[PATCH v1 1/3] x86/pvclock: add setter for pvclock_pvti_cpu0_va

[PATCH v1 1/3] x86/pvclock: add setter for pvclock_pvti_cpu0_va

[Joao Martins]

Right now there is only a pvclock_pvti_cpu0_va() which is defined
on kvmclock since:

commit dac16fba6fc5
("x86/vdso: Get pvclock data from the vvar VMA instead of the fixmap")

The only user of this interface was kvm. This commit moves
pvclock_pvti_cpu0_va to pvclock which is a more generic place to have it
and adds the correspondent setter routine for it. This allows other
pvclock-based clocksources to use it, such as Xen.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
Changes since RFC:
 (Comments from Andy Lutomirski)
 * Add WARN_ON(vclock_was_used(VCLOCK_PVCLOCK)) to
 pvclock_set_pvti_cpu0_va
---
 arch/x86/include/asm/pvclock.h | 22 +++++++++++++---------
 arch/x86/kernel/kvmclock.c     |  6 +-----
 arch/x86/kernel/pvclock.c      | 13 +++++++++++++
 3 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 448cfe1..58399e1 100644
--- a/arch/x86/include/asm/pvclock.h
+++ b/arch/x86/include/asm/pvclock.h
@@ -4,15 +4,6 @@
 #include <linux/clocksource.h>
 #include <asm/pvclock-abi.h>
 
-#ifdef CONFIG_KVM_GUEST
-extern struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void);
-#else
-static inline struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
-{
-	return NULL;
-}
-#endif
-
 /* some helper functions for xen and kvm pv clock sources */
 u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
 u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src);
@@ -101,4 +92,17 @@ struct pvclock_vsyscall_time_info {
 
 #define PVTI_SIZE sizeof(struct pvclock_vsyscall_time_info)
 
+#ifdef CONFIG_PARAVIRT_CLOCK
+void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti);
+struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void);
+#else
+static inline void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)
+{
+}
+static inline struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
+{
+	return NULL;
+}
+#endif
+
 #endif /* _ASM_X86_PVCLOCK_H */
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 2a5cafd..9dfbb79 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -45,11 +45,6 @@ early_param("no-kvmclock", parse_no_kvmclock);
 static struct pvclock_vsyscall_time_info *hv_clock;
 static struct pvclock_wall_clock wall_clock;
 
-struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
-{
-	return hv_clock;
-}
-
 /*
  * The wallclock is the time of day when we booted. Since then, some time may
  * have elapsed since the hypervisor wrote the data. So we try to account for
@@ -330,6 +325,7 @@ int __init kvm_setup_vsyscall_timeinfo(void)
 		return 1;
 	}
 
+	pvclock_set_pvti_cpu0_va(hv_clock);
 	put_cpu();
 
 	kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
index 9e93fe5..b281060 100644
--- a/arch/x86/kernel/pvclock.c
+++ b/arch/x86/kernel/pvclock.c
@@ -23,8 +23,10 @@
 #include <linux/bootmem.h>
 #include <asm/fixmap.h>
 #include <asm/pvclock.h>
+#include <asm/vgtod.h>
 
 static u8 valid_flags __read_mostly = 0;
+static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly = NULL;
 
 void pvclock_set_flags(u8 flags)
 {
@@ -142,3 +144,14 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
 
 	set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
 }
+
+void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)
+{
+	WARN_ON(vclock_was_used(VCLOCK_PVCLOCK));
+	pvti_cpu0_va = pvti;
+}
+
+struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
+{
+	return pvti_cpu0_va;
+}
-- 
2.1.4

[PATCH v1 3/3] MAINTAINERS: xen, kvm: track pvclock-abi.h changes

[Joao Martins]

This file defines an ABI shared between guest and hypervisor(s)
(KVM, Xen) and as such there should be an correspondent entry in
MAINTAINERS file. Notice that there's already a text notice at the
top of the header file, hence this commit simply enforces it more
explicitly and have both peers noticed when such changes happen.

Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
This was suggested by folks at xen-devel as we missed some of the
ABI additions (e.g. flags field in pvti, TSC stable bit) - so this
patch is to help preventing that from happening. Alternatively I
could instead add a "PVCLOCK ABI" section in this file with the
two mailing lists.
---
 MAINTAINERS | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 26edd83..c4315d1 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7041,6 +7041,7 @@ F:	Documentation/virtual/kvm/
 F:	arch/*/kvm/
 F:	arch/x86/kernel/kvm.c
 F:	arch/x86/kernel/kvmclock.c
+F:	arch/x86/include/asm/pvclock-abi.h
 F:	arch/*/include/asm/kvm*
 F:	include/linux/kvm*
 F:	include/uapi/linux/kvm*
@@ -13483,6 +13484,7 @@ M:	Juergen Gross <jgross@suse.com>
 L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git
 S:	Supported
+F:	arch/x86/include/asm/pvclock-abi.h
 F:	arch/x86/xen/
 F:	drivers/*/xen-*front.c
 F:	drivers/xen/
-- 
2.1.4

Re: [PATCH v1 1/3] x86/pvclock: add setter for pvclock_pvti_cpu0_va

[Andy Lutomirski]

On Wed, Jan 25, 2017 at 9:33 AM, Joao Martins <joao.m.martins@oracle.com> wrote:
> Right now there is only a pvclock_pvti_cpu0_va() which is defined
> on kvmclock since:
>
> commit dac16fba6fc5
> ("x86/vdso: Get pvclock data from the vvar VMA instead of the fixmap")
>
> The only user of this interface was kvm. This commit moves
> pvclock_pvti_cpu0_va to pvclock which is a more generic place to have it
> and adds the correspondent setter routine for it. This allows other
> pvclock-based clocksources to use it, such as Xen.

With a minor nit:

Acked-by: Andy Lutomirski <luto@kernel.org>

> +#else
> +static inline void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)
> +{
> +}

How about just not providing pvclock_set_pvti_cpu0_va() in this case?
It'll save three lines of code, and, more importantly, it will force
us to notice if we screw up the Kconfig stuff.

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Re: [PATCH v1 3/3] MAINTAINERS: xen, kvm: track pvclock-abi.h changes

[Andy Lutomirski]

On Wed, Jan 25, 2017 at 9:33 AM, Joao Martins <joao.m.martins@oracle.com> wrote:
> This file defines an ABI shared between guest and hypervisor(s)
> (KVM, Xen) and as such there should be an correspondent entry in
> MAINTAINERS file. Notice that there's already a text notice at the
> top of the header file, hence this commit simply enforces it more
> explicitly and have both peers noticed when such changes happen.
>
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
> This was suggested by folks at xen-devel as we missed some of the
> ABI additions (e.g. flags field in pvti, TSC stable bit) - so this
> patch is to help preventing that from happening. Alternatively I
> could instead add a "PVCLOCK ABI" section in this file with the
> two mailing lists.

If you do the latter, please add me as an R:.

--Andy

Re: [PATCH v1 1/3] x86/pvclock: add setter for pvclock_pvti_cpu0_va

[Joao Martins]

On 01/26/2017 05:25 PM, Andy Lutomirski wrote:
> On Wed, Jan 25, 2017 at 9:33 AM, Joao Martins <joao.m.martins@oracle.com> wrote:
>> Right now there is only a pvclock_pvti_cpu0_va() which is defined
>> on kvmclock since:
>>
>> commit dac16fba6fc5
>> ("x86/vdso: Get pvclock data from the vvar VMA instead of the fixmap")
>>
>> The only user of this interface was kvm. This commit moves
>> pvclock_pvti_cpu0_va to pvclock which is a more generic place to have it
>> and adds the correspondent setter routine for it. This allows other
>> pvclock-based clocksources to use it, such as Xen.
> 
> With a minor nit:
> 
> Acked-by: Andy Lutomirski <luto@kernel.org>
> 
>> +#else
>> +static inline void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)
>> +{
>> +}
> 
> How about just not providing pvclock_set_pvti_cpu0_va() in this case?
> It'll save three lines of code, and, more importantly, it will force
> us to notice if we screw up the Kconfig stuff.
Sounds good, will remove this then. Thanks!

Joao

Re: [PATCH v1 3/3] MAINTAINERS: xen, kvm: track pvclock-abi.h changes

[Joao Martins]

On 01/26/2017 05:25 PM, Andy Lutomirski wrote:
> On Wed, Jan 25, 2017 at 9:33 AM, Joao Martins <joao.m.martins@oracle.com> wrote:
>> This file defines an ABI shared between guest and hypervisor(s)
>> (KVM, Xen) and as such there should be an correspondent entry in
>> MAINTAINERS file. Notice that there's already a text notice at the
>> top of the header file, hence this commit simply enforces it more
>> explicitly and have both peers noticed when such changes happen.
>>
>> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
>> ---
>> This was suggested by folks at xen-devel as we missed some of the
>> ABI additions (e.g. flags field in pvti, TSC stable bit) - so this
>> patch is to help preventing that from happening. Alternatively I
>> could instead add a "PVCLOCK ABI" section in this file with the
>> two mailing lists.
> 
> If you do the latter, please add me as an R:.
OK, Thanks.

Since the ABI is used on both hypervisors I'll leave/wait for maintainers to
voice their preference.

Joao

Re: [PATCH v1 3/3] MAINTAINERS: xen, kvm: track pvclock-abi.h changes

[Juergen Gross]

On 25/01/17 18:33, Joao Martins wrote:
> This file defines an ABI shared between guest and hypervisor(s)
> (KVM, Xen) and as such there should be an correspondent entry in
> MAINTAINERS file. Notice that there's already a text notice at the
> top of the header file, hence this commit simply enforces it more
> explicitly and have both peers noticed when such changes happen.
> 
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
> This was suggested by folks at xen-devel as we missed some of the
> ABI additions (e.g. flags field in pvti, TSC stable bit) - so this
> patch is to help preventing that from happening. Alternatively I
> could instead add a "PVCLOCK ABI" section in this file with the
> two mailing lists.

I don't mind either way. In case of an own section: make it more generic
like "PARAVIRT ABIS" as there might be more than PVCLOCK (if not now
maybe in future).

For both variants:

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


Juergen

> ---
>  MAINTAINERS | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 26edd83..c4315d1 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7041,6 +7041,7 @@ F:	Documentation/virtual/kvm/
>  F:	arch/*/kvm/
>  F:	arch/x86/kernel/kvm.c
>  F:	arch/x86/kernel/kvmclock.c
> +F:	arch/x86/include/asm/pvclock-abi.h
>  F:	arch/*/include/asm/kvm*
>  F:	include/linux/kvm*
>  F:	include/uapi/linux/kvm*
> @@ -13483,6 +13484,7 @@ M:	Juergen Gross <jgross@suse.com>
>  L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
>  T:	git git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git
>  S:	Supported
> +F:	arch/x86/include/asm/pvclock-abi.h
>  F:	arch/x86/xen/
>  F:	drivers/*/xen-*front.c
>  F:	drivers/xen/
> 


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