On 17/03/20 06:54, Like Xu wrote:
> In the Intel SDM, "Table 18-2. Association of Fixed-Function
> Performance Counters with Architectural Performance Events",
> we may have a new fixed counter 'TOPDOWN.SLOTS' (since Icelake),
> which counts the number of available slots for an unhalted
> logical processor. Check commit 6017608936 in the kernel tree.
>
> Signed-off-by: Like Xu <like...@linux.intel.com>
> ---
> target/i386/cpu.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index 576f309bbf..ec2b67d425 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -1185,7 +1185,7 @@ typedef struct {
> #define CPU_NB_REGS CPU_NB_REGS32
> #endif
>
> -#define MAX_FIXED_COUNTERS 3
> +#define MAX_FIXED_COUNTERS 4
> #define MAX_GP_COUNTERS (MSR_IA32_PERF_STATUS - MSR_P6_EVNTSEL0)
>
> #define TARGET_INSN_START_EXTRA_WORDS 1
>
Hi Like, the problem with this patch is that it breaks live migration;
the vmstate_msr_architectural_pmu record hardcodes MAX_FIXED_COUNTERS as
the number of registers.
So it's more complicated, you need to add a new subsection (following
vmstate_msr_architectural_pmu) and transmit it only if the 4th counter
is nonzero (instead of the more complicated check in pmu_enable_needed).
Just to be safe, I'd make the new subsection hold 16 counters and bump
MAX_FIXED_COUNTERS to 16.
Thanks,
Paolo
