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[115.162.127.88]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-32dd7ceecfasm2203933a91.7.2025.09.12.04.33.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 12 Sep 2025 04:33:51 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Itaru Kitayama Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 (1.0) Subject: Re: [PATCH] PMCR_EL0.N is RAZ/WI. At least a build failes in Ubuntu 22.04 LTS. Remove the set function. Date: Fri, 12 Sep 2025 20:33:39 +0900 Message-Id: <3FEB4D87-EEAF-4A21-BCBC-291A4A7C2230@gmail.com> References: <867by4c4v1.wl-maz@kernel.org> Cc: Itaru Kitayama , Oliver Upton , Joey Gouly , K Poulose Suzuki , Zenghui Yu , Paolo Bonzini , Shuah Khan , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Itaru Kitayama In-Reply-To: <867by4c4v1.wl-maz@kernel.org> To: Marc Zyngier X-Mailer: iPhone Mail (22G100) > On Sep 12, 2025, at 20:01, Marc Zyngier wrote: >=20 > =EF=BB=BFOn Fri, 12 Sep 2025 09:27:40 +0100, > Itaru Kitayama wrote: >>=20 >> Signed-off-by: Itaru Kitayama >=20 > This isn't an acceptable commit message. >=20 >> --- >> Seen a build failure with old Ubuntu 22.04 LTS, while the latest release >> has no build issue, a write to the bit fields is RAZ/WI, remove the >> function. >> --- >> tools/testing/selftests/kvm/arm64/vpmu_counter_access.c | 6 ------ >> 1 file changed, 6 deletions(-) >>=20 >> diff --git a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c b/to= ols/testing/selftests/kvm/arm64/vpmu_counter_access.c >> index f16b3b27e32ed7ca57481f27d689d47783aa0345..56214a4430be90b3e1d840f27= 19b22dd44f0b49b 100644 >> --- a/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c >> +++ b/tools/testing/selftests/kvm/arm64/vpmu_counter_access.c >> @@ -45,11 +45,6 @@ static uint64_t get_pmcr_n(uint64_t pmcr) >> return FIELD_GET(ARMV8_PMU_PMCR_N, pmcr); >> } >>=20 >> -static void set_pmcr_n(uint64_t *pmcr, uint64_t pmcr_n) >> -{ >> - u64p_replace_bits((__u64 *) pmcr, pmcr_n, ARMV8_PMU_PMCR_N); >> -} >> - >> static uint64_t get_counters_mask(uint64_t n) >> { >> uint64_t mask =3D BIT(ARMV8_PMU_CYCLE_IDX); >> @@ -490,7 +485,6 @@ static void test_create_vpmu_vm_with_pmcr_n(uint64_t p= mcr_n, bool expect_fail) >> * Setting a larger value of PMCR.N should not modify the field, and >> * return a success. >> */ >> - set_pmcr_n(&pmcr, pmcr_n); >> vcpu_set_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0), pmcr); >> pmcr =3D vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_PMCR_EL0)); >>=20 >>=20 >=20 > So what are you fixing here? A build failure? A semantic defect? > Something else? What makes this a valid change? >=20 > Frankly, I have no idea. >=20 > But KVM definitely allows PMCR_EL0.N to be written from userspace, and > that's not going to change. >=20 Then I=E2=80=99ll drop this patch. Thanks, Itaru. > M. >=20 > -- > Without deviation from the norm, progress is not possible.