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Fri, 10 Jul 2026 06:25:21 -0700 (PDT) Message-ID: <4beddbefdc81aa8ac48ee9d73d03c3f023eab93a.camel@gmail.com> Subject: Re: [patch 17/48] x86/apic: Avoid the PVOPS indirection for the TSC deadline timer From: Artem Bityutskiy To: Thomas Gleixner , LKML Cc: Anna-Maria Behnsen , John Stultz , Stephen Boyd , Daniel Lezcano , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , x86@kernel.org, Peter Zijlstra , Frederic Weisbecker , Eric Dumazet Date: Fri, 10 Jul 2026 16:25:18 +0300 In-Reply-To: <20260224163429.877429827@kernel.org> References: <20260224163022.795809588@kernel.org> <20260224163429.877429827@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2026-02-24 at 17:36 +0100, Thomas Gleixner wrote: > XEN PV does not emulate the TSC deadline timer, so the PVOPS indirection > for writing the deadline MSR can be avoided completely. >=20 > Use native_wrmsrq() instead. >=20 > Signed-off-by: Thomas Gleixner > --- > arch/x86/kernel/apic/apic.c | 13 ++++++++++--- > 1 file changed, 10 insertions(+), 3 deletions(-) >=20 > --- a/arch/x86/kernel/apic/apic.c > +++ b/arch/x86/kernel/apic/apic.c > @@ -426,7 +426,7 @@ static int lapic_next_deadline(unsigned > */ > u64 tsc =3D rdtsc(); > =20 > - wrmsrq(MSR_IA32_TSC_DEADLINE, tsc + (((u64) delta) * TSC_DIVISOR)); > + native_wrmsrq(MSR_IA32_TSC_DEADLINE, tsc + (((u64) delta) * TSC_DIVISOR= )); > return 0; > } > =20 > @@ -450,7 +450,7 @@ static int lapic_timer_shutdown(struct c > * the timer _and_ zero the counter registers: > */ > if (v & APIC_LVT_TIMER_TSCDEADLINE) > - wrmsrq(MSR_IA32_TSC_DEADLINE, 0); > + native_wrmsrq(MSR_IA32_TSC_DEADLINE, 0); Hi Thomas, unfortunately for me and anyone who wants to trace MSR_IA32_TSC_DEADLINE: - wrmsrq() did trigger the 'write_msr' trace event. - native_wrmsrq() does not trigger it. I am not sure what is the best way to add the tracepoint back, but before I even try, I wanted to ask if you would be OK with that. Thank you!