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[34.76.131.216]) by smtp.gmail.com with ESMTPSA id 4sm2981074wma.0.2021.02.23.04.34.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Feb 2021 04:34:27 -0800 (PST) Date: Tue, 23 Feb 2021 12:34:22 +0000 From: Andrew Scull To: Marc Zyngier Subject: Re: [PATCH 2/2] KVM: arm64: Log source when panicking from nVHE hyp Message-ID: References: <20210223094927.766572-1-ascull@google.com> <20210223094927.766572-3-ascull@google.com> <87czwr10p9.wl-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <87czwr10p9.wl-maz@kernel.org> Cc: kernel-team@android.com, catalin.marinas@arm.com, will@kernel.org, kvmarm@lists.cs.columbia.edu 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, Feb 23, 2021 at 11:29:54AM +0000, Marc Zyngier wrote: > Hi Andrew, > > On Tue, 23 Feb 2021 09:49:27 +0000, > Andrew Scull wrote: > > > > To aid with debugging, add details of the source of a panic. This is > > done by having nVHE hyp exit to nvhe_hyp_panic_handler() rather than > > directly to panic(). The handler will then add the extra details for > > debugging before panicking the kernel. > > > > If the panic was due to a BUG(), look up the metadata to log the file > > and line, if available, otherwise log the kimg address that can be > > looked up in vmlinux. > > > > Signed-off-by: Andrew Scull > > --- > > arch/arm64/include/asm/kvm_mmu.h | 2 ++ > > arch/arm64/kernel/image-vars.h | 3 +- > > arch/arm64/kvm/handle_exit.c | 38 +++++++++++++++++++++++++ > > arch/arm64/kvm/hyp/include/hyp/switch.h | 2 -- > > arch/arm64/kvm/hyp/nvhe/host.S | 18 ++++++------ > > arch/arm64/kvm/hyp/nvhe/psci-relay.c | 2 -- > > 6 files changed, 49 insertions(+), 16 deletions(-) > > > > diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h > > index e52d82aeadca..f07c55f9dd1e 100644 > > --- a/arch/arm64/include/asm/kvm_mmu.h > > +++ b/arch/arm64/include/asm/kvm_mmu.h > > @@ -130,6 +130,8 @@ void kvm_update_va_mask(struct alt_instr *alt, > > __le32 *origptr, __le32 *updptr, int nr_inst); > > void kvm_compute_layout(void); > > > > +#define __hyp_pa(x) ((phys_addr_t)((x)) + hyp_physvirt_offset) > > + > > static __always_inline unsigned long __kern_hyp_va(unsigned long v) > > { > > asm volatile(ALTERNATIVE_CB("and %0, %0, #1\n" > > diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h > > index f676243abac6..cf12b0d6441e 100644 > > --- a/arch/arm64/kernel/image-vars.h > > +++ b/arch/arm64/kernel/image-vars.h > > @@ -71,8 +71,7 @@ KVM_NVHE_ALIAS(kvm_get_kimage_voffset); > > KVM_NVHE_ALIAS(kvm_vgic_global_state); > > > > /* Kernel symbols used to call panic() from nVHE hyp code (via ERET). */ > > -KVM_NVHE_ALIAS(__hyp_panic_string); > > -KVM_NVHE_ALIAS(panic); > > +KVM_NVHE_ALIAS(nvhe_hyp_panic_handler); > > > > /* Vectors installed by hyp-init on reset HVC. */ > > KVM_NVHE_ALIAS(__hyp_stub_vectors); > > diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c > > index cebe39f3b1b6..5e0d9a5152e5 100644 > > --- a/arch/arm64/kvm/handle_exit.c > > +++ b/arch/arm64/kvm/handle_exit.c > > @@ -291,3 +291,41 @@ void handle_exit_early(struct kvm_vcpu *vcpu, int exception_index) > > if (exception_index == ARM_EXCEPTION_EL1_SERROR) > > kvm_handle_guest_serror(vcpu, kvm_vcpu_get_esr(vcpu)); > > } > > + > > +void __noreturn __cold nvhe_hyp_panic_handler(bool hyp, u64 spsr, u64 elr, > > + u64 par, uintptr_t vcpu, > > + u64 far, u64 hpfar, u64 esr) { > > + extern const char __hyp_panic_string[]; > > Is there any reason left to not to make this a symbol at all, but > instead to feed the string to the panic() call below? No, none. I guess it was only a symbol so nVHE hyp could point at it and doesn't matter any more. There doesn't seem to be a good reason for VHE and nVHE to have the same panic string. > > + u64 elr_in_kimg = __phys_to_kimg(__hyp_pa(elr)); > > + > > + if (!hyp) { > > + kvm_err("Invalid host exception to nVHE hyp!\n"); > > Do we need to have hyp as a parameter? Can't we work that out from the > SPSR passed as a parameter? You're right, that should have some useful information already. Didn't occur to me before, I'll play with it. > > + } else if (ESR_ELx_EC(esr) == ESR_ELx_EC_BRK64 && > > + (esr & ESR_ELx_BRK64_ISS_COMMENT_MASK) == BUG_BRK_IMM) { > > + struct bug_entry *bug = find_bug(elr_in_kimg); > > + const char *file = NULL; > > + unsigned line = 0; > > + > > + /* All hyp bugs, including warnings, are treated as fatal. */ > > + if (bug) { > > +#ifdef CONFIG_DEBUG_BUGVERBOSE > > +#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS > > + file = bug->file; > > +#else > > + file = (const char *)bug + bug->file_disp; > > +#endif > > + line = bug->line; > > +#endif > > It looks like you have lifted this from lib/bugs.c. Bingo! > Would it be worth > making it a helper that lives there? Something like > > struct bug_entry *bug_get_entry(unsigned long pc, char **file, > unsigned int *line); > > that hides the #ifdefery and the fund_bug() call away? The > disable_trace_on_warning() call isn't a problem, as we're about to die > anyway. Yeah, that'd make a lot of sense. Please protect me from the wrath of the community when I touch the common code.. > > + } > > + > > + if (file) { > > + kvm_err("nVHE hyp BUG at: %s:%u!\n", file, line); > > + } else { > > + kvm_err("nVHE hyp BUG at: %016llx!\n", elr_in_kimg); > > + } > > + } else { > > + kvm_err("nVHE hyp panic at: %016llx!\n", elr_in_kimg); > > + } > > + > > + panic(__hyp_panic_string, spsr, elr, esr, far, hpfar, par, vcpu); > > +} > > diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h > > index 84473574c2e7..f9e8bb97d199 100644 > > --- a/arch/arm64/kvm/hyp/include/hyp/switch.h > > +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h > > @@ -30,8 +30,6 @@ > > #include > > #include > > > > -extern const char __hyp_panic_string[]; > > - > > extern struct exception_table_entry __start___kvm_ex_table; > > extern struct exception_table_entry __stop___kvm_ex_table; > > > > diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S > > index 3dc5a9f3e575..d9a9dd66b1a2 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/host.S > > +++ b/arch/arm64/kvm/hyp/nvhe/host.S > > @@ -77,21 +77,19 @@ SYM_FUNC_END(__host_enter) > > SYM_FUNC_START(__hyp_do_panic) > > mov x29, x0 > > > > - /* Load the format string into x0 and arguments into x1-7 */ > > - ldr x0, =__hyp_panic_string > > - > > - mov x6, x3 > > - get_vcpu_ptr x7, x3 > > - > > - mrs x3, esr_el2 > > - mrs x4, far_el2 > > - mrs x5, hpfar_el2 > > + /* Load the panic arguments into x0-7 */ > > + cmp x0, xzr > > + cset x0, ne > > + get_vcpu_ptr x4, x5 > > + mrs x5, far_el2 > > + mrs x6, hpfar_el2 > > + mrs x7, esr_el2 > > > > /* Prepare and exit to the host's panic funciton. */ > > mov lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\ > > PSR_MODE_EL1h) > > msr spsr_el2, lr > > - ldr lr, =panic > > + ldr lr, =nvhe_hyp_panic_handler > > msr elr_el2, lr > > > > /* Enter the host, restoring the host context if it was provided. */ > > diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > > index 8e7128cb7667..54b70189229b 100644 > > --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c > > +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c > > @@ -22,8 +22,6 @@ void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt); > > struct kvm_host_psci_config __ro_after_init kvm_host_psci_config; > > s64 __ro_after_init hyp_physvirt_offset; > > > > -#define __hyp_pa(x) ((phys_addr_t)((x)) + hyp_physvirt_offset) > > - > > #define INVALID_CPU_ID UINT_MAX > > > > struct psci_boot_args { > > -- > > 2.30.0.617.g56c4b15f3c-goog > > > > > > Otherwise, I like the idea! > > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm