From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by smtp.lore.kernel.org (Postfix) with ESMTP id CEC64C433EF for ; Wed, 15 Dec 2021 12:15:18 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 4DB684B0F5; Wed, 15 Dec 2021 07:15:18 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu 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 uhk0JGcM54+X; Wed, 15 Dec 2021 07:15:16 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id C2B594B103; Wed, 15 Dec 2021 07:15:16 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id A13F84B0F5 for ; Wed, 15 Dec 2021 07:15:15 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu 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 tuFa-NTlVyWY for ; Wed, 15 Dec 2021 07:15:14 -0500 (EST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 106674B0C3 for ; Wed, 15 Dec 2021 07:15:14 -0500 (EST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A40B9D6E; Wed, 15 Dec 2021 04:15:13 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.67.176]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 950413F774; Wed, 15 Dec 2021 04:15:12 -0800 (PST) Date: Wed, 15 Dec 2021 12:15:09 +0000 From: Mark Rutland To: Oliver Upton Subject: Re: [PATCH v4 3/6] KVM: arm64: Allow guest to set the OSLK bit Message-ID: References: <20211214172812.2894560-1-oupton@google.com> <20211214172812.2894560-4-oupton@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211214172812.2894560-4-oupton@google.com> Cc: linux-arm-kernel@lists.infradead.org, Marc Zyngier , Peter Shier , kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Tue, Dec 14, 2021 at 05:28:09PM +0000, Oliver Upton wrote: > Allow writes to OSLAR and forward the OSLK bit to OSLSR. Do nothing with > the value for now. > > Reviewed-by: Reiji Watanabe > Signed-off-by: Oliver Upton > --- > arch/arm64/include/asm/sysreg.h | 9 ++++++++ > arch/arm64/kvm/sys_regs.c | 39 ++++++++++++++++++++++++++------- > 2 files changed, 40 insertions(+), 8 deletions(-) > > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > index 16b3f1a1d468..46f800bda045 100644 > --- a/arch/arm64/include/asm/sysreg.h > +++ b/arch/arm64/include/asm/sysreg.h > @@ -129,7 +129,16 @@ > #define SYS_DBGWCRn_EL1(n) sys_reg(2, 0, 0, n, 7) > #define SYS_MDRAR_EL1 sys_reg(2, 0, 1, 0, 0) > #define SYS_OSLAR_EL1 sys_reg(2, 0, 1, 0, 4) > + > +#define SYS_OSLAR_OSLK BIT(0) > + > #define SYS_OSLSR_EL1 sys_reg(2, 0, 1, 1, 4) > + > +#define SYS_OSLSR_OSLK BIT(1) > + > +#define SYS_OSLSR_OSLM_MASK (BIT(3) | BIT(0)) > +#define SYS_OSLSR_OSLM BIT(3) Since `OSLM` is the field as a whole, I think this should have another level of hierarchy, e.g. #define SYS_OSLSR_OSLM_MASK (BIT(3) | BIT(0)) #define SYS_OSLSR_OSLM_NI 0 #define SYS_OSLSR_OSLM_OSLK BIT(3) [...] > +static bool trap_oslar_el1(struct kvm_vcpu *vcpu, > + struct sys_reg_params *p, > + const struct sys_reg_desc *r) > +{ > + u64 oslsr; > + > + if (!p->is_write) > + return read_from_write_only(vcpu, p, r); > + > + /* Forward the OSLK bit to OSLSR */ > + oslsr = __vcpu_sys_reg(vcpu, OSLSR_EL1) & ~SYS_OSLSR_OSLK; > + if (p->regval & SYS_OSLAR_OSLK) > + oslsr |= SYS_OSLSR_OSLK; > + > + __vcpu_sys_reg(vcpu, OSLSR_EL1) = oslsr; > + return true; > +} Does changing this affect existing userspace? Previosuly it could read OSLAR_EL1 as 0, whereas now that should be rejected. That might be fine, and if so, it would be good to call that out in the commit message. [...] > @@ -309,9 +331,14 @@ static int set_oslsr_el1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd, > if (err) > return err; > > - if (val != rd->val) > + /* > + * The only modifiable bit is the OSLK bit. Refuse the write if > + * userspace attempts to change any other bit in the register. > + */ > + if ((val & ~SYS_OSLSR_OSLK) != SYS_OSLSR_OSLM) > return -EINVAL; How about: if ((val ^ rd->val) & ~SYS_OSLSR_OSLK) return -EINVAL; ... so that we don't need to hard-code the expected value here, and can more easily change it in future? [...] > @@ -1463,8 +1486,8 @@ static const struct sys_reg_desc sys_reg_descs[] = { > DBG_BCR_BVR_WCR_WVR_EL1(15), > > { SYS_DESC(SYS_MDRAR_EL1), trap_raz_wi }, > - { SYS_DESC(SYS_OSLAR_EL1), trap_raz_wi }, > - { SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1, reset_val, OSLSR_EL1, 0x00000008, > + { SYS_DESC(SYS_OSLAR_EL1), trap_oslar_el1 }, > + { SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1, reset_val, OSLSR_EL1, SYS_OSLSR_OSLM, > .set_user = set_oslsr_el1, }, > { SYS_DESC(SYS_OSDLR_EL1), trap_raz_wi }, > { SYS_DESC(SYS_DBGPRCR_EL1), trap_raz_wi }, > @@ -1937,7 +1960,7 @@ static const struct sys_reg_desc cp14_regs[] = { > > DBGBXVR(0), > /* DBGOSLAR */ > - { Op1( 0), CRn( 1), CRm( 0), Op2( 4), trap_raz_wi }, > + { Op1( 0), CRn( 1), CRm( 0), Op2( 4), trap_oslar_el1 }, As above, I have a slight concern that this could adversely affect existing userspace, but I can also believe that's fine. Thanks, Mark. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm