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Tue, 2 Mar 2021 01:29:10 +0000 From: Michael Kelley To: Daniel Lezcano , Stephen Hemminger , KY Srinivasan , "wei.liu@kernel.org" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "hpa@zytor.com" , "arnd@arndb.de" , "linux-hyperv@vger.kernel.org" CC: "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "linux-arch@vger.kernel.org" Subject: RE: [PATCH v2 07/10] clocksource/drivers/hyper-v: Handle vDSO differences inline Thread-Topic: [PATCH v2 07/10] clocksource/drivers/hyper-v: Handle vDSO differences inline Thread-Index: AQHXDjh1EVCQ9KI360KRzkAsBhzaBqpvDm2AgADWwPA= Date: Tue, 2 Mar 2021 01:29:10 +0000 Message-ID: References: <1614561332-2523-1-git-send-email-mikelley@microsoft.com> <1614561332-2523-8-git-send-email-mikelley@microsoft.com> <42dc252a-b09a-afeb-6792-9b77669c16e9@linaro.org> In-Reply-To: <42dc252a-b09a-afeb-6792-9b77669c16e9@linaro.org> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: msip_labels: MSIP_Label_f42aa342-8706-4288-bd11-ebb85995028c_Enabled=true; 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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: MWHPR21MB1593.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 13f7cb7f-71ba-4da7-beb6-08d8dd1a9475 X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Mar 2021 01:29:10.1878 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: YjvnMU1LxH0lo4asOHGI4yiuiRg0wwqIbnZlCyF8QimuihVjIcQfGSufQE8f1T82OIy40wL4RDwmG1vKG00x+YrpGkcj14regobOckYeKKI= X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB1788 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Daniel Lezcano Sent: Monday, March 1, 202= 1 4:22 AM >=20 > On 01/03/2021 02:15, Michael Kelley wrote: > > While the driver for the Hyper-V Reference TSC and STIMERs is architect= ure > > neutral, vDSO is implemented for x86/x64, but not for ARM64. Current c= ode > > calls into utility functions under arch/x86 (and coming, under arch/arm= 64) > > to handle the difference. > > > > Change this approach to handle the difference inline based on whether > > VDSO_CLOCK_MODE_HVCLOCK is present. The new approach removes code unde= r > > arch/* since the difference is tied more to the specifics of the Linux > > implementation than to the architecture. > > > > No functional change. >=20 > A suggestion below >=20 >=20 > > Signed-off-by: Michael Kelley > > Reviewed-by: Boqun Feng > > --- > > arch/x86/include/asm/mshyperv.h | 4 ---- > > drivers/clocksource/hyperv_timer.c | 10 ++++++++-- > > 2 files changed, 8 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/h= yperv_timer.c > > index c73c127..5e5e08aa 100644 > > --- a/drivers/clocksource/hyperv_timer.c > > +++ b/drivers/clocksource/hyperv_timer.c > > @@ -372,7 +372,9 @@ static void resume_hv_clock_tsc(struct clocksource = *arg) > > > > static int hv_cs_enable(struct clocksource *cs) >=20 > static __maybe_unused int hv_cs_enable(struct clocksource *cs) >=20 > > { > > - hv_enable_vdso_clocksource(); > > +#ifdef VDSO_CLOCKMODE_HVCLOCK > > + vclocks_set_used(VDSO_CLOCKMODE_HVCLOCK); > > +#endif > > return 0; > > } > > > > @@ -385,6 +387,11 @@ static int hv_cs_enable(struct clocksource *cs) > > .suspend=3D suspend_hv_clock_tsc, > > .resume =3D resume_hv_clock_tsc, > > .enable =3D hv_cs_enable, > > +#ifdef VDSO_CLOCKMODE_HVCLOCK > > + .vdso_clock_mode =3D VDSO_CLOCKMODE_HVCLOCK, > > +#else > > + .vdso_clock_mode =3D VDSO_CLOCKMODE_NONE, > > +#endif >=20 > #ifdef VDSO_CLOCKMODE_HVCLOCK > .enable =3D hv_cs_enable, > .vdso_clock_mode =3D VDSO_CLOCKMODE_HVCLOCK, > #else > .vdso_clock_mode =3D VDSO_CLOCKMODE_NONE, > #endif >=20 Is there any particular benefit (that I might not be recognizing) to having the .enable function be NULL vs. a function that does nothing? I can see the handful of places where the .enable function is invoked, and there doesn't seem to be much difference. In any case, I have no problem with making the change in a v3 of the patch set. Michael