[PATCH linux-next v2 0/2] x86/xen TSC related cleanups

[PATCH linux-next v2 0/2] x86/xen TSC related cleanups

[Krister Johansen]

Hi,
Enclosed please find a pair of patches that perform some additional cleanup
that was suggested by Boris, Jan and Thomas.

Specifically: this resync's arch/x86/include/asm/xen/cpuid.h from its
upstream source in the Xen tree, and then uses one of the new #define-s to
replace a constant in x86/xen/time.c that was previously only numerically
defined.  Pedantic code from v1 is dropped in favor of a more appropriate
return statement.

Changes from v1:

- Coding style fixup in arch/x86/xen/time.c (Feedback from Thomas Gleixner)


Krister Johansen (2):
  xen: update arch/x86/include/asm/xen/cpuid.h
  x86/xen/time: cleanup xen_tsc_safe_clocksource

 arch/x86/include/asm/xen/cpuid.h | 22 ++++++++++++++++++----
 arch/x86/xen/time.c              |  7 ++-----
 2 files changed, 20 insertions(+), 9 deletions(-)

-- 
2.25.1

[PATCH linux-next v2 1/2] xen: update arch/x86/include/asm/xen/cpuid.h

[Krister Johansen]

Update arch/x86/include/asm/xen/cpuid.h from the Xen tree to get newest
definitions.  This picks up some TSC mode definitions and comment
formatting changes.

Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
---
 arch/x86/include/asm/xen/cpuid.h | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/xen/cpuid.h b/arch/x86/include/asm/xen/cpuid.h
index 6daa9b0c8d11..a3c29b1496c8 100644
--- a/arch/x86/include/asm/xen/cpuid.h
+++ b/arch/x86/include/asm/xen/cpuid.h
@@ -89,11 +89,21 @@
  * Sub-leaf 2: EAX: host tsc frequency in kHz
  */
 
+#define XEN_CPUID_TSC_EMULATED               (1u << 0)
+#define XEN_CPUID_HOST_TSC_RELIABLE          (1u << 1)
+#define XEN_CPUID_RDTSCP_INSTR_AVAIL         (1u << 2)
+
+#define XEN_CPUID_TSC_MODE_DEFAULT           (0)
+#define XEN_CPUID_TSC_MODE_ALWAYS_EMULATE    (1u)
+#define XEN_CPUID_TSC_MODE_NEVER_EMULATE     (2u)
+#define XEN_CPUID_TSC_MODE_PVRDTSCP          (3u)
+
 /*
  * Leaf 5 (0x40000x04)
  * HVM-specific features
  * Sub-leaf 0: EAX: Features
  * Sub-leaf 0: EBX: vcpu id (iff EAX has XEN_HVM_CPUID_VCPU_ID_PRESENT flag)
+ * Sub-leaf 0: ECX: domain id (iff EAX has XEN_HVM_CPUID_DOMID_PRESENT flag)
  */
 #define XEN_HVM_CPUID_APIC_ACCESS_VIRT (1u << 0) /* Virtualized APIC registers */
 #define XEN_HVM_CPUID_X2APIC_VIRT      (1u << 1) /* Virtualized x2APIC accesses */
@@ -102,12 +112,16 @@
 #define XEN_HVM_CPUID_VCPU_ID_PRESENT  (1u << 3) /* vcpu id is present in EBX */
 #define XEN_HVM_CPUID_DOMID_PRESENT    (1u << 4) /* domid is present in ECX */
 /*
- * Bits 55:49 from the IO-APIC RTE and bits 11:5 from the MSI address can be
- * used to store high bits for the Destination ID. This expands the Destination
- * ID field from 8 to 15 bits, allowing to target APIC IDs up 32768.
+ * With interrupt format set to 0 (non-remappable) bits 55:49 from the
+ * IO-APIC RTE and bits 11:5 from the MSI address can be used to store
+ * high bits for the Destination ID. This expands the Destination ID
+ * field from 8 to 15 bits, allowing to target APIC IDs up 32768.
  */
 #define XEN_HVM_CPUID_EXT_DEST_ID      (1u << 5)
-/* Per-vCPU event channel upcalls */
+/*
+ * Per-vCPU event channel upcalls work correctly with physical IRQs
+ * bound to event channels.
+ */
 #define XEN_HVM_CPUID_UPCALL_VECTOR    (1u << 6)
 
 /*
-- 
2.25.1

[PATCH linux-next v2 2/2] x86/xen/time: cleanup xen_tsc_safe_clocksource

[Krister Johansen]

Modifies xen_tsc_safe_clocksource() to use newly defined constants from
arch/x86/include/asm/xen/cpuid.h.  This replaces a numeric value with
XEN_CPUID_TSC_MODE_NEVER_EMULATE, and deletes a comment that is now self
explanatory.

There should be no change in the function's behavior.

Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
---
 arch/x86/xen/time.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 95140609c8a8..94056013a2a4 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -20,6 +20,7 @@
 #include <asm/pvclock.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
+#include <asm/xen/cpuid.h>
 
 #include <xen/events.h>
 #include <xen/features.h>
@@ -495,11 +496,7 @@ static int __init xen_tsc_safe_clocksource(void)
 	/* Leaf 4, sub-leaf 0 (0x40000x03) */
 	cpuid_count(xen_cpuid_base() + 3, 0, &eax, &ebx, &ecx, &edx);
 
-	/* tsc_mode = no_emulate (2) */
-	if (ebx != 2)
-		return 0;
-
-	return 1;
+	return ebx == XEN_CPUID_TSC_MODE_NEVER_EMULATE;
 }
 
 static void __init xen_time_init(void)
-- 
2.25.1

Re: [PATCH linux-next v2 0/2] x86/xen TSC related cleanups

[Juergen Gross]

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On 22.02.23 18:54, Krister Johansen wrote:
> Hi,
> Enclosed please find a pair of patches that perform some additional cleanup
> that was suggested by Boris, Jan and Thomas.
> 
> Specifically: this resync's arch/x86/include/asm/xen/cpuid.h from its
> upstream source in the Xen tree, and then uses one of the new #define-s to
> replace a constant in x86/xen/time.c that was previously only numerically
> defined.  Pedantic code from v1 is dropped in favor of a more appropriate
> return statement.
> 
> Changes from v1:
> 
> - Coding style fixup in arch/x86/xen/time.c (Feedback from Thomas Gleixner)
> 
> 
> Krister Johansen (2):
>    xen: update arch/x86/include/asm/xen/cpuid.h
>    x86/xen/time: cleanup xen_tsc_safe_clocksource
> 
>   arch/x86/include/asm/xen/cpuid.h | 22 ++++++++++++++++++----
>   arch/x86/xen/time.c              |  7 ++-----
>   2 files changed, 20 insertions(+), 9 deletions(-)
> 

For both patches:

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

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