* [PATCH] i386/cpu: Expand MAX_FIXED_COUNTERS from 3 to 4 to for Icelake
@ 2020-03-17 5:54 Like Xu
2020-03-26 12:46 ` Like Xu
2020-03-26 18:48 ` Paolo Bonzini
0 siblings, 2 replies; 4+ messages in thread
From: Like Xu @ 2020-03-17 5:54 UTC (permalink / raw)
To: Paolo Bonzini, Richard Henderson, Eduardo Habkost
Cc: qemu-trivial, qemu-devel, Like Xu
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.xu@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
--
2.21.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] i386/cpu: Expand MAX_FIXED_COUNTERS from 3 to 4 to for Icelake
2020-03-17 5:54 [PATCH] i386/cpu: Expand MAX_FIXED_COUNTERS from 3 to 4 to for Icelake Like Xu
@ 2020-03-26 12:46 ` Like Xu
2020-03-26 18:48 ` Paolo Bonzini
1 sibling, 0 replies; 4+ messages in thread
From: Like Xu @ 2020-03-26 12:46 UTC (permalink / raw)
To: Paolo Bonzini, Richard Henderson, Eduardo Habkost
Cc: qemu-trivial, qemu-devel
Anyone to help review this change?
Thanks,
Like Xu
On 2020/3/17 13:54, 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.xu@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
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] i386/cpu: Expand MAX_FIXED_COUNTERS from 3 to 4 to for Icelake
2020-03-17 5:54 [PATCH] i386/cpu: Expand MAX_FIXED_COUNTERS from 3 to 4 to for Icelake Like Xu
2020-03-26 12:46 ` Like Xu
@ 2020-03-26 18:48 ` Paolo Bonzini
2020-03-26 23:56 ` Like Xu
1 sibling, 1 reply; 4+ messages in thread
From: Paolo Bonzini @ 2020-03-26 18:48 UTC (permalink / raw)
To: Like Xu, Richard Henderson, Eduardo Habkost; +Cc: qemu-trivial, qemu-devel
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.xu@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
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] i386/cpu: Expand MAX_FIXED_COUNTERS from 3 to 4 to for Icelake
2020-03-26 18:48 ` Paolo Bonzini
@ 2020-03-26 23:56 ` Like Xu
0 siblings, 0 replies; 4+ messages in thread
From: Like Xu @ 2020-03-26 23:56 UTC (permalink / raw)
To: Paolo Bonzini
Cc: qemu-trivial, qemu-devel, Eduardo Habkost, Richard Henderson
On 2020/3/27 2:48, Paolo Bonzini wrote:
> 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.xu@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.
The new MAX_FIXED_COUNTERS looks good to me and
and let me follow up this live migration issue.
Thanks,
Like Xu
>
> Thanks,
>
> Paolo
>
>
^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-03-17 5:54 [PATCH] i386/cpu: Expand MAX_FIXED_COUNTERS from 3 to 4 to for Icelake Like Xu
2020-03-26 12:46 ` Like Xu
2020-03-26 18:48 ` Paolo Bonzini
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