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SubjectRe: [PATCH v3] xen: get rid of paravirt op adjust_exception_frame
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> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
> index 811e4ddb3f37..a3dcd83187ce 100644
> --- a/arch/x86/xen/enlighten_pv.c
> +++ b/arch/x86/xen/enlighten_pv.c
> @@ -579,6 +579,71 @@ static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
> preempt_enable();
> }
>
> +#ifdef CONFIG_X86_64
> +static struct {
> + void (*orig)(void);
> + void (*xen)(void);
> + bool ist_okay;
> + bool handle;
> +} trap_array[] = {
> + { debug, xen_xendebug, true, true },
> + { int3, xen_xenint3, true, true },
> + { double_fault, xen_double_fault, true, false },

Is it really worth adding 'handle' member to the structure because of a
single special case? We don't expect to ever have another such vector.

(TBH, I think current implementation of cvt_gate_to_trap() is clearer,
even if it is not as general as what is in this patch. I know that Andy
disagrees).

-boris

> +#ifdef CONFIG_X86_MCE
> + { machine_check, xen_machine_check, true, true },
> +#endif
> + { nmi, xen_nmi, true, true },
> + { overflow, xen_overflow, false, true },
> +#ifdef CONFIG_IA32_EMULATION
> + { entry_INT80_compat, xen_entry_INT80_compat, false, true },
> +#endif
> + { page_fault, xen_page_fault, false, true },
> + { divide_error, xen_divide_error, false, true },
> + { bounds, xen_bounds, false, true },
> + { invalid_op, xen_invalid_op, false, true },
> + { device_not_available, xen_device_not_available, false, true },
> + { coprocessor_segment_overrun, xen_coprocessor_segment_overrun,
> + false, true },
> + { invalid_TSS, xen_invalid_TSS, false, true },
> + { segment_not_present, xen_segment_not_present, false, true },
> + { stack_segment, xen_stack_segment, false, true },
> + { general_protection, xen_general_protection, false, true },
> + { spurious_interrupt_bug, xen_spurious_interrupt_bug, false, true },
> + { coprocessor_error, xen_coprocessor_error, false, true },
> + { alignment_check, xen_alignment_check, false, true },
> + { simd_coprocessor_error, xen_simd_coprocessor_error, false, true },
> +#ifdef CONFIG_TRACING
> + { trace_page_fault, xen_trace_page_fault, false, true },
> +#endif
> +};
> +
> +static bool get_trap_addr(unsigned long *addr, unsigned int ist)
> +{
> + unsigned int nr;
> + bool handle = true, ist_okay = false;
> +
> + /*
> + * Replace trap handler addresses by Xen specific ones.
> + * Check for known traps using IST and whitelist them.
> + * The debugger ones are the only ones we care about.
> + * Xen will handle faults like double_fault, * so we should never see
> + * them. Warn if there's an unexpected IST-using fault handler.
> + */
> + for (nr = 0; nr < ARRAY_SIZE(trap_array); nr++)
> + if (*addr == (unsigned long)trap_array[nr].orig) {
> + *addr = (unsigned long)trap_array[nr].xen;
> + ist_okay = trap_array[nr].ist_okay;
> + handle = trap_array[nr].handle;
> + break;
> + }
> +
> + if (WARN_ON(ist != 0 && !ist_okay))
> + handle = false;
> +
> + return handle;
> +}
> +#endif
> +
> static int cvt_gate_to_trap(int vector, const gate_desc *val,
> struct trap_info *info)
> {
> @@ -591,40 +656,8 @@ static int cvt_gate_to_trap(int vector, const gate_desc *val,
>
> addr = gate_offset(*val);
> #ifdef CONFIG_X86_64
> - /*
> - * Look for known traps using IST, and substitute them
> - * appropriately. The debugger ones are the only ones we care
> - * about. Xen will handle faults like double_fault,
> - * so we should never see them. Warn if
> - * there's an unexpected IST-using fault handler.
> - */
> - if (addr == (unsigned long)debug)
> - addr = (unsigned long)xen_debug;
> - else if (addr == (unsigned long)int3)
> - addr = (unsigned long)xen_int3;
> - else if (addr == (unsigned long)stack_segment)
> - addr = (unsigned long)xen_stack_segment;
> - else if (addr == (unsigned long)double_fault) {
> - /* Don't need to handle these */
> + if (!get_trap_addr(&addr, val->ist))
> return 0;
> -#ifdef CONFIG_X86_MCE
> - } else if (addr == (unsigned long)machine_check) {
> - /*
> - * when xen hypervisor inject vMCE to guest,
> - * use native mce handler to handle it
> - */
> - ;
> -#endif
> - } else if (addr == (unsigned long)nmi)
> - /*
> - * Use the native version as well.
> - */
> - ;
> - else {
> - /* Some other trap using IST? */
> - if (WARN_ON(val->ist != 0))
> - return 0;
> - }
> #endif /* CONFIG_X86_64 */
> info->address = addr;
>

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