From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Martin Subject: [RFC PATCH v2 10/23] KVM: arm64: Extend reset_unknown() to handle mixed RES0/UNKNOWN registers Date: Fri, 28 Sep 2018 14:39:14 +0100 Message-ID: <1538141967-15375-11-git-send-email-Dave.Martin@arm.com> References: <1538141967-15375-1-git-send-email-Dave.Martin@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 7C5A64A1E5 for ; Fri, 28 Sep 2018 09:40:36 -0400 (EDT) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xj63rqPmPTph for ; Fri, 28 Sep 2018 09:40:35 -0400 (EDT) Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 719E14A21E for ; Fri, 28 Sep 2018 09:40:35 -0400 (EDT) In-Reply-To: <1538141967-15375-1-git-send-email-Dave.Martin@arm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: kvmarm@lists.cs.columbia.edu Cc: Okamoto Takayuki , Christoffer Dall , Ard Biesheuvel , Marc Zyngier , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org List-Id: kvmarm@lists.cs.columbia.edu The reset_unknown() system register helper initialises a guest register to a distinctive junk value on vcpu reset, to help expose and debug deficient register initialisation within the guest. Some registers such as the SVE control register ZCR_EL1 contain a mixture of UNKNOWN fields and RES0 bits. For these, reset_unknown() does not work at present, since it sets all bits to junk values instead of just the wanted bits. There is no need to craft another special helper just for that, since reset_unknown() almost does the appropriate thing anyway. This patch takes advantage of the ununused val field in struct sys_reg_desc to specify a mask of bits that should be initialised to zero instead of junk. All existing users of reset_unknown() do not (and should not) define a value for val, so they will implicitly set it to zero, resulting in all bits being made UNKNOWN by this function: thus, this patch makes no functional change for currently defined registers. Future patches will make use of non-zero val. Signed-off-by: Dave Martin --- arch/arm64/kvm/sys_regs.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/sys_regs.h b/arch/arm64/kvm/sys_regs.h index cd710f8..24bac06 100644 --- a/arch/arm64/kvm/sys_regs.h +++ b/arch/arm64/kvm/sys_regs.h @@ -89,7 +89,9 @@ static inline void reset_unknown(struct kvm_vcpu *vcpu, { BUG_ON(!r->reg); BUG_ON(r->reg >= NR_SYS_REGS); - __vcpu_sys_reg(vcpu, r->reg) = 0x1de7ec7edbadc0deULL; + + /* If non-zero, r->val specifies which register bits are RES0: */ + __vcpu_sys_reg(vcpu, r->reg) = 0x1de7ec7edbadc0deULL & ~r->val; } static inline void reset_val(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) -- 2.1.4