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[91.219.240.2]) by smtp.gmail.com with ESMTPSA id m2sm16387178wrq.25.2020.09.15.03.10.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Sep 2020 03:10:06 -0700 (PDT) From: Vitaly Kuznetsov To: Wei Liu , Linux on Hyper-V List Cc: virtualization@lists.linux-foundation.org, Linux Kernel List , Michael Kelley , Vineeth Pillai , Sunil Muthuswamy , Nuno Das Neves , Wei Liu , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Daniel Lezcano , Thomas Gleixner Subject: Re: [PATCH RFC v1 05/18] clocksource/hyperv: use MSR-based access if running as root In-Reply-To: <20200914112802.80611-6-wei.liu@kernel.org> References: <20200914112802.80611-1-wei.liu@kernel.org> <20200914112802.80611-6-wei.liu@kernel.org> Date: Tue, 15 Sep 2020 12:10:04 +0200 Message-ID: <874knzl5ab.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Wei Liu writes: > Signed-off-by: Wei Liu > --- > drivers/clocksource/hyperv_timer.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c > index 09aa44cb8a91..fe96082ce85e 100644 > --- a/drivers/clocksource/hyperv_timer.c > +++ b/drivers/clocksource/hyperv_timer.c > @@ -426,6 +426,9 @@ static bool __init hv_init_tsc_clocksource(void) > if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE)) > return false; > > + if (hv_root_partition) > + return false; > + Out of pure curiosity, TSC page clocksource seems to be available to the root partition (as HV_MSR_REFERENCE_TSC_AVAILABLE is set), why don't we use it? (I understand that with TSC scaling support in modern CPUs even migration is a no-issue and we can use raw TSC but this all seems to be independent from root/non-root partition question). > hv_read_reference_counter = read_hv_clock_tsc; > phys_addr = virt_to_phys(hv_get_tsc_page()); -- Vitaly