Re: [Xen-devel] [PATCH v7 2/7] xen/x86: populate PVHv2 Dom0 physical memory map

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.02.17 at 15:24, <roger.pau@xxxxxxxxxx> wrote:
> Craft the Dom0 e820 memory map and populate it. Introduce a helper to remove
> memory pages that are shared between Xen and a domain, and use it in order to
> remove low 1MB RAM regions from dom_io in order to assign them to a PVHv2 
> Dom0.
> 
> On hardware lacking support for unrestricted mode also craft the identity page
> tables and the TSS used for virtual 8086 mode.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
albeit ...

> @@ -44,6 +45,16 @@ static long __initdata dom0_min_nrpages;
>  static long __initdata dom0_max_nrpages = LONG_MAX;
>  
>  /*
> + * Have the TSS cover the ISA port range, which makes it
> + * - 104 bytes base structure
> + * - 32 bytes interrupt redirection bitmap
> + * - 128 bytes I/O bitmap
> + * - one trailing byte
> + * or a total of 265 bytes.
> + */
> +#define HVM_VM86_TSS_SIZE 265

... I'm not convinced the same rationale as used in hvmloader
applies here. Namely, the more without legacy devices, there
should be pretty little reason for such a Dom0 to do port I/O
to any (including the ISA) ports from real mode, nor can I see
the usefulness of invoking INT $n instructions without there
being any firmware.

Jan

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