On Tue, 30 Apr 2024, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.igles...@amd.com>
>
> The current mapcache assumes that all memory is mapped
> in a single RAM MR (the first one with offset 0). Remove
> this assumption and propagate the offset to the mapcache
> so it can do reverse mappings (from hostptr -> ram_addr).
>
> This is in preparation for adding grant mappings.
>
> Signed-off-by: Edgar E. Iglesias <edgar.igles...@amd.com>
Looking at xen_remap_bucket, it is only using address_index (without
adding ram_offset) to map foreign memory. From xen_remap_bucket, I would
understand that address_index already includes the ram_offset.
Meaning that if we want to map foreign mapping at address 0x5000, then
address_index would be 0x5000, even if ram_offset is 0x1000.
But then looking xen_ram_addr_from_mapcache_single ram_offset is added
to paddr_index to calculate the physical address. So in that case we
would want address_index to be 0x4000 and ram_offset to be 0x1000. But
xen_remap_bucket would have to sum address_index and ram_offset to map
foreign memory.
So I am a bit confused, did I get it wrong? One more comment below.
> ---
> hw/xen/xen-mapcache.c | 25 ++++++++++++++++++-------
> include/sysemu/xen-mapcache.h | 2 ++
> system/physmem.c | 8 ++++----
> 3 files changed, 24 insertions(+), 11 deletions(-)
>
> diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
> index 09b5f36d9c..1b32d0c003 100644
> --- a/hw/xen/xen-mapcache.c
> +++ b/hw/xen/xen-mapcache.c
> @@ -43,6 +43,9 @@ typedef struct MapCacheEntry {
> #define XEN_MAPCACHE_ENTRY_DUMMY (1 << 0)
> uint8_t flags;
> hwaddr size;
> +
> + /* Keep ram_addr offset for reverse mappings (hostptr -> ram_addr). */
> + ram_addr_t ram_offset;
> struct MapCacheEntry *next;
> } MapCacheEntry;
>
> @@ -165,7 +168,8 @@ static void xen_remap_bucket(MapCache *mc,
> void *vaddr,
> hwaddr size,
> hwaddr address_index,
> - bool dummy)
> + bool dummy,
> + ram_addr_t ram_offset)
> {
> uint8_t *vaddr_base;
> xen_pfn_t *pfns;
> @@ -244,6 +248,7 @@ static void xen_remap_bucket(MapCache *mc,
> entry->size = size;
> entry->valid_mapping = g_new0(unsigned long,
> BITS_TO_LONGS(size >> XC_PAGE_SHIFT));
> + entry->ram_offset = ram_offset;
>
> if (dummy) {
> entry->flags |= XEN_MAPCACHE_ENTRY_DUMMY;
> @@ -264,6 +269,7 @@ static void xen_remap_bucket(MapCache *mc,
>
> static uint8_t *xen_map_cache_unlocked(MapCache *mc,
> hwaddr phys_addr, hwaddr size,
> + ram_addr_t ram_offset,
> uint8_t lock, bool dma, bool is_write)
> {
> MapCacheEntry *entry, *pentry = NULL,
> @@ -335,14 +341,16 @@ tryagain:
> if (!entry) {
> entry = g_new0(MapCacheEntry, 1);
> pentry->next = entry;
> - xen_remap_bucket(mc, entry, NULL, cache_size, address_index, dummy);
> + xen_remap_bucket(mc, entry, NULL, cache_size, address_index, dummy,
> + ram_offset);
> } else if (!entry->lock) {
> if (!entry->vaddr_base || entry->paddr_index != address_index ||
> entry->size != cache_size ||
> !test_bits(address_offset >> XC_PAGE_SHIFT,
> test_bit_size >> XC_PAGE_SHIFT,
> entry->valid_mapping)) {
> - xen_remap_bucket(mc, entry, NULL, cache_size, address_index,
> dummy);
> + xen_remap_bucket(mc, entry, NULL, cache_size, address_index,
> dummy,
> + ram_offset);
> }
> }
>
> @@ -389,13 +397,15 @@ tryagain:
>
> uint8_t *xen_map_cache(MemoryRegion *mr,
> hwaddr phys_addr, hwaddr size,
> + ram_addr_t ram_addr_offset,
> uint8_t lock, bool dma,
> bool is_write)
> {
> uint8_t *p;
>
> mapcache_lock(mapcache);
> - p = xen_map_cache_unlocked(mapcache, phys_addr, size, lock, dma,
> is_write);
> + p = xen_map_cache_unlocked(mapcache, phys_addr, size, ram_addr_offset,
> + lock, dma, is_write);
> mapcache_unlock(mapcache);
> return p;
> }
> @@ -432,7 +442,8 @@ static ram_addr_t
> xen_ram_addr_from_mapcache_single(MapCache *mc, void *ptr)
> raddr = RAM_ADDR_INVALID;
> } else {
> raddr = (reventry->paddr_index << mc->bucket_shift) +
> - ((unsigned long) ptr - (unsigned long) entry->vaddr_base);
> + ((unsigned long) ptr - (unsigned long) entry->vaddr_base) +
> + entry->ram_offset;
> }
> mapcache_unlock(mc);
> return raddr;
> @@ -627,8 +638,8 @@ static uint8_t *xen_replace_cache_entry_unlocked(MapCache
> *mc,
>
> trace_xen_replace_cache_entry_dummy(old_phys_addr, new_phys_addr);
>
> - xen_remap_bucket(mapcache, entry, entry->vaddr_base,
> - cache_size, address_index, false);
> + xen_remap_bucket(mc, entry, entry->vaddr_base,
> + cache_size, address_index, false, entry->ram_offset);
> if (!test_bits(address_offset >> XC_PAGE_SHIFT,
> test_bit_size >> XC_PAGE_SHIFT,
> entry->valid_mapping)) {
> diff --git a/include/sysemu/xen-mapcache.h b/include/sysemu/xen-mapcache.h
> index 1ec9e66752..b5e3ea1bc0 100644
> --- a/include/sysemu/xen-mapcache.h
> +++ b/include/sysemu/xen-mapcache.h
> @@ -19,6 +19,7 @@ typedef hwaddr (*phys_offset_to_gaddr_t)(hwaddr phys_offset,
> void xen_map_cache_init(phys_offset_to_gaddr_t f,
> void *opaque);
> uint8_t *xen_map_cache(MemoryRegion *mr, hwaddr phys_addr, hwaddr size,
> + ram_addr_t ram_addr_offset,
> uint8_t lock, bool dma,
> bool is_write);
> ram_addr_t xen_ram_addr_from_mapcache(void *ptr);
> @@ -37,6 +38,7 @@ static inline void
> xen_map_cache_init(phys_offset_to_gaddr_t f,
> static inline uint8_t *xen_map_cache(MemoryRegion *mr,
> hwaddr phys_addr,
> hwaddr size,
> + ram_addr_t ram_addr_offset,
> uint8_t lock,
> bool dma,
> bool is_write)
> diff --git a/system/physmem.c b/system/physmem.c
> index 1a5ffcba2a..5b16eeccca 100644
> --- a/system/physmem.c
> +++ b/system/physmem.c
> @@ -2228,13 +2228,13 @@ static void *qemu_ram_ptr_length(RAMBlock *block,
> ram_addr_t addr,
> * In that case just map the requested area.
> */
> if (xen_mr_is_memory(block->mr)) {
> - return xen_map_cache(block->mr, addr, len, lock, lock,
> - is_write);
> + return xen_map_cache(block->mr, addr, len, block->offset,
> + lock, lock, is_write);
Have you considered not tracking offset and address separately and
simply do this?
return xen_map_cache(block->mr, addr + block->offset, len,
lock, lock, is_write);
> }
>
> block->host = xen_map_cache(block->mr, block->offset,
> - block->max_length, 1,
> - lock, is_write);
> + block->max_length, 0,
> + 1, lock, is_write);
> }
>
> return ramblock_ptr(block, addr);
> --
> 2.40.1
>
