Re: [Xen-devel] [PATCH v4 22/31] xen/x86: allow disabling all emulated devices inside of Xen

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 07/08/15 11:17, Roger Pau Monne wrote:
> Only allow enabling or disabling all the emulated devices inside of Xen,
> right now Xen doesn't support enabling specific emulated devices only.
>
> Signed-off-by: Roger Pau Monnà <roger.pau@xxxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
>  xen/arch/x86/domain.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index c508074..432fe43 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -563,7 +563,8 @@ int arch_domain_create(struct domain *d, unsigned int 
> domcr_flags,
>                            XEN_X86_EMU_IOAPIC | XEN_X86_EMU_PIC |
>                            XEN_X86_EMU_PMU | XEN_X86_EMU_VGA |
>                            XEN_X86_EMU_IOMMU);
> -        if ( (config->emulation_flags & emulation_mask) != emulation_mask )
> +        if ( (config->emulation_flags & emulation_mask) != emulation_mask &&
> +             (config->emulation_flags & emulation_mask) != 0 )
>          {
>              printk(XENLOG_G_ERR "d%d: Xen does not allow HVM creation with 
> the "
>                     "current selection of emulators: %#x.\n", d->domain_id,

Thinking about it, it might be better to have a first check against
~emulation_mask (returning -EINVAL for an unknown emulator selection),
and a second check for == mask || == 0 (returning -EOPNOTSUP for an
unsupported combination of valid emulators).

This will have a knockon effect effect on patch 12.

~Andrew

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