Re: [PATCH] x86/hvm: Improve error information in handle_pio()

[Jan Beulich <jbeulich@suse.com>]

On 28.05.2020 15:07, Andrew Cooper wrote:
> domain_crash() should always have a message which emitted even in release
> builds, so something more useful than this is presented.
> 
>   (XEN) domain_crash called from io.c:171
>   (XEN) domain_crash called from io.c:171
>   (XEN) domain_crash called from io.c:171
>   ...
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Acked-by: Jan Beulich <jbeulich@suse.com>

> --- a/xen/arch/x86/hvm/io.c
> +++ b/xen/arch/x86/hvm/io.c
> @@ -167,7 +167,9 @@ bool handle_pio(uint16_t port, unsigned int size, int dir)
>          break;
>  
>      default:
> -        gdprintk(XENLOG_ERR, "Weird HVM ioemulation status %d.\n", rc);
> +        gprintk(XENLOG_ERR, "Unexpected PIO status %d, port %#x %s 0x%0*lx\n",
> +                rc, port, dir == IOREQ_WRITE ? "write" : "read",
> +                size * 2, data & ((1ul << (size * 8)) - 1));

I agree with Roger that potentially logging rubbish for IOREQ_READ
may be confusing, so initializing "data" might end up being better.
Perhaps simply drop (or put in a comment) the
"if ( dir == IOREQ_WRITE )" at the top of the function? (As an
aside, it's also odd for "data" to be "unsigned long" rather than
just "unsigned int" or, less preferable, "uint32_t".)

Jan