2021-09-17 13:59:04

by Jan Beulich

Subject: [PATCH v2 1/4] swiotlb-xen: ensure to issue well-formed XENMEM_exchange requests

While the hypervisor hasn't been enforcing this, we would still better
avoid issuing requests with GFNs not aligned to the requested order.
Instead of altering the value also in the call to panic(), drop it
there for being static and hence easy to determine without being part
of the panic message.

Signed-off-by: Jan Beulich <[email protected]>
---
I question how useful it is to wrap "bytes" in PAGE_ALIGN(), when it is
a multiple of a segment's size anyway (or at least was supposed to be,
prior to "swiotlb-xen: maintain slab count properly"). But that's
perhaps yet another separate patch.
---
v2: Drop logging of alignment. Wrap lines.

--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -230,10 +230,11 @@ retry:
/*
* Get IO TLB memory from any location.
*/
- start = memblock_alloc(PAGE_ALIGN(bytes), PAGE_SIZE);
+ start = memblock_alloc(PAGE_ALIGN(bytes),
+ IO_TLB_SEGSIZE << IO_TLB_SHIFT);
if (!start)
- panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
- __func__, PAGE_ALIGN(bytes), PAGE_SIZE);
+ panic("%s: Failed to allocate %lu bytes\n",
+ __func__, PAGE_ALIGN(bytes));

/*
* And replace that memory with pages under 4GB.

2021-09-18 03:56:13

by Stefano Stabellini

Subject: Re: [PATCH v2 1/4] swiotlb-xen: ensure to issue well-formed XENMEM_exchange requests

On Fri, 17 Sep 2021, Jan Beulich wrote:
> While the hypervisor hasn't been enforcing this, we would still better
> avoid issuing requests with GFNs not aligned to the requested order.
> Instead of altering the value also in the call to panic(), drop it
> there for being static and hence easy to determine without being part
> of the panic message.
>
> Signed-off-by: Jan Beulich <[email protected]>

Reviewed-by: Stefano Stabellini <[email protected]>


> ---
> I question how useful it is to wrap "bytes" in PAGE_ALIGN(), when it is
> a multiple of a segment's size anyway (or at least was supposed to be,
> prior to "swiotlb-xen: maintain slab count properly"). But that's
> perhaps yet another separate patch.
> ---
> v2: Drop logging of alignment. Wrap lines.
>
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -230,10 +230,11 @@ retry:
> /*
> * Get IO TLB memory from any location.
> */
> - start = memblock_alloc(PAGE_ALIGN(bytes), PAGE_SIZE);
> + start = memblock_alloc(PAGE_ALIGN(bytes),
> + IO_TLB_SEGSIZE << IO_TLB_SHIFT);
> if (!start)
> - panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
> - __func__, PAGE_ALIGN(bytes), PAGE_SIZE);
> + panic("%s: Failed to allocate %lu bytes\n",
> + __func__, PAGE_ALIGN(bytes));
>
> /*
> * And replace that memory with pages under 4GB.
>