On Thu, Mar 18, 2021 at 02:33:11PM +0000, Andrew Scull wrote:
> To aid with debugging, add details of the source of a panic from nVHE
> hyp. 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 an address that can be looked up
> in vmlinux. The hyp offset is also logged to allow other hyp VAs to be
> converted, similar to how the kernel offset is logged during a panic.
>
> __hyp_panic_string is now inlined since it no longer needs to be
> referenced as a symbol and the message is free to diverge between VHE
> and nVHE.
>
> The following is an example of the logs generated by a BUG in nVHE hyp.
>
> [ 46.754840] kvm [307]: nVHE hyp BUG at: arch/arm64/kvm/hyp/nvhe/switch.c:242!
> [ 46.755357] kvm [307]: Hyp Offset: 0xfffea6c58e1e0000
> [ 46.755824] Kernel panic - not syncing: HYP panic:
> [ 46.755824] PS:400003c9 PC:0000d93a82c705ac ESR:f2000800
> [ 46.755824] FAR:0000000080080000 HPFAR:0000000000800800 PAR:0000000000000000
> [ 46.755824] VCPU:0000d93a880d0000
> [ 46.756960] CPU: 3 PID: 307 Comm: kvm-vcpu-0 Not tainted 5.12.0-rc3-00005-gc572b99cf65b-dirty #133
> [ 46.757459] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
> [ 46.758366] Call trace:
> [ 46.758601] dump_backtrace+0x0/0x1b0
> [ 46.758856] show_stack+0x18/0x70
> [ 46.759057] dump_stack+0xd0/0x12c
> [ 46.759236] panic+0x16c/0x334
> [ 46.759426] arm64_kernel_unmapped_at_el0+0x0/0x30
> [ 46.759661] kvm_arch_vcpu_ioctl_run+0x134/0x750
> [ 46.759936] kvm_vcpu_ioctl+0x2f0/0x970
> [ 46.760156] __arm64_sys_ioctl+0xa8/0xec
> [ 46.760379] el0_svc_common.constprop.0+0x60/0x120
> [ 46.760627] do_el0_svc+0x24/0x90
> [ 46.760766] el0_svc+0x2c/0x54
> [ 46.760915] el0_sync_handler+0x1a4/0x1b0
> [ 46.761146] el0_sync+0x170/0x180
> [ 46.761889] SMP: stopping secondary CPUs
> [ 46.762786] Kernel Offset: 0x3e1cd2820000 from 0xffff800010000000
> [ 46.763142] PHYS_OFFSET: 0xffffa9f680000000
> [ 46.763359] CPU features: 0x00240022,61806008
> [ 46.763651] Memory Limit: none
Nice!
> [ 46.813867] ---[ end Kernel panic - not syncing: HYP panic:
> [ 46.813867] PS:400003c9 PC:0000d93a82c705ac ESR:f2000800
> [ 46.813867] FAR:0000000080080000 HPFAR:0000000000800800 PAR:0000000000000000
> [ 46.813867] VCPU:0000d93a880d0000 ]---
Why did these last three lines get printed twice?
> Signed-off-by: Andrew Scull <ascull@xxxxxxxxxx>
> ---
> arch/arm64/include/asm/kvm_mmu.h | 2 ++
> arch/arm64/kernel/image-vars.h | 3 +-
> arch/arm64/kvm/handle_exit.c | 45 +++++++++++++++++++++++++
> 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 --
> arch/arm64/kvm/hyp/vhe/switch.c | 4 +--
> 7 files changed, 56 insertions(+), 20 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index 90873851f677..7c17a67d2291 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -121,6 +121,8 @@ void kvm_update_va_mask(struct alt_instr *alt,
> void kvm_compute_layout(void);
> void kvm_apply_hyp_relocations(void);
>
> +#define __hyp_pa(x) (((phys_addr_t)(x)) + hyp_physvirt_offset)
Just a heads up: but Quentin's series moves this same macro, but to a
different header (arch/arm64/kvm/hyp/include/nvhe/memory.h)
> 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 5aa9ed1e9ec6..5ff2b6909387 100644
> --- a/arch/arm64/kernel/image-vars.h
> +++ b/arch/arm64/kernel/image-vars.h
> @@ -70,8 +70,7 @@ 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..6f48336b1d86 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -291,3 +291,48 @@ 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(u64 esr, u64 spsr, u64 elr,
> + u64 par, uintptr_t vcpu,
> + u64 far, u64 hpfar) {
Interesting, I don't think I've seen __cold used in arch/arm64 before. Does
it make any difference to the generated code?
> + u64 elr_in_kimg = __phys_to_kimg(__hyp_pa(elr));
> + u64 hyp_offset = elr_in_kimg - kaslr_offset() - elr;
> + u64 mode = spsr & PSR_MODE_MASK;
> +
> + /*
> + * The nVHE hyp symbols are not included by kallsyms to avoid issues
> + * with aliasing. That means that the symbols cannot be printed with the
> + * "%pS" format specifier, so fall back to the vmlinux address if
> + * there's no better option.
> + */
> + if (mode != PSR_MODE_EL2t && mode != PSR_MODE_EL2h) {
> + kvm_err("Invalid host exception to nVHE hyp!\n");
> + } 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 int line = 0;
> +
> + /* All hyp bugs, including warnings, are treated as fatal. */
> + if (bug)
> + bug_get_file_line(bug, &file, &line);
> +
> + if (file)
> + kvm_err("nVHE hyp BUG at: %s:%u!\n", file, line);
> + else
> + kvm_err("nVHE hyp BUG at: %016llx!\n", elr + hyp_offset);
> + } else {
> + kvm_err("nVHE hyp panic at: %016llx!\n", elr + hyp_offset);
> + }
> +
> + /*
> + * Hyp has panicked and we're going to handle that by panicking the
> + * kernel. The kernel offset will be revealed in the panic so we're
> + * also safe to reveal the hyp offset as a debugging aid for translating
> + * hyp VAs to vmlinux addresses.
> + */
> + kvm_err("Hyp Offset: 0x%llx\n", hyp_offset);
> +
> + panic("HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%016lx\n",
> + spsr, elr, esr, far, hpfar, par, vcpu);
Is %016lx the right conversion specifier for uintptr_t?
> +}
> diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
> index 6c1f51f25eb3..32d0c036c050 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/switch.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
> @@ -30,8 +30,6 @@
> #include <asm/processor.h>
> #include <asm/thread_info.h>
>
> -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 5d94584840cc..2b23400e0fb3 100644
> --- a/arch/arm64/kvm/hyp/nvhe/host.S
> +++ b/arch/arm64/kvm/hyp/nvhe/host.S
> @@ -79,22 +79,18 @@ SYM_FUNC_START(__hyp_do_panic)
> 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
> hyp_kimg_va lr, x6
> msr elr_el2, lr
>
> mov x29, x0
>
> - /* Load the format string into x0 and arguments into x1-7 */
> - ldr x0, =__hyp_panic_string
> - hyp_kimg_va x0, x6
> -
> - /* Load the format arguments into x1-7. */
> - 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 */
> + mrs x0, esr_el2
> + get_vcpu_ptr x4, x5
> + mrs x5, far_el2
> + mrs x6, hpfar_el2
> + mov x7, xzr // Unused argument
Why do you need to clear x7 if it's unused?
Will
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