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Thu, 05 Mar 2026 11:59:36 +0000 Date: Thu, 05 Mar 2026 11:59:36 +0000 Message-ID: <86pl5i7ahj.wl-maz@kernel.org> From: Marc Zyngier To: James Clark Cc: Oliver Upton , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Colton Lewis , Alexandru Elisei , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: arm64: Read PMUVer as unsigned In-Reply-To: <20260305-james-kvm-pmuver-sign-v1-1-eea0a2116dd0@linaro.org> References: <20260305-james-kvm-pmuver-sign-v1-1-eea0a2116dd0@linaro.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: james.clark@linaro.org, oupton@kernel.org, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, coltonlewis@google.com, alexandru.elisei@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260305_035940_183406_C3341560 X-CRM114-Status: GOOD ( 23.13 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, 05 Mar 2026 11:50:01 +0000, James Clark wrote: > > ID_AA64DFR0_EL1.PMUVer is an unsigned field, so this skips > initialization of host_data_ptr(nr_event_counters) for PMUv3 for Armv8.8 > onwards as they appear as negative values. > > Fix it by reading it as unsigned. > > Fixes: 2417218f2f23 ("KVM: arm64: Get rid of __kvm_get_mdcr_el2() and related warts") > Signed-off-by: James Clark > --- > arch/arm64/kvm/debug.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c > index 3ad6b7c6e4ba..b8632edba9a3 100644 > --- a/arch/arm64/kvm/debug.c > +++ b/arch/arm64/kvm/debug.c > @@ -76,7 +76,7 @@ void kvm_init_host_debug_data(void) > { > u64 dfr0 = read_sysreg(id_aa64dfr0_el1); > > - if (cpuid_feature_extract_signed_field(dfr0, ID_AA64DFR0_EL1_PMUVer_SHIFT) > 0) > + if (cpuid_feature_extract_unsigned_field(dfr0, ID_AA64DFR0_EL1_PMUVer_SHIFT) > 0) > *host_data_ptr(nr_event_counters) = FIELD_GET(ARMV8_PMU_PMCR_N, > read_sysreg(pmcr_el0)); > How does this work on a system that advertises a non-architected PMU? M. -- Without deviation from the norm, progress is not possible.