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Commit da095a99 authored by Stefano Stabellini's avatar Stefano Stabellini Committed by David Vrabel
Browse files

xen/arm: introduce GNTTABOP_cache_flush 



Introduce support for new hypercall GNTTABOP_cache_flush.
Use it to perform cache flashing on pages used for dma when necessary.

If GNTTABOP_cache_flush is supported by the hypervisor, we don't need to
bounce dma map operations that involve foreign grants and non-coherent
devices.

Signed-off-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarIan Campbell <ian.campbell@citrix.com>
parent a4dba130

arch/arm/xen/mm.c

+32 −2
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 
#include <linux/swiotlb.h>



#include <xen/xen.h>

#include <xen/interface/grant_table.h>

#include <xen/interface/memory.h>

#include <xen/swiotlb-xen.h>
@@ -24,12 +25,14 @@ enum dma_cache_op { 
       DMA_UNMAP,

       DMA_MAP,

};

static bool hypercall_cflush = false;



/* functions called by SWIOTLB */



static void dma_cache_maint(dma_addr_t handle, unsigned long offset,

	size_t size, enum dma_data_direction dir, enum dma_cache_op op)

{

	struct gnttab_cache_flush cflush;

	unsigned long pfn;

	size_t left = size;
@@ -39,7 +42,26 @@ static void dma_cache_maint(dma_addr_t handle, unsigned long offset, 
	do {

		size_t len = left;

	

		/* TODO: cache flush */

		/* buffers in highmem or foreign pages cannot cross page

		 * boundaries */

		if (len + offset > PAGE_SIZE)

			len = PAGE_SIZE - offset;



		cflush.op = 0;

		cflush.a.dev_bus_addr = pfn << PAGE_SHIFT;

		cflush.offset = offset;

		cflush.length = len;



		if (op == DMA_UNMAP && dir != DMA_TO_DEVICE)

			cflush.op = GNTTAB_CACHE_INVAL;

		if (op == DMA_MAP) {

			if (dir == DMA_FROM_DEVICE)

				cflush.op = GNTTAB_CACHE_INVAL;

			else

				cflush.op = GNTTAB_CACHE_CLEAN;

		}

		if (cflush.op)

			HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);



		offset = 0;

		pfn++;
@@ -104,7 +126,7 @@ bool xen_arch_need_swiotlb(struct device *dev, 
			   unsigned long pfn,

			   unsigned long mfn)

{

	return ((pfn != mfn) && !is_device_dma_coherent(dev));

	return (!hypercall_cflush && (pfn != mfn) && !is_device_dma_coherent(dev));

}



int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
@@ -147,10 +169,18 @@ static struct dma_map_ops xen_swiotlb_dma_ops = { 


int __init xen_mm_init(void)

{

	struct gnttab_cache_flush cflush;

	if (!xen_initial_domain())

		return 0;

	xen_swiotlb_init(1, false);

	xen_dma_ops = &xen_swiotlb_dma_ops;



	cflush.op = 0;

	cflush.a.dev_bus_addr = 0;

	cflush.offset = 0;

	cflush.length = 0;

	if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)

		hypercall_cflush = true;

	return 0;

}

arch_initcall(xen_mm_init);

include/xen/interface/grant_table.h

+19 −0
Original line number Diff line number Diff line
@@ -478,6 +478,25 @@ struct gnttab_get_version { 
};

DEFINE_GUEST_HANDLE_STRUCT(gnttab_get_version);



/*

 * Issue one or more cache maintenance operations on a portion of a

 * page granted to the calling domain by a foreign domain.

 */

#define GNTTABOP_cache_flush          12

struct gnttab_cache_flush {

    union {

        uint64_t dev_bus_addr;

        grant_ref_t ref;

    } a;

    uint16_t offset;   /* offset from start of grant */

    uint16_t length;   /* size within the grant */

#define GNTTAB_CACHE_CLEAN          (1<<0)

#define GNTTAB_CACHE_INVAL          (1<<1)

#define GNTTAB_CACHE_SOURCE_GREF    (1<<31)

    uint32_t op;

};

DEFINE_GUEST_HANDLE_STRUCT(gnttab_cache_flush);



/*

 * Bitfield values for update_pin_status.flags.

 */