[v3] Support for Intel temperature sensors (DTS)

[PATCH v3 2/3] x86/platform: Expose DTS sensors MSR

Posted by Teddy Astie 3 days, 2 hours ago

Intel provide CPU sensors through "DTS" MSRs. As there MSR are core-specific
(or package-specific), we can't reliably fetch them from Dom0 directly.
Expose these MSR (if supported) through XENPF_resource_op so that it is
accessible through hypercall.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Teddy Astie <teddy.astie@vates.tech>
---
 xen/arch/x86/include/asm/msr-index.h | 3 +++
 xen/arch/x86/platform_hypercall.c    | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/xen/arch/x86/include/asm/msr-index.h b/xen/arch/x86/include/asm/msr-index.h
index df52587c85..b92a278611 100644
--- a/xen/arch/x86/include/asm/msr-index.h
+++ b/xen/arch/x86/include/asm/msr-index.h
@@ -115,6 +115,9 @@
 #define  MCU_OPT_CTRL_GDS_MIT_DIS           (_AC(1, ULL) <<  4)
 #define  MCU_OPT_CTRL_GDS_MIT_LOCK          (_AC(1, ULL) <<  5)
 
+#define MSR_TEMPERATURE_TARGET              0x000001a2
+#define MSR_PACKAGE_THERM_STATUS            0x000001b1
+
 #define MSR_FRED_RSP_SL0                    0x000001cc
 #define MSR_FRED_RSP_SL1                    0x000001cd
 #define MSR_FRED_RSP_SL2                    0x000001ce
diff --git a/xen/arch/x86/platform_hypercall.c b/xen/arch/x86/platform_hypercall.c
index 79bb99e0b6..237340ee42 100644
--- a/xen/arch/x86/platform_hypercall.c
+++ b/xen/arch/x86/platform_hypercall.c
@@ -27,6 +27,7 @@
 #include <asm/current.h>
 #include <public/platform.h>
 #include <acpi/cpufreq/processor_perf.h>
+#include <asm/cpu-policy.h>
 #include <asm/edd.h>
 #include <asm/microcode.h>
 #include <asm/mtrr.h>
@@ -86,6 +87,11 @@ static bool msr_read_allowed(unsigned int msr)
 
     case MSR_MCU_OPT_CTRL:
         return cpu_has_srbds_ctrl;
+    
+    case MSR_IA32_THERM_STATUS:
+    case MSR_TEMPERATURE_TARGET:
+    case MSR_PACKAGE_THERM_STATUS:
+        return raw_cpu_policy.basic.pm.dts;
     }
 
     if ( ppin_msr && msr == ppin_msr )
-- 
2.51.2



--
Teddy Astie | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech

Re: [PATCH v3 2/3] x86/platform: Expose DTS sensors MSR

Posted by Jan Beulich 2 days, 10 hours ago

On 09.12.2025 18:19, Teddy Astie wrote:
> Intel provide CPU sensors through "DTS" MSRs. As there MSR are core-specific

Nit: s/there MSR/these MSRs/ ?

> @@ -86,6 +87,11 @@ static bool msr_read_allowed(unsigned int msr)
>  
>      case MSR_MCU_OPT_CTRL:
>          return cpu_has_srbds_ctrl;
> +    
> +    case MSR_IA32_THERM_STATUS:
> +    case MSR_TEMPERATURE_TARGET:
> +    case MSR_PACKAGE_THERM_STATUS:
> +        return raw_cpu_policy.basic.pm.dts;

I'm pretty sure it was indicated before that the raw policy is likely wrong to
use for anything like this. The host policy wants using instead, or else specific
justification should be provided.

Jan

Re: [PATCH v3 2/3] x86/platform: Expose DTS sensors MSR

Posted by Teddy Astie 2 days, 10 hours ago

Le 10/12/2025 à 09:32, Jan Beulich a écrit :
> On 09.12.2025 18:19, Teddy Astie wrote:
>> Intel provide CPU sensors through "DTS" MSRs. As there MSR are core-specific
> 
> Nit: s/there MSR/these MSRs/ ?
> 

fixed

>> @@ -86,6 +87,11 @@ static bool msr_read_allowed(unsigned int msr)
>>   
>>       case MSR_MCU_OPT_CTRL:
>>           return cpu_has_srbds_ctrl;
>> +
>> +    case MSR_IA32_THERM_STATUS:
>> +    case MSR_TEMPERATURE_TARGET:
>> +    case MSR_PACKAGE_THERM_STATUS:
>> +        return raw_cpu_policy.basic.pm.dts;
> 
> I'm pretty sure it was indicated before that the raw policy is likely wrong to
> use for anything like this. The host policy wants using instead, or else specific
> justification should be provided.
> 

Indeed, host_cpu_policy is intended here.

> Jan



--
Teddy Astie | Vates XCP-ng Developer

XCP-ng & Xen Orchestra - Vates solutions

web: https://vates.tech