2021-05-11 17:44:03

by Stefano Stabellini

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

From: Stefano Stabellini <[email protected]>

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: [email protected]
CC: [email protected]
Signed-off-by: Stefano Stabellini <[email protected]>
---
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

2021-05-11 23:40:04

by Boris Ostrovsky

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

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 <[email protected]>

2021-05-12 20:38:00

by Stefano Stabellini

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

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 <[email protected]>

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