From 1ff7c5986a515d2d936eba026ff19947bbc7cb92 Mon Sep 17 00:00:00 2001 From: Stefano Stabellini Date: Wed, 3 May 2017 14:00:35 -0700 Subject: xen/mapcache: store dma information in revmapcache entries for debugging The Xen mapcache is able to create long term mappings, they are called "locked" mappings. The third parameter of the xen_map_cache call specifies if a mapping is a "locked" mapping. >From the QEMU point of view there are two kinds of long term mappings: [a] device memory mappings, such as option roms and video memory [b] dma mappings, created by dma_memory_map & friends After certain operations, ballooning a VM in particular, Xen asks QEMU kindly to destroy all mappings. However, certainly [a] mappings are present and cannot be removed. That's not a problem as they are not affected by balloonning. The *real* problem is that if there are any mappings of type [b], any outstanding dma operations could fail. This is a known shortcoming. In other words, when Xen asks QEMU to destroy all mappings, it is an error if any [b] mappings exist. However today we have no way of distinguishing [a] from [b]. Because of that, we cannot even print a decent warning. This patch introduces a new "dma" bool field to MapCacheRev entires, to remember if a given mapping is for dma or is a long term device memory mapping. When xen_invalidate_map_cache is called, we print a warning if any [b] mappings exist. We ignore [a] mappings. Mappings created by qemu_map_ram_ptr are assumed to be [a], while mappings created by address_space_map->qemu_ram_ptr_length are assumed to be [b]. The goal of the patch is to make debugging and system understanding easier. Signed-off-by: Stefano Stabellini Acked-by: Paolo Bonzini Acked-by: Anthony PERARD --- include/sysemu/xen-mapcache.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/sysemu/xen-mapcache.h b/include/sysemu/xen-mapcache.h index b8c93b9bce..01daaad00c 100644 --- a/include/sysemu/xen-mapcache.h +++ b/include/sysemu/xen-mapcache.h @@ -17,7 +17,7 @@ typedef hwaddr (*phys_offset_to_gaddr_t)(hwaddr start_addr, void xen_map_cache_init(phys_offset_to_gaddr_t f, void *opaque); uint8_t *xen_map_cache(hwaddr phys_addr, hwaddr size, - uint8_t lock); + uint8_t lock, bool dma); ram_addr_t xen_ram_addr_from_mapcache(void *ptr); void xen_invalidate_map_cache_entry(uint8_t *buffer); void xen_invalidate_map_cache(void); @@ -31,7 +31,8 @@ static inline void xen_map_cache_init(phys_offset_to_gaddr_t f, static inline uint8_t *xen_map_cache(hwaddr phys_addr, hwaddr size, - uint8_t lock) + uint8_t lock, + bool dma) { abort(); } -- cgit v1.2.3