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swiotlb-xen: this is PV-only on x86 

The code is unreachable for HVM or PVH, and it also makes little sense
in auto-translated environments. On Arm, with
xen_{create,destroy}_contiguous_region() both being stubs, I have a hard
time seeing what good the Xen specific variant does - the generic one
ought to be fine for all purposes there. Still Arm code explicitly
references symbols here, so the code will continue to be included there.

Instead of making PCI_XEN's "select" conditional, simply drop it -
SWIOTLB_XEN will be available unconditionally in the PV case anyway, and
is - as explained above - dead code in non-PV environments.

This in turn allows dropping the stubs for
xen_{create,destroy}_contiguous_region(), the former of which was broken
anyway - it failed to set the DMA handle output.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

Link: https://lore.kernel.org/r/5947b8ae-fdc7-225c-4838-84712265fc1e@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Jan Beulich 2021-09-17 12:50:38 +02:00 committed by Juergen Gross
parent 8e1034a526
commit 794d5b8a49
3 changed files with 1 additions and 13 deletions
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1
arch/x86/Kconfig
View File

@ -2605,7 +2605,6 @@ config PCI_OLPC
config PCI_XEN
def_bool y
depends on PCI && XEN
select SWIOTLB_XEN
config MMCONF_FAM10H
def_bool y

1
drivers/xen/Kconfig
View File

@ -177,6 +177,7 @@ config XEN_GRANT_DMA_ALLOC
config SWIOTLB_XEN
def_bool y
depends on XEN_PV || ARM || ARM64
select DMA_OPS
select SWIOTLB

12
include/xen/xen-ops.h
View File

@ -46,19 +46,7 @@ extern unsigned long *xen_contiguous_bitmap;
int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
unsigned int address_bits,
dma_addr_t *dma_handle);
void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order);
#else
static inline int xen_create_contiguous_region(phys_addr_t pstart,
unsigned int order,
unsigned int address_bits,
dma_addr_t *dma_handle)
{
return 0;
}
static inline void xen_destroy_contiguous_region(phys_addr_t pstart,
unsigned int order) { }
#endif
#if defined(CONFIG_XEN_PV)