Gerd Hoffmann wrote:
> Well, after reading the code a bit more it seems the intention is to
> call the function in a row with others, have stuff queued up (in case
> lazy_mode == PARAVIRT_LAZY_CPU is set) and update everything in one go
> then. I don't think that makes sense for that function as it isn't
> performance-critical. It is called on boot and cpu bringup (well, not
> yet) only, right?
>
Yes, that's right. While its not performance critical in itself, the
idea was that if it were in a stream of other deferred cpu-state
updates, then it should happen in the appropriate order. But in
practice this is mainly to make a context switch a single hypercall, so
the most important ones are stack-switch followed by 3x
update_descriptor (for TLS).
> We have a simliar issue for xen_write_gdt_entry() btw, it calls
> mc_flush() which doesn't work too. I've fixed it that way:
>
> @@ -761,7 +762,13 @@ static asmlinkage void __init xen_start_
> /* set up PDA descriptor */
> pack_descriptor(&low, &high, (unsigned)&boot_pda,
> sizeof(boot_pda)-1,
> 0x80 | DESCTYPE_S | 0x02, 0);
> +#if 0
> xen_write_gdt_entry(cpu_gdt_table, GDT_ENTRY_PDA, low, high);
> +#else
> + if (HYPERVISOR_update_descriptor(virt_to_machine(cpu_gdt_table +
> GDT_ENTRY_PDA).maddr,
> + (u64)high << 32 | low))
> + BUG();
> +#endif
>
> /* set up %gs and init Xen parts of the PDA */
> asm volatile("mov %0, %%gs" : : "r" (__KERNEL_PDA) : "memory");
>
> [ gna, thunderbird isn't great for sending patches inline, you should
> get the idea though ... ]
>
Yeah, that's ugly, but I guess it will do for now.
(You can inline patches without damage in thunderbird if you paste them
as "preformat")
J
