[Qemu-devel] Re: [PATCH 3/5] replace cpu_physical_memory_rw

[Anthony Liguori <anthony@codemonkey.ws>]

Glauber Costa wrote:
> This patch introduces a kvm version of cpu_physical_memory_rw.
> The main motivation is to bypass tcg version, which contains
> tcg-specific code, as well as data structures not used by kvm,
> such as l1_phys_map.
>
> In this patch, I'm using a runtime selection of which function
> to call, but the mid-term goal is to use function pointers in
> a way very close to which QEMUAccel used to be.
>
> Signed-off-by: Glauber Costa <glommer@redhat.com>
> ---
>  exec.c    |   13 +++++++++++--
>  kvm-all.c |   39 +++++++++++++++++++++++++++++++++++----
>  kvm.h     |    2 ++
>  3 files changed, 48 insertions(+), 6 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index 04eadfe..d5c88b1 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -2938,8 +2938,8 @@ int cpu_physical_memory_do_io(target_phys_addr_t addr, uint8_t *buf, int l, int
>
> +
> +void kvm_cpu_physical_memory_rw(target_phys_addr_t addr, uint8_t *buf,
> +                                int len, int is_write)
> +{
> +    KVMSlot *mem;
> +    KVMState *s = kvm_state;
> +    int l;
> +
> +    mem = kvm_lookup_slot(s, addr);
> +    if (!mem)
> +        return;
> +
> +    if ((mem->phys_offset & ~TARGET_PAGE_MASK) >= TLB_MMIO) {
> +        l = 0;
> +        while (len > l)
> +            l += cpu_physical_memory_do_io(addr + l, buf + l, len - l, is_write, mem->phys_offset);
> +    } else {
> +        uint8_t *uaddr = phys_ram_base + mem->phys_offset + (addr - mem->start_addr);
> +        if (!is_write)
> +            memcpy(buf, uaddr, len);
> +        else
> +            memcpy(uaddr, buf, len);
> +    }
> +}
>   

I think this is a bit optimistic.  It assumes addr..len fits entirely 
within a slot.  That's not necessarily the case though.  I think you 
should probably limit len to whatever is left in the slot, then if 
necessary, (tail) recursively call kvm_cpu_physical_memory_rw.

Regards,

Anthony Liguori