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Mon, 23 Nov 2020 17:04:07 +0000 Date: Mon, 23 Nov 2020 17:04:04 +0000 Message-ID: <87h7pg57jv.wl-maz@kernel.org> From: Marc Zyngier To: David Brazdil Subject: Re: [PATCH v2 19/24] kvm: arm64: Intercept host's PSCI_CPU_ON SMCs In-Reply-To: <20201116204318.63987-20-dbrazdil@google.com> References: <20201116204318.63987-1-dbrazdil@google.com> <20201116204318.63987-20-dbrazdil@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: dbrazdil@google.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org, dennis@kernel.org, tj@kernel.org, cl@linux.com, mark.rutland@arm.com, lorenzo.pieralisi@arm.com, qperret@google.com, ascull@google.com, qwandor@google.com, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201123_120411_786436_D60828FD X-CRM114-Status: GOOD ( 40.23 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , kernel-team@android.com, Lorenzo Pieralisi , Andrew Walbran , Suzuki K Poulose , Catalin Marinas , Quentin Perret , linux-kernel@vger.kernel.org, James Morse , linux-arm-kernel@lists.infradead.org, Tejun Heo , Dennis Zhou , Christoph Lameter , Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry , Andrew Scull Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 16 Nov 2020 20:43:13 +0000, David Brazdil wrote: > > Add a handler of the CPU_ON PSCI call from host. When invoked, it looks > up the logical CPU ID corresponding to the provided MPIDR and populates > the state struct of the target CPU with the provided x0, pc. It then > calls CPU_ON itself, with an entry point in hyp that initializes EL2 > state before returning ERET to the provided PC in EL1. > > There is a simple atomic lock around the reset state struct. If it is > already locked, CPU_ON will return PENDING_ON error code. > > Signed-off-by: David Brazdil > --- > arch/arm64/include/asm/kvm_asm.h | 8 ++- > arch/arm64/kvm/arm.c | 1 + > arch/arm64/kvm/hyp/nvhe/psci-relay.c | 104 +++++++++++++++++++++++++++ > 3 files changed, 110 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h > index 109867fb76f6..2e36ba4be748 100644 > --- a/arch/arm64/include/asm/kvm_asm.h > +++ b/arch/arm64/include/asm/kvm_asm.h > @@ -175,9 +175,11 @@ struct kvm_s2_mmu; > DECLARE_KVM_NVHE_SYM(__kvm_hyp_init); > DECLARE_KVM_NVHE_SYM(__kvm_hyp_host_vector); > DECLARE_KVM_HYP_SYM(__kvm_hyp_vector); > -#define __kvm_hyp_init CHOOSE_NVHE_SYM(__kvm_hyp_init) > -#define __kvm_hyp_host_vector CHOOSE_NVHE_SYM(__kvm_hyp_host_vector) > -#define __kvm_hyp_vector CHOOSE_HYP_SYM(__kvm_hyp_vector) > +DECLARE_KVM_NVHE_SYM(__kvm_hyp_psci_cpu_entry); > +#define __kvm_hyp_init CHOOSE_NVHE_SYM(__kvm_hyp_init) > +#define __kvm_hyp_host_vector CHOOSE_NVHE_SYM(__kvm_hyp_host_vector) > +#define __kvm_hyp_vector CHOOSE_HYP_SYM(__kvm_hyp_vector) > +#define __kvm_hyp_psci_cpu_entry CHOOSE_NVHE_SYM(__kvm_hyp_psci_cpu_entry) > > extern unsigned long kvm_arm_hyp_percpu_base[NR_CPUS]; > DECLARE_KVM_NVHE_SYM(__per_cpu_start); > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index 7d2270eeecfb..c76a8e5bd19c 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -1365,6 +1365,7 @@ static void cpu_init_hyp_mode(void) > > params->vector_hyp_va = (unsigned long)kern_hyp_va(kvm_ksym_ref(__kvm_hyp_host_vector)); > params->stack_hyp_va = kern_hyp_va(__this_cpu_read(kvm_arm_hyp_stack_page) + PAGE_SIZE); > + params->entry_hyp_va = (unsigned long)kern_hyp_va(kvm_ksym_ref(__kvm_hyp_psci_cpu_entry)); It feels really odd to use a per-CPU variable to keep track of something that is essentially a constant. Why can't we just have an assembly version of __kimg_hyp_va() and use that to compute the branch target directly in __kvm_hyp_cpu_entry()? __kvm_hyp_host_vector is another one. > params->pgd_pa = kvm_mmu_get_httbr(); > > /* > diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > index 7542de8bd679..2daf52b59846 100644 > --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c > +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > @@ -9,10 +9,15 @@ > #include > #include > #include > +#include > #include > #include > #include > > +#define INVALID_CPU_ID UINT_MAX > + > +extern char __kvm_hyp_cpu_entry[]; > + > /* Config options set by the host. */ > u32 __ro_after_init kvm_host_psci_version = PSCI_VERSION(0, 0); > u32 __ro_after_init kvm_host_psci_function_id[PSCI_FN_MAX]; > @@ -20,6 +25,14 @@ s64 __ro_after_init hyp_physvirt_offset; > > #define __hyp_pa(x) ((phys_addr_t)((x)) + hyp_physvirt_offset) > > +struct kvm_host_psci_state { > + atomic_t pending_on; > + unsigned long pc; > + unsigned long r0; > +}; > + > +static DEFINE_PER_CPU(struct kvm_host_psci_state, kvm_host_psci_state); > + > static u64 get_psci_func_id(struct kvm_cpu_context *host_ctxt) > { > return host_ctxt->regs.regs[0]; > @@ -76,10 +89,99 @@ static __noreturn unsigned long psci_forward_noreturn(struct kvm_cpu_context *ho > hyp_panic(); /* unreachable */ > } > > +static unsigned int find_cpu_id(u64 mpidr) > +{ > + int i; nit: unsigned int? > + > + if (mpidr != INVALID_HWID) { This is a little ugly on the side [(c) FZ], and deserves a comment ("Reject MPIDRs matching the init value of the __cpu_logical_map[] array"?). Also, I personally prefer a construct that reduces the nesting: if (mpidr == INVALID_HWID) return INVALID_CPU_ID; > + for (i = 0; i < NR_CPUS; i++) { > + if (cpu_logical_map(i) == mpidr) > + return i; > + } > + } > + > + return INVALID_CPU_ID; > +} > + > +static bool try_acquire_reset_state(struct kvm_host_psci_state *cpu_state, > + unsigned long pc, unsigned long r0) > +{ > + if (atomic_cmpxchg_acquire(&cpu_state->pending_on, 0, 1) != 0) What guarantees that this cmpxchg is inlined here? Also, having some names for 0 and 1 would be nice. > + return false; > + > + cpu_state->pc = pc; > + cpu_state->r0 = r0; > + wmb(); > + > + return true; > +} > + > +static void release_reset_state(struct kvm_host_psci_state *cpu_state) > +{ > + atomic_set_release(&cpu_state->pending_on, 0); > +} > + > +static int psci_cpu_on(u64 func_id, struct kvm_cpu_context *host_ctxt) > +{ > + u64 mpidr = host_ctxt->regs.regs[1]; > + unsigned long pc = host_ctxt->regs.regs[2]; > + unsigned long r0 = host_ctxt->regs.regs[3]; > + unsigned int cpu_id; > + struct kvm_host_psci_state *cpu_state; > + struct kvm_nvhe_init_params *cpu_params; > + int ret; > + > + /* > + * Find the logical CPU ID for the given MPIDR. The search set is > + * the set of CPUs that were online at the point of KVM initialization. > + * Booting other CPUs is rejected because their cpufeatures were not > + * checked against the finalized capabilities. This could be relaxed > + * by doing the feature checks in hyp. > + */ > + cpu_id = find_cpu_id(mpidr); > + if (cpu_id == INVALID_CPU_ID) > + return PSCI_RET_INVALID_PARAMS; > + > + cpu_state = per_cpu_ptr(&kvm_host_psci_state, cpu_id); > + cpu_params = per_cpu_ptr(&kvm_init_params, cpu_id); > + > + if (!try_acquire_reset_state(cpu_state, pc, r0)) > + return PSCI_RET_ALREADY_ON; > + > + ret = psci_call(func_id, mpidr, > + __hyp_pa(hyp_symbol_addr(__kvm_hyp_cpu_entry)), > + __hyp_pa(cpu_params)); > + > + /* > + * If CPU_ON was successful, the reset state will be released in > + * kvm_host_psci_cpu_entry(). > + */ > + if (ret != PSCI_RET_SUCCESS) > + release_reset_state(cpu_state); > + return ret; > +} > + > +void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt); > + > +asmlinkage void __noreturn __kvm_hyp_psci_cpu_entry(void) > +{ > + struct kvm_host_psci_state *cpu_state = this_cpu_ptr(&kvm_host_psci_state); > + struct kvm_cpu_context *host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt; > + > + host_ctxt->regs.regs[0] = cpu_state->r0; > + write_sysreg_el2(cpu_state->pc, SYS_ELR); > + > + release_reset_state(cpu_state); > + > + __host_enter(host_ctxt); > +} > + > static unsigned long psci_0_1_handler(u64 func_id, struct kvm_cpu_context *host_ctxt) > { > if (func_id == kvm_host_psci_function_id[PSCI_FN_CPU_OFF]) > return psci_forward(host_ctxt); > + else if (func_id == kvm_host_psci_function_id[PSCI_FN_CPU_ON]) > + return psci_cpu_on(func_id, host_ctxt); > else if (func_id == kvm_host_psci_function_id[PSCI_FN_MIGRATE]) > return psci_forward(host_ctxt); > else > @@ -100,6 +202,8 @@ static unsigned long psci_0_2_handler(u64 func_id, struct kvm_cpu_context *host_ > case PSCI_0_2_FN_SYSTEM_RESET: > psci_forward_noreturn(host_ctxt); > unreachable(); > + case PSCI_0_2_FN64_CPU_ON: > + return psci_cpu_on(func_id, host_ctxt); > default: > return PSCI_RET_NOT_SUPPORTED; > } > -- > 2.29.2.299.gdc1121823c-goog > > Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel