Re: [PATCH v5 6/8] xen: mapcache: Pass the ram_addr offset to xen_map_cache()

["Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxx>]

On Thu, May 16, 2024 at 1:08 AM Stefano Stabellini
<sstabellini@xxxxxxxxxx> wrote:
>
> On Fri, 3 May 2024, Edgar E. Iglesias wrote:
> > From: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxx>
> >
> > Pass the ram_addr offset to xen_map_cache.
> > This is in preparation for adding grant mappings that need
> > to compute the address within the RAMBlock.
> >
> > No functional changes.
> >
> > Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxx>
> > ---
> >  hw/xen/xen-mapcache.c         | 16 +++++++++++-----
> >  include/sysemu/xen-mapcache.h |  2 ++
> >  system/physmem.c              |  9 +++++----
> >  3 files changed, 18 insertions(+), 9 deletions(-)
> >
> > diff --git a/hw/xen/xen-mapcache.c b/hw/xen/xen-mapcache.c
> > index ec95445696..26bc38a9e3 100644
> > --- a/hw/xen/xen-mapcache.c
> > +++ b/hw/xen/xen-mapcache.c
> > @@ -167,7 +167,8 @@ 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;
> > @@ -266,6 +267,7 @@ 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,
> > @@ -337,14 +339,16 @@ 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);
> >          }
> >      }
> >
> > @@ -391,13 +395,15 @@ 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;
> >  }
> > @@ -632,7 +638,7 @@ 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(mc, entry, entry->vaddr_base,
> > -                     cache_size, address_index, false);
> > +                     cache_size, address_index, false, new_phys_addr);
>
> Everything else makes sense, but I don't understand how can it be that
> new_phys_addr is the block->offset here?
>

Agreed, this should be old_phys_addr propagated via phys_offset from
xen_add_to_physmap().
The reason this didn't have an effect here is that we currently only
use the ram_addr offset for grants,
and xen_replace_cache_entry is never called for grants. Anyway, I'll
fix this in the next version!




>
> >      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 b7847db1a2..33d09f7571 100644
> > --- a/system/physmem.c
> > +++ b/system/physmem.c
> > @@ -2231,13 +2231,14 @@ static void *qemu_ram_ptr_length(RAMBlock *block, 
> > ram_addr_t addr,
> >           */
> >          if (xen_mr_is_memory(block->mr)) {
> >              return xen_map_cache(block->mr, block->offset + addr,
> > -                                 len, lock, lock,
> > -                                 is_write);
> > +                                 len, block->offset,
> > +                                 lock, lock, is_write);
> >          }
> >
> >          block->host = xen_map_cache(block->mr, block->offset,
> > -                                    block->max_length, 1,
> > -                                    lock, is_write);
> > +                                    block->max_length,
> > +                                    block->offset,
> > +                                    1, lock, is_write);
> >      }
>
> This is OK but it is really making it clear that there is a mistake in
> the code. OK for now but it is something to fix in the future.
>
>
> >      return ramblock_ptr(block, addr);
> > --
> > 2.40.1
> >