| Message ID | alpine.DEB.2.10.1705031359390.9240@sstabellini-ThinkPad-X260 (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, May 03, 2017 at 02:00:35PM -0700, Stefano Stabellini wrote: > 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 <sstabellini@kernel.org> > Acked-by: Paolo Bonzini <pbonzini@redhat.com> > Acked-by: Anthony PERARD <anthony.perard@citrix.com> > --- > > Changes in v2: > - add acked-by > - fix code style problem > > diff --git a/exec.c b/exec.c > index eac6085..85769e1 100644 > --- a/exec.c > +++ b/exec.c > @@ -2084,10 +2084,10 @@ void *qemu_map_ram_ptr(RAMBlock *ram_block, ram_addr_t addr) > * In that case just map until the end of the page. > */ > if (block->offset == 0) { > - return xen_map_cache(addr, 0, 0); > + return xen_map_cache(addr, 0, 0, false); > } > > - block->host = xen_map_cache(block->offset, block->max_length, 1); > + block->host = xen_map_cache(block->offset, block->max_length, 1, false); > } > return ramblock_ptr(block, addr); > } > @@ -2117,10 +2117,10 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_block, ram_addr_t addr, > * In that case just map the requested area. > */ > if (block->offset == 0) { > - return xen_map_cache(addr, *size, 1); > + return xen_map_cache(addr, *size, 1, true); > } > > - block->host = xen_map_cache(block->offset, block->max_length, 1); > + block->host = xen_map_cache(block->offset, block->max_length, 1, true); > } > > return ramblock_ptr(block, addr); > diff --git a/hw/i386/xen/xen-mapcache.c b/hw/i386/xen/xen-mapcache.c > index 31debdf..e60156c 100644 > --- a/hw/i386/xen/xen-mapcache.c > +++ b/hw/i386/xen/xen-mapcache.c > @@ -62,6 +62,7 @@ typedef struct MapCacheRev { > hwaddr paddr_index; > hwaddr size; > QTAILQ_ENTRY(MapCacheRev) next; > + bool dma; > } MapCacheRev; > > typedef struct MapCache { > @@ -202,7 +203,7 @@ static void xen_remap_bucket(MapCacheEntry *entry, > } > > static uint8_t *xen_map_cache_unlocked(hwaddr phys_addr, hwaddr size, > - uint8_t lock) > + uint8_t lock, bool dma) > { > MapCacheEntry *entry, *pentry = NULL; > hwaddr address_index; > @@ -289,6 +290,7 @@ tryagain: > if (lock) { > MapCacheRev *reventry = g_malloc0(sizeof(MapCacheRev)); > entry->lock++; > + reventry->dma = dma; > reventry->vaddr_req = mapcache->last_entry->vaddr_base + address_offset; > reventry->paddr_index = mapcache->last_entry->paddr_index; > reventry->size = entry->size; > @@ -300,12 +302,12 @@ tryagain: > } > > uint8_t *xen_map_cache(hwaddr phys_addr, hwaddr size, > - uint8_t lock) > + uint8_t lock, bool dma) > { > uint8_t *p; > > mapcache_lock(); > - p = xen_map_cache_unlocked(phys_addr, size, lock); > + p = xen_map_cache_unlocked(phys_addr, size, lock, dma); > mapcache_unlock(); > return p; > } > @@ -426,8 +428,11 @@ void xen_invalidate_map_cache(void) > mapcache_lock(); > > QTAILQ_FOREACH(reventry, &mapcache->locked_entries, next) { > - DPRINTF("There should be no locked mappings at this time, " > - "but "TARGET_FMT_plx" -> %p is present\n", > + if (!reventry->dma) { > + continue; > + } > + fprintf(stderr, "Locked DMA mapping while invalidating mapcache!" > + " "TARGET_FMT_plx" -> %p is present\n", > reventry->paddr_index, reventry->vaddr_req); > } > > diff --git a/include/sysemu/xen-mapcache.h b/include/sysemu/xen-mapcache.h > index b8c93b9..01daaad 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(); > }
diff --git a/exec.c b/exec.c index eac6085..85769e1 100644 --- a/exec.c +++ b/exec.c @@ -2084,10 +2084,10 @@ void *qemu_map_ram_ptr(RAMBlock *ram_block, ram_addr_t addr) * In that case just map until the end of the page. */ if (block->offset == 0) { - return xen_map_cache(addr, 0, 0); + return xen_map_cache(addr, 0, 0, false); } - block->host = xen_map_cache(block->offset, block->max_length, 1); + block->host = xen_map_cache(block->offset, block->max_length, 1, false); } return ramblock_ptr(block, addr); } @@ -2117,10 +2117,10 @@ static void *qemu_ram_ptr_length(RAMBlock *ram_block, ram_addr_t addr, * In that case just map the requested area. */ if (block->offset == 0) { - return xen_map_cache(addr, *size, 1); + return xen_map_cache(addr, *size, 1, true); } - block->host = xen_map_cache(block->offset, block->max_length, 1); + block->host = xen_map_cache(block->offset, block->max_length, 1, true); } return ramblock_ptr(block, addr); diff --git a/hw/i386/xen/xen-mapcache.c b/hw/i386/xen/xen-mapcache.c index 31debdf..e60156c 100644 --- a/hw/i386/xen/xen-mapcache.c +++ b/hw/i386/xen/xen-mapcache.c @@ -62,6 +62,7 @@ typedef struct MapCacheRev { hwaddr paddr_index; hwaddr size; QTAILQ_ENTRY(MapCacheRev) next; + bool dma; } MapCacheRev; typedef struct MapCache { @@ -202,7 +203,7 @@ static void xen_remap_bucket(MapCacheEntry *entry, } static uint8_t *xen_map_cache_unlocked(hwaddr phys_addr, hwaddr size, - uint8_t lock) + uint8_t lock, bool dma) { MapCacheEntry *entry, *pentry = NULL; hwaddr address_index; @@ -289,6 +290,7 @@ tryagain: if (lock) { MapCacheRev *reventry = g_malloc0(sizeof(MapCacheRev)); entry->lock++; + reventry->dma = dma; reventry->vaddr_req = mapcache->last_entry->vaddr_base + address_offset; reventry->paddr_index = mapcache->last_entry->paddr_index; reventry->size = entry->size; @@ -300,12 +302,12 @@ tryagain: } uint8_t *xen_map_cache(hwaddr phys_addr, hwaddr size, - uint8_t lock) + uint8_t lock, bool dma) { uint8_t *p; mapcache_lock(); - p = xen_map_cache_unlocked(phys_addr, size, lock); + p = xen_map_cache_unlocked(phys_addr, size, lock, dma); mapcache_unlock(); return p; } @@ -426,8 +428,11 @@ void xen_invalidate_map_cache(void) mapcache_lock(); QTAILQ_FOREACH(reventry, &mapcache->locked_entries, next) { - DPRINTF("There should be no locked mappings at this time, " - "but "TARGET_FMT_plx" -> %p is present\n", + if (!reventry->dma) { + continue; + } + fprintf(stderr, "Locked DMA mapping while invalidating mapcache!" + " "TARGET_FMT_plx" -> %p is present\n", reventry->paddr_index, reventry->vaddr_req); } diff --git a/include/sysemu/xen-mapcache.h b/include/sysemu/xen-mapcache.h index b8c93b9..01daaad 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(); }