>>> On 10.04.18 at 09:58, <jgr...@suse.com> wrote:
> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -1955,14 +1955,29 @@ clustered mode. The default, given no hint from the
> **FADT**, is cluster
> mode.
>
> ### xpti
> -> `= <boolean>`
> +> `= List of [ default | <boolean> | dom0=<bool> | domu=<bool> ]`
>
> -> Default: `false` on AMD hardware
> +> Default: `false` on hardware not vulnerable to Meltdown (e.g. AMD)
> > Default: `true` everywhere else
>
> Override default selection of whether to isolate 64-bit PV guest page
> tables.
>
> +`true` activates page table isolation even on hardware not vulnerable by
> +Meltdown for all domains.
> +
> +`false` deactivates page table isolation on all systems for all domains.
> +
> +`default` sets the default behaviour.
> +
> +`dom0=false` deactivates page table isolation for dom0.
> +
> +`dom0=true` activates page table isolation for dom0.
> +
> +`domu=false` deactivates page table isolation for guest domains.
> +
> +`domu=true` activates page table isolation for guest domains.
This is too verbose / repetitive for my taste.
> @@ -205,6 +208,10 @@ int pv_domain_initialise(struct domain *d)
> /* 64-bit PV guest by default. */
> d->arch.is_32bit_pv = d->arch.has_32bit_shinfo = 0;
>
> + d->arch.pv_domain.xpti = (d->domain_id == hardware_domid)
> + ? (opt_xpti & XPTI_DOM0)
> + : (opt_xpti & XPTI_DOMU);
I would generally prefer to have as little redundancy as possible in
such expressions, i.e.
d->arch.pv_domain.xpti = opt_xpti & (d->domain_id == hardware_domid
? XPTI_DOM0 : XPTI_DOMU);
Furthermore - shouldn't this cover domain 0 as well as the hardware
domain, even if - in case they are different - domain 0 should be
short lived?
> --- a/xen/arch/x86/spec_ctrl.c
> +++ b/xen/arch/x86/spec_ctrl.c
> @@ -193,6 +193,68 @@ static bool __init retpoline_safe(void)
> }
> }
>
> +#define XPTI_DEFAULT 0xff
> +uint8_t opt_xpti = XPTI_DEFAULT;
__read_mostly
> --- a/xen/include/asm-x86/spec_ctrl.h
> +++ b/xen/include/asm-x86/spec_ctrl.h
> @@ -29,6 +29,10 @@ void init_speculation_mitigations(void);
> extern bool opt_ibpb;
> extern uint8_t default_bti_ist_info;
>
> +extern uint8_t opt_xpti;
> +#define XPTI_DOM0 0x01
> +#define XPTI_DOMU 0x02
OPT_XPTI_DOM{0,U} would perhaps have been better.
Anyway, in the interest of getting done with this
Reviewed-by: Jan Beulich <jbeul...@suse.com>
with or without some or all of the suggestions addressed.
Jan
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