swiotlb-xen.c
> > +++ b/drivers/xen/swiotlb-xen.c
> > @@ -164,6 +164,11 @@ int __ref xen_swiotlb_init(void)
> >  	int rc = -ENOMEM;
> >  	char *start;
> >  
> > +	if (io_tlb_default_mem != NULL) {
> > +		printk(KERN_WARNING "Xen-SWIOTLB: swiotlb buffer already initialized\n");
> 
> 
> pr_warn().
> 
> 
> Reviewed-by: Boris Ostrovsky <boris.ostrvsky@oracle.com>

Thank you! I'll send a v2 shortly with the change to pr_warn and your
reviewed-by.