Re: [PATCH v1 1/2] physmem: Bail out qemu_ram_block_from_host() for invalid ram addrs

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

On Thu, Jul 4, 2024 at 1:26 PM Alex Bennée <alex.bennee@xxxxxxxxxx> wrote:

"Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxx> writes:

> From: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxx>
>
> Bail out in qemu_ram_block_from_host() when
> xen_ram_addr_from_mapcache() does not find an existing
> mapping.
>
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxx>
> ---
>  system/physmem.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/system/physmem.c b/system/physmem.c
> index 33d09f7571..59d1576c2b 100644
> --- a/system/physmem.c
> +++ b/system/physmem.c
> @@ -2277,6 +2277,10 @@ RAMBlock *qemu_ram_block_from_host(void *ptr, bool round_offset,
>          ram_addr_t ram_addr;
>          RCU_READ_LOCK_GUARD();
>          ram_addr = xen_ram_addr_from_mapcache(ptr);
> +        if (ram_addr == RAM_ADDR_INVALID) {
> +            return NULL;
> +        }
> +

Isn't this indicative of a failure? Should there at least be a trace
point for failed mappings?

Yes but there are already trace points for the failure cases inside xen_ram_addr_from_mapcache().

Do those address your concerns or do you think we need additional trace points?

Cheers,

Edgar

 

>          block = qemu_get_ram_block(ram_addr);
>          if (block) {
>              *offset = ram_addr - block->offset;

--
Alex Bennée
Virtualisation Tech Lead @ Linaro