[Qemu-devel] Re: [PATCH] remove smaller slots if registering a bigger one

[Jan Kiszka <jan.kiszka@siemens.com>]

Glauber Costa wrote:
> It's like a shark eating a bunch of small fishes:
> in some situations (vga linear frame buffer mapping,
> for example), we need to register a new slot in place
> of older, smaller ones. This patch handles this case
> 
> Signed-off-by: Glauber Costa <glommer@redhat.com>
> ---
>  kvm-all.c |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)
> 
> diff --git a/kvm-all.c b/kvm-all.c
> index 9fb295c..53aca0a 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -582,6 +582,16 @@ void kvm_set_phys_mem(target_phys_addr_t start_addr,
>                  kvm_set_phys_mem(mem_start, mem_size, mem_offset);
>  
>              return;
> +        } else if (start_addr <= mem->start_addr &&
> +                   (start_addr + size) >= (mem->start_addr +
> +                                           mem->memory_size)) {
> +            KVMSlot slot;
> +            /* unregister whole slot */
> +            memcpy(&slot, mem, sizeof(slot));
> +            mem->memory_size = 0;
> +            kvm_set_user_memory_region(s, mem);
> +
> +            kvm_set_phys_mem(start_addr, size, phys_offset);

That may solve some problems, but...

>          } else {
>              printf("Registering overlapping slot\n");
>              abort();
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...as long as this line exists, issues will remain. IIRC, the mapping
the i440 tries to re-establish after reboot will hit this case.


BTW, I found the unposted patch below in my attic, maybe you can comment
on it (if it makes sense, I'll properly repost with signed-off).

Thanks,
Jan

---------->

kvm: cleanup unmap condition in kvm_set_phys_mem
    
Testing for TLB_MMIO on unmap makes no sense as A) that flag belongs to
CPUTLBEntry and not to io_memory slots or physical addresses and B) we
already use a different condition before mapping. So make this test
consistent.

diff --git a/kvm-all.c b/kvm-all.c
index 9fb295c..c0481a0 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -540,7 +540,7 @@ void kvm_set_phys_mem(target_phys_addr_t start_addr,
 
     mem = kvm_lookup_slot(s, start_addr);
     if (mem) {
-        if ((flags == IO_MEM_UNASSIGNED) || (flags >= TLB_MMIO)) {
+        if (flags >= IO_MEM_UNASSIGNED) {
             mem->memory_size = 0;
             mem->start_addr = start_addr;
             mem->phys_offset = 0;