Re: [Xen-devel] [PATCH v2] nested VMX: fix I/O port exit emulation

["Egger, Christoph" <chegger@xxxxxxxxx>]

On 03.12.13 15:06, Jan Beulich wrote:
> For multi-byte operations all affected ports' bits in the bitmap need
> to be checked, not just the first port's one.
> 
> Reported-by: Matthew Daley <mattd@xxxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> ---
> v2: Fix loop construct.
> 
> --- a/xen/arch/x86/hvm/vmx/vvmx.c
> +++ b/xen/arch/x86/hvm/vmx/vvmx.c
> @@ -2134,7 +2134,6 @@ int nvmx_n2_vmexit_handler(struct cpu_us
>      struct nestedvcpu *nvcpu = &vcpu_nestedhvm(v);
>      struct nestedvmx *nvmx = &vcpu_2_nvmx(v);
>      u32 ctrl;
> -    u8 *bitmap;
>  
>      nvcpu->nv_vmexit_pending = 0;
>      nvmx->intr.intr_info = 0;
> @@ -2220,15 +2219,23 @@ int nvmx_n2_vmexit_handler(struct cpu_us
>          if ( ctrl & CPU_BASED_ACTIVATE_IO_BITMAP )
>          {
>              unsigned long qual;
> -            u16 port;
> +            u16 port, size;
>  
>              __vmread(EXIT_QUALIFICATION, &qual);
>              port = qual >> 16;
> -            bitmap = nvmx->iobitmap[port >> 15];
> -            if ( bitmap[(port & 0x7fff) >> 3] & (1 << (port & 0x7)) )
> -                nvcpu->nv_vmexit_pending = 1;
> +            size = (qual & 7) + 1;
> +            do {
> +                const u8 *bitmap = nvmx->iobitmap[port >> 15];
> +
> +                if ( bitmap[(port & 0x7fff) >> 3] & (1 << (port & 7)) )
> +                    nvcpu->nv_vmexit_pending = 1;
> +                if ( !--size )
> +                    break;
> +                if ( !++port )
> +                    nvcpu->nv_vmexit_pending = 1;
> +            } while ( !nvcpu->nv_vmexit_pending );
>              if ( !nvcpu->nv_vmexit_pending )
> -               gdprintk(XENLOG_WARNING, "L0 PIO %x.\n", port);
> +                printk(XENLOG_G_WARNING "L0 PIO %04x\n", port);
>          }
>          else if ( ctrl & CPU_BASED_UNCOND_IO_EXITING )
>              nvcpu->nv_vmexit_pending = 1;
> 

Can you use #define's for the bit operations, please?
That makes the code more readable and avoids copy & paste errors.

Christoph


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