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Fri, 04 Sep 2020 11:10:40 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Fri, 04 Sep 2020 11:10:40 +0100 From: Marc Zyngier To: Catalin Marinas Cc: Vincenzo Frascino , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, Will Deacon , Dave P Martin , Szabolcs Nagy , Kevin Brodsky , Andrey Konovalov , Peter Collingbourne , Andrew Morton , Suzuki K Poulose Subject: Re: [PATCH v8 03/28] arm64: mte: CPU feature detection and initial sysreg configuration In-Reply-To: <20200826170826.GC24545@gaia> References: <20200824182758.27267-1-catalin.marinas@arm.com> <20200824182758.27267-4-catalin.marinas@arm.com> <61bba3c1948651a5221b87f2dfa2872f@kernel.org> <20200825105450.GA22233@C02TF0J2HF1T.local> <8ef4b3d5d860346e47f4238bdb0f2a91@kernel.org> <20200826170826.GC24545@gaia> User-Agent: Roundcube Webmail/1.4.8 Message-ID: <220424c4145ac4093c47531e8819a070@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: catalin.marinas@arm.com, vincenzo.frascino@arm.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, will@kernel.org, Dave.Martin@arm.com, szabolcs.nagy@arm.com, kevin.brodsky@arm.com, andreyknvl@google.com, pcc@google.com, akpm@linux-foundation.org, Suzuki.Poulose@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-Rspamd-Queue-Id: 1111F3D668 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2020-08-26 18:08, Catalin Marinas wrote: > On Tue, Aug 25, 2020 at 02:53:47PM +0100, Marc Zyngier wrote: >> On 2020-08-25 11:54, Catalin Marinas wrote: >> > On Tue, Aug 25, 2020 at 09:53:16AM +0100, Marc Zyngier wrote: >> > > On 2020-08-24 19:27, Catalin Marinas wrote: >> > > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c >> > > > index 077293b5115f..59b91f58efec 100644 >> > > > --- a/arch/arm64/kvm/sys_regs.c >> > > > +++ b/arch/arm64/kvm/sys_regs.c >> > > > @@ -1131,6 +1131,8 @@ static u64 read_id_reg(const struct kvm_vcpu >> > > > *vcpu, >> > > > if (!vcpu_has_sve(vcpu)) >> > > > val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT); >> > > > val &= ~(0xfUL << ID_AA64PFR0_AMU_SHIFT); >> > > > + } else if (id == SYS_ID_AA64PFR1_EL1) { >> > > > + val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT); >> > > >> > > Hiding the capability is fine, but where is the handling of trapping >> > > instructions done? They should result in an UNDEF being injected. >> > >> > They are a few new MTE-specific MSR/MRS which are trapped at EL2 but >> > since KVM doesn't understand them yet, shouldn't it already inject >> > undef back at EL1? That would be safer regardless of MTE support. >> >> An UNDEF will be injected, but not without spitting a nastygram in >> the kernel log (look at emulate_sys_reg()). >> >> The best course of action is to have an entry in the sysreg table >> that would explicitly do the handling. > > Something like below. I'll put them in a separate patch, to be reverted > when we get proper MTE support in KVM. > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 59b91f58efec..c7d5d1bae044 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1384,6 +1384,13 @@ static bool access_ccsidr(struct kvm_vcpu > *vcpu, struct sys_reg_params *p, > return true; > } > > +static bool access_mte_regs(struct kvm_vcpu *vcpu, struct > sys_reg_params *p, > + const struct sys_reg_desc *r) > +{ > + kvm_inject_undefined(vcpu); > + return false; > +} > + > /* sys_reg_desc initialiser for known cpufeature ID registers */ > #define ID_SANITISED(name) { \ > SYS_DESC(SYS_##name), \ > @@ -1549,6 +1556,10 @@ static const struct sys_reg_desc sys_reg_descs[] > = { > { SYS_DESC(SYS_SCTLR_EL1), access_vm_reg, reset_val, SCTLR_EL1, > 0x00C50078 }, > { SYS_DESC(SYS_ACTLR_EL1), access_actlr, reset_actlr, ACTLR_EL1 }, > { SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 }, > + > + { SYS_DESC(SYS_RGSR_EL1), access_mte_regs }, > + { SYS_DESC(SYS_GCR_EL1), access_mte_regs }, > + > { SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = > sve_visibility }, > { SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 }, > { SYS_DESC(SYS_TTBR1_EL1), access_vm_reg, reset_unknown, TTBR1_EL1 }, > @@ -1573,6 +1584,9 @@ static const struct sys_reg_desc sys_reg_descs[] > = { > { SYS_DESC(SYS_ERXMISC0_EL1), trap_raz_wi }, > { SYS_DESC(SYS_ERXMISC1_EL1), trap_raz_wi }, > > + { SYS_DESC(SYS_TFSR_EL1), access_mte_regs }, > + { SYS_DESC(SYS_TFSRE0_EL1), access_mte_regs }, > + > { SYS_DESC(SYS_FAR_EL1), access_vm_reg, reset_unknown, FAR_EL1 }, > { SYS_DESC(SYS_PAR_EL1), NULL, reset_unknown, PAR_EL1 }, Yup, looks good. > (still testing, it takes ages to boot a VM inside inside FVP) You aren't allowed to moan about it until you have tried that with NV! ;-) Thanks, M. -- Jazz is not dead. It just smells funny...