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Thu, 18 Jul 2024 03:50:36 +0000 (UTC) From: Shaoqin Huang To: Oliver Upton , Marc Zyngier , kvmarm@lists.linux.dev, Mark Brown Cc: Eric Auger , Sebastian Ott , Cornelia Huck , Shaoqin Huang , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 2/3] KVM: arm64: Allow userspace to change ID_AA64PFR1_EL1 Date: Wed, 17 Jul 2024 23:50:15 -0400 Message-Id: <20240718035017.434996-3-shahuang@redhat.com> In-Reply-To: <20240718035017.434996-1-shahuang@redhat.com> References: <20240718035017.434996-1-shahuang@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240717_205125_780982_BF270613 X-CRM114-Status: GOOD ( 17.18 ) 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 Allow userspace to change the guest-visible value of the register with different way of handling: - Since the RAS and MPAM is not writable in the ID_AA64PFR0_EL1 register, RAS_frac and MPAM_frac are also not writable in the ID_AA64PFR1_EL1 register. - The MTE is controlled by an internal flag (KVM_ARCH_FLAG_MTE_ENABLED), so it's not writable. - For those fields which KVM doesn't know how to handle, they have are not exposed to the guest (being disabled in the register read accessor), those fields value will always be 0. Allow those fields writable is fine, since the userspace can only write 0 into those fields. Maybe in the future KVM know how to handle some of the fields, then they can be written into other value. So let them writable. Those fields include SME, RNDR_trap, NMI, GCS, THE, DF2, PFAR, MTE_frac, MTEX. - The BT, SSBS, CSV2_frac don't introduce any new registers which KVM doesn't know how to handle, they can be written without ill effect. So let them writable. Besides, we don't do the crosscheck in KVM about the CSV2_frac even if it depends on the value of CSV2, it should be made sure by the VMM instead of KVM. Signed-off-by: Shaoqin Huang --- arch/arm64/kvm/sys_regs.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index 4508288b9d38..26b38165a8be 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -2314,7 +2314,10 @@ static const struct sys_reg_desc sys_reg_descs[] = { ID_AA64PFR0_EL1_GIC | ID_AA64PFR0_EL1_AdvSIMD | ID_AA64PFR0_EL1_FP), }, - ID_SANITISED(ID_AA64PFR1_EL1), + ID_WRITABLE(ID_AA64PFR1_EL1, ~(ID_AA64PFR1_EL1_RES0 | + ID_AA64PFR1_EL1_MPAM_frac | + ID_AA64PFR1_EL1_RAS_frac | + ID_AA64PFR1_EL1_MTE)), ID_UNALLOCATED(4,2), ID_UNALLOCATED(4,3), ID_WRITABLE(ID_AA64ZFR0_EL1, ~ID_AA64ZFR0_EL1_RES0),