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[2003:c9:3f02:d100:4c15:7eb0:f018:dd01]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-57cb72e992dsm6225534a12.48.2024.06.17.03.45.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Jun 2024 03:45:22 -0700 (PDT) Date: Mon, 17 Jun 2024 12:45:21 +0200 (CEST) From: Sebastian Ott To: Oliver Upton cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Marc Zyngier , James Morse , Suzuki K Poulose , Catalin Marinas , Will Deacon , Shaoqin Huang , Eric Auger Subject: Re: [PATCH v4 3/6] KVM: arm64: add emulation for CTR_EL0 register In-Reply-To: Message-ID: <393a1898-504c-c6a6-3c94-4b67b3f4c573@redhat.com> References: <20240603130507.17597-1-sebott@redhat.com> <20240603130507.17597-4-sebott@redhat.com> <0b148e21-1714-f4f7-bc77-2a12b990572d@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed On Fri, 14 Jun 2024, Oliver Upton wrote: > On Fri, Jun 14, 2024 at 05:31:37PM +0200, Sebastian Ott wrote: > > [...] > >> Hm, but in that case we'd use reset_vm_ftr_id_reg() meaning we would have >> to make IDREG() work for this reg. Either by adding special handling to >> that macro or by increasing kvm->arch.id_regs[] a lot - both options don't >> sound very appealing. > > Hiding some of the ugly details behind IDREG() isn't the worst thing, > IMO. The feature ID registers are not laid out contiguously in the > architecture, so it'd make sense that the corresponding KVM code not be > brittle to this. > > The other benefit is we initialize kvm->arch.ctr_el0 exactly once, just > like the other ID registers. I believe there's a quirk with this patch > where an initialization that happens after a KVM_SET_ONE_REG on CTR_EL0 > will clobber the userspace value. > > So, here's where I'm at locally, I'll work it a bit more and try to > densely pack CTR_EL0 into the id_regs array. I also have some (untested) > changes to get CTR_EL0 to show up in the debugfs interface we now have. > > Mind if I post what I have afterwards? Sure go ahead. Thanks, Sebastian > > commit 6bf81bd50dc16309a627863948d49cfeeb00897e > Author: Sebastian Ott > Date: Mon Jun 3 15:05:03 2024 +0200 > > KVM: arm64: Treat CTR_EL0 as a VM feature ID register > > Signed-off-by: Sebastian Ott > Reviewed-by: Shaoqin Huang > Signed-off-by: Oliver Upton > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 212ae77eefaf..e5b8cdd70914 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -327,10 +327,20 @@ struct kvm_arch { > */ > #define IDREG_IDX(id) (((sys_reg_CRm(id) - 1) << 3) | sys_reg_Op2(id)) > #define IDX_IDREG(idx) sys_reg(3, 0, 0, ((idx) >> 3) + 1, (idx) & Op2_mask) > -#define IDREG(kvm, id) ((kvm)->arch.id_regs[IDREG_IDX(id)]) > +#define IDREG(kvm, id) \ > +(*({ \ > + u64 *__reg; \ > + if ((id) == SYS_CTR_EL0) \ > + __reg = &(kvm)->arch.ctr_el0; \ > + else \ > + __reg = &((kvm)->arch.id_regs[IDREG_IDX(id)]); \ > + __reg; \ > +})) > #define KVM_ARM_ID_REG_NUM (IDREG_IDX(sys_reg(3, 0, 0, 7, 7)) + 1) > u64 id_regs[KVM_ARM_ID_REG_NUM]; > > + u64 ctr_el0; > + > /* Masks for VNCR-baked sysregs */ > struct kvm_sysreg_masks *sysreg_masks; > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index dfabf7aec2c7..1ab2cbbc7a76 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1583,6 +1583,9 @@ static bool is_feature_id_reg(u32 encoding) > */ > static inline bool is_vm_ftr_id_reg(u32 id) > { > + if (id == SYS_CTR_EL0) > + return true; > + > return (sys_reg_Op0(id) == 3 && sys_reg_Op1(id) == 0 && > sys_reg_CRn(id) == 0 && sys_reg_CRm(id) >= 1 && > sys_reg_CRm(id) < 8); > @@ -1886,7 +1889,7 @@ static bool access_ctr(struct kvm_vcpu *vcpu, struct sys_reg_params *p, > if (p->is_write) > return write_to_read_only(vcpu, p, r); > > - p->regval = read_sanitised_ftr_reg(SYS_CTR_EL0); > + p->regval = IDREG(vcpu->kvm, SYS_CTR_EL0); > return true; > } > > @@ -2475,7 +2478,10 @@ static const struct sys_reg_desc sys_reg_descs[] = { > { SYS_DESC(SYS_CCSIDR2_EL1), undef_access }, > { SYS_DESC(SYS_SMIDR_EL1), undef_access }, > { SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 }, > - { SYS_DESC(SYS_CTR_EL0), access_ctr }, > + ID_WRITABLE(CTR_EL0, CTR_EL0_DIC_MASK | > + CTR_EL0_IDC_MASK | > + CTR_EL0_DminLine_MASK | > + CTR_EL0_IminLine_MASK), > { SYS_DESC(SYS_SVCR), undef_access }, > > { PMU_SYS_REG(PMCR_EL0), .access = access_pmcr, .reset = reset_pmcr, > @@ -3714,18 +3720,11 @@ FUNCTION_INVARIANT(midr_el1) > FUNCTION_INVARIANT(revidr_el1) > FUNCTION_INVARIANT(aidr_el1) > > -static u64 get_ctr_el0(struct kvm_vcpu *v, const struct sys_reg_desc *r) > -{ > - ((struct sys_reg_desc *)r)->val = read_sanitised_ftr_reg(SYS_CTR_EL0); > - return ((struct sys_reg_desc *)r)->val; > -} > - > /* ->val is filled in by kvm_sys_reg_table_init() */ > static struct sys_reg_desc invariant_sys_regs[] __ro_after_init = { > { SYS_DESC(SYS_MIDR_EL1), NULL, get_midr_el1 }, > { SYS_DESC(SYS_REVIDR_EL1), NULL, get_revidr_el1 }, > { SYS_DESC(SYS_AIDR_EL1), NULL, get_aidr_el1 }, > - { SYS_DESC(SYS_CTR_EL0), NULL, get_ctr_el0 }, > }; > > static int get_invariant_sys_reg(u64 id, u64 __user *uaddr) > > -- > Thanks, > Oliver > >