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[Qemu-devel] [PATCH 2/8] exec: make qemu_ram_ptr_length more similar to
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 2/8] exec: make qemu_ram_ptr_length more similar to qemu_get_ram_ptr |
Date: |
Wed, 16 Dec 2015 11:59:54 +0100 |
Notably, use qemu_get_ram_block to enjoy the MRU optimization.
Signed-off-by: Paolo Bonzini <address@hidden>
---
exec.c | 46 +++++++++++++++++++++++-----------------------
1 file changed, 23 insertions(+), 23 deletions(-)
diff --git a/exec.c b/exec.c
index 1a5ea1f..026a9f2 100644
--- a/exec.c
+++ b/exec.c
@@ -1836,36 +1836,33 @@ void *qemu_get_ram_ptr(ram_addr_t addr)
/* Return a host pointer to guest's ram. Similar to qemu_get_ram_ptr
* but takes a size argument.
*
- * By the time this function returns, the returned pointer is not protected
- * by RCU anymore. If the caller is not within an RCU critical section and
- * does not hold the iothread lock, it must have other means of protecting the
- * pointer, such as a reference to the region that includes the incoming
- * ram_addr_t.
+ * Called within RCU critical section.
*/
static void *qemu_ram_ptr_length(ram_addr_t addr, hwaddr *size)
{
- void *ptr;
+ RAMBlock *block;
+ ram_addr_t offset_inside_block;
if (*size == 0) {
return NULL;
}
- if (xen_enabled()) {
- return xen_map_cache(addr, *size, 1);
- } else {
- RAMBlock *block;
- rcu_read_lock();
- QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
- if (addr - block->offset < block->max_length) {
- if (addr - block->offset + *size > block->max_length)
- *size = block->max_length - addr + block->offset;
- ptr = ramblock_ptr(block, addr - block->offset);
- rcu_read_unlock();
- return ptr;
- }
+
+ block = qemu_get_ram_block(addr);
+ offset_inside_block = addr - block->offset;
+ *size = MIN(*size, block->max_length - offset_inside_block);
+
+ if (xen_enabled() && block->host == NULL) {
+ /* We need to check if the requested address is in the RAM
+ * because we don't want to map the entire memory in QEMU.
+ * In that case just map the requested area.
+ */
+ if (block->offset == 0) {
+ return xen_map_cache(addr, *size, 1);
}
- fprintf(stderr, "Bad ram offset %" PRIx64 "\n", (uint64_t)addr);
- abort();
+ block->host = xen_map_cache(block->offset, block->max_length, 1);
}
+
+ return ramblock_ptr(block, offset_inside_block);
}
/*
@@ -2813,6 +2810,7 @@ void *address_space_map(AddressSpace *as,
hwaddr l, xlat, base;
MemoryRegion *mr, *this_mr;
ram_addr_t raddr;
+ void *ptr;
if (len == 0) {
return NULL;
@@ -2864,9 +2862,11 @@ void *address_space_map(AddressSpace *as,
}
memory_region_ref(mr);
- rcu_read_unlock();
*plen = done;
- return qemu_ram_ptr_length(raddr + base, plen);
+ ptr = qemu_ram_ptr_length(raddr + base, plen);
+ rcu_read_unlock();
+
+ return ptr;
}
/* Unmaps a memory region previously mapped by address_space_map().
--
2.5.0
- [Qemu-devel] [PATCH 0/8] Optimize address_space_read/write/map, Paolo Bonzini, 2015/12/16
- [Qemu-devel] [PATCH 3/8] memory: reorder MemoryRegion fields, Paolo Bonzini, 2015/12/16
- [Qemu-devel] [PATCH 5/8] memory: split address_space_read and address_space_write, Paolo Bonzini, 2015/12/16
- [Qemu-devel] [PATCH 1/8] exec: always call qemu_get_ram_ptr within rcu_read_lock, Paolo Bonzini, 2015/12/16
- [Qemu-devel] [PATCH 4/8] memory: avoid unnecessary object_ref/unref, Paolo Bonzini, 2015/12/16
- [Qemu-devel] [PATCH 2/8] exec: make qemu_ram_ptr_length more similar to qemu_get_ram_ptr,
Paolo Bonzini <=
- [Qemu-devel] [PATCH 8/8] memory: try to inline constant-length reads, Paolo Bonzini, 2015/12/16
- [Qemu-devel] [PATCH 6/8] memory: extract first iteration of address_space_read and address_space_write, Paolo Bonzini, 2015/12/16
- [Qemu-devel] [PATCH] memory: try to inline constant-length reads, Paolo Bonzini, 2015/12/16
- [Qemu-devel] [PATCH 7/8] memory: inline a few small accessors, Paolo Bonzini, 2015/12/16