On 08.08.2025 22:23, Andrew Cooper wrote:
> ... disabled by default. There is a lot of work before FRED can be enabled by
> default.
>
> One part of FRED, the LKGS (Load Kernel GS) instruction, is enumerated
> separately but is mandatory as FRED disallows the SWAPGS instruction.
> Therefore, both CPUID bits must be checked.
See my (further) reply to patch 13 - I think FRED simply ought to depend on
LKGS.
> @@ -20,6 +22,9 @@ unsigned int __ro_after_init ler_msr;
> static bool __initdata opt_ler;
> boolean_param("ler", opt_ler);
>
> +int8_t __ro_after_init opt_fred = 0; /* -1 when supported. */
I'm a little puzzled by the comment? DYM "once default-enabled"? Then ...
> @@ -305,6 +310,32 @@ void __init traps_init(void)
> /* Replace early pagefault with real pagefault handler. */
> _update_gate_addr_lower(&bsp_idt[X86_EXC_PF], entry_PF);
>
> + if ( !cpu_has_fred || !cpu_has_lkgs )
> + {
> + if ( opt_fred )
... this won't work anymore once the initializer is changed.
> + printk(XENLOG_WARNING "FRED not available, ignoring\n");
> + opt_fred = false;
Better use 0 here?
> + }
> +
> + if ( opt_fred == -1 )
> + opt_fred = !pv_shim;
Imo it would be better to have the initializer be -1 right away, and comment
out the "!pv_shim" here, until we mean it to be default-enabled.
> + if ( opt_fred )
> + {
> +#ifdef CONFIG_PV32
> + if ( opt_pv32 )
> + {
> + opt_pv32 = 0;
> + printk(XENLOG_INFO "Disabling PV32 due to FRED\n");
> + }
> +#endif
> + printk("Using FRED event delivery\n");
> + }
> + else
> + {
> + printk("Using IDT event delivery\n");
> + }
Could I talk you into omitting the figure braces here? Hmm, or perhaps you
mean to later move code here.
Jan
