On Thu, May 09, 2019 at 06:47:57PM +0800, Yi Wang wrote:
> There are many functions invoke apic_debug(), which is defined
> a null function by default, and that's incovenient for debuging
> lapic.
>
> This patch allows setting apic debug according to add a apic_dbg
> parameter of kvm.
>
> Signed-off-by: Yi Wang <wang.yi59@xxxxxxxxxx>
> ---
> v2: change apic_dbg to bool and tag __read_mostly. Thanks to Sean.
>
> arch/x86/kvm/lapic.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 9bf70cf..0827e7c 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -54,8 +54,13 @@
> #define PRIu64 "u"
> #define PRIo64 "o"
>
> +static bool apic_dbg __read_mostly;
> +module_param(apic_dbg, bool, 0644);
Probably don't need to shorten "debug".
> +
> /* #define apic_debug(fmt,arg...) printk(KERN_WARNING fmt,##arg) */
> -#define apic_debug(fmt, arg...) do {} while (0)
> +#define apic_debug(fmt, arg...) do { if (apic_dbg) \
> + printk(KERN_DEBUG fmt, ##arg); \
> +} while (0)
Pulling in your comment regarding sched_debug and noirqdebug...
On Thu, May 09, 2019 at 08:29:38AM +0800, wang.yi59@xxxxxxxxxx wrote:
> Also, we have some similar parameters already, such like sched_debug,
> noirqdebug :)
The IRQ debug hook is a completely different beast than the APIC debug
messages.
sched_debug is a much better comparison. The param only exists if
CONFIG_SCHED_DEBUG=y, which is "default y" but "depends on DEBUG_KERNEL".
That seems like the route to go if we want the ability to toggle APIC
debugging at runtime. And if we go with an all encompassing config,
e.g. CONFIG_KVM_DEBUG, we can use it to wrap x86/mmu.c's debug param as
well (and rename it to mmu_debug).
>
> /* 14 is the version for Xeon and Pentium 8.4.8*/
> #define APIC_VERSION (0x14UL | ((KVM_APIC_LVT_NUM - 1) << 16))
> --
> 1.8.3.1
>
