From: Oliver Upton <oupton@google.com>
To: Reiji Watanabe <reijiw@google.com>
Cc: Marc Zyngier <maz@kernel.org>,
kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Will Deacon <will@kernel.org>, Andrew Jones <drjones@redhat.com>,
Fuad Tabba <tabba@google.com>,
Peng Liang <liangpeng10@huawei.com>,
Peter Shier <pshier@google.com>,
Ricardo Koller <ricarkol@google.com>,
Jing Zhang <jingzhangos@google.com>,
Raghavendra Rao Anata <rananta@google.com>
Subject: Re: [PATCH v5 10/27] KVM: arm64: Hide IMPLEMENTATION DEFINED PMU support for the guest
Date: Tue, 15 Feb 2022 18:57:47 +0000 [thread overview]
Message-ID: <Ygv3q/+arejIWnzs@google.com> (raw)
In-Reply-To: <20220214065746.1230608-11-reijiw@google.com>
Hi Reiji,
On Sun, Feb 13, 2022 at 10:57:29PM -0800, Reiji Watanabe wrote:
> When ID_AA64DFR0_EL1.PMUVER or ID_DFR0_EL1.PERFMON is 0xf, which
> means IMPLEMENTATION DEFINED PMU supported, KVM unconditionally
> expose the value for the guest as it is. Since KVM doesn't support
> IMPLEMENTATION DEFINED PMU for the guest, in that case KVM should
> expose 0x0 (PMU is not implemented) instead.
>
> Change cpuid_feature_cap_perfmon_field() to update the field value
> to 0x0 when it is 0xf.
Definitely agree with the change in this patch. Do we need to tolerate
writes of 0xf for ABI compatibility (even if it is nonsensical)?
Otherwise a guest with IMP_DEF PMU cannot be migrated to a newer kernel.
--
Thanks,
Oliver
next prev parent reply other threads:[~2022-02-15 18:57 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-14 6:57 [PATCH v5 00/27] KVM: arm64: Make CPU ID registers writable by userspace Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 01/27] KVM: arm64: Introduce a validation function for an ID register Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 02/27] KVM: arm64: Save ID registers' sanitized value per guest Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 03/27] KVM: arm64: Introduce struct id_reg_info Reiji Watanabe
2022-02-17 5:14 ` Oliver Upton
2022-02-22 6:12 ` Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 04/27] KVM: arm64: Make ID_AA64PFR0_EL1 writable Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 05/27] KVM: arm64: Make ID_AA64PFR1_EL1 writable Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 06/27] KVM: arm64: Make ID_AA64ISAR0_EL1 writable Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 07/27] KVM: arm64: Make ID_AA64ISAR1_EL1 writable Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 08/27] KVM: arm64: Make ID_AA64MMFR0_EL1 writable Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 09/27] KVM: arm64: Make ID_AA64MMFR1_EL1 writable Reiji Watanabe
2022-02-15 18:53 ` Oliver Upton
2022-02-15 20:24 ` Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 10/27] KVM: arm64: Hide IMPLEMENTATION DEFINED PMU support for the guest Reiji Watanabe
2022-02-15 18:57 ` Oliver Upton [this message]
2022-02-16 2:52 ` Reiji Watanabe
2022-02-17 4:59 ` Oliver Upton
2022-02-14 6:57 ` [PATCH v5 11/27] KVM: arm64: Make ID_AA64DFR0_EL1 writable Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 12/27] KVM: arm64: Make ID_DFR0_EL1 writable Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 13/27] KVM: arm64: Make MVFR1_EL1 writable Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 14/27] KVM: arm64: Make ID registers without id_reg_info writable Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 15/27] KVM: arm64: Add consistency checking for frac fields of ID registers Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 16/27] KVM: arm64: Introduce KVM_CAP_ARM_ID_REG_CONFIGURABLE capability Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 17/27] KVM: arm64: Add kunit test for ID register validation Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 18/27] KVM: arm64: Use vcpu->arch cptr_el2 to track value of cptr_el2 for VHE Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 19/27] KVM: arm64: Use vcpu->arch.mdcr_el2 to track value of mdcr_el2 Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 20/27] KVM: arm64: Introduce framework to trap disabled features Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 21/27] KVM: arm64: Trap disabled features of ID_AA64PFR0_EL1 Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 22/27] KVM: arm64: Trap disabled features of ID_AA64PFR1_EL1 Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 23/27] KVM: arm64: Trap disabled features of ID_AA64DFR0_EL1 Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 24/27] KVM: arm64: Trap disabled features of ID_AA64MMFR1_EL1 Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 25/27] KVM: arm64: Trap disabled features of ID_AA64ISAR1_EL1 Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 26/27] KVM: arm64: Add kunit test for trap initialization Reiji Watanabe
2022-02-14 6:57 ` [PATCH v5 27/27] KVM: arm64: selftests: Introduce id_reg_test Reiji Watanabe
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