From: Fuad Tabba <fuad.tabba@linux.dev>
To: kvm@vger.kernel.org
Cc: kvmarm@lists.linux.dev, Will Deacon <will@kernel.org>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Andre Przywara <andre.przywara@arm.com>,
Oliver Upton <oliver.upton@linux.dev>,
Marc Zyngier <maz@kernel.org>, Fuad Tabba <tabba@google.com>
Subject: [PATCH kvmtool 1/5] arm64: Do not abort on register-dump failures
Date: Mon, 31 Aug 2026 20:24:02 +0100 [thread overview]
Message-ID: <20260831192406.1341841-2-fuad.tabba@linux.dev> (raw)
In-Reply-To: <20260831192406.1341841-1-fuad.tabba@linux.dev>
kvm_cpu__show_registers() and kvm_cpu__show_code() read the vCPU's core
registers with KVM_GET_ONE_REG, and die() if the ioctl fails. Both are
diagnostics. They run from the KVM_EXIT_DEBUG case in kvm_cpu__start(),
from the "lkvm debug -d" dump path in handle_sigusr1(), and from the
panic dump in kvm_cpu_thread().
Once a protected vCPU has run, its registers belong to the guest and
KVM_GET_ONE_REG returns -EPERM. Dying on that turns a diagnostic into a
VMM abort.
Report that the register state is unavailable, with the errno, and
return instead of dying.
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
arm64/kvm-cpu.c | 36 ++++++++++++++++++++++++------------
1 file changed, 24 insertions(+), 12 deletions(-)
diff --git a/arm64/kvm-cpu.c b/arm64/kvm-cpu.c
index 3aa7684..c58d61f 100644
--- a/arm64/kvm-cpu.c
+++ b/arm64/kvm-cpu.c
@@ -476,15 +476,19 @@ void kvm_cpu__show_code(struct kvm_cpu *vcpu)
dprintf(debug_fd, "\n*pc:\n");
reg.id = ARM64_CORE_REG(regs.pc);
- if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0)
- die("KVM_GET_ONE_REG failed (show_code @ PC)");
+ if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0) {
+ pr_err("register state unavailable (pc): %s", strerror(errno));
+ return;
+ }
kvm__dump_mem(vcpu->kvm, data, 32, debug_fd);
dprintf(debug_fd, "\n*lr:\n");
reg.id = ARM64_CORE_REG(regs.regs[30]);
- if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0)
- die("KVM_GET_ONE_REG failed (show_code @ LR)");
+ if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0) {
+ pr_err("register state unavailable (lr): %s", strerror(errno));
+ return;
+ }
kvm__dump_mem(vcpu->kvm, data, 32, debug_fd);
}
@@ -499,23 +503,31 @@ void kvm_cpu__show_registers(struct kvm_cpu *vcpu)
dprintf(debug_fd, "\n Registers:\n");
reg.id = ARM64_CORE_REG(regs.pc);
- if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0)
- die("KVM_GET_ONE_REG failed (pc)");
+ if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0) {
+ pr_err("register state unavailable (pc): %s", strerror(errno));
+ return;
+ }
dprintf(debug_fd, " PC: 0x%lx\n", data);
reg.id = ARM64_CORE_REG(regs.pstate);
- if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0)
- die("KVM_GET_ONE_REG failed (pstate)");
+ if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0) {
+ pr_err("register state unavailable (pstate): %s", strerror(errno));
+ return;
+ }
dprintf(debug_fd, " PSTATE: 0x%lx\n", data);
reg.id = ARM64_CORE_REG(sp_el1);
- if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0)
- die("KVM_GET_ONE_REG failed (sp_el1)");
+ if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0) {
+ pr_err("register state unavailable (sp_el1): %s", strerror(errno));
+ return;
+ }
dprintf(debug_fd, " SP_EL1: 0x%lx\n", data);
reg.id = ARM64_CORE_REG(regs.regs[30]);
- if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0)
- die("KVM_GET_ONE_REG failed (lr)");
+ if (ioctl(vcpu->vcpu_fd, KVM_GET_ONE_REG, ®) < 0) {
+ pr_err("register state unavailable (lr): %s", strerror(errno));
+ return;
+ }
dprintf(debug_fd, " LR: 0x%lx\n", data);
}
--
2.39.5
next prev parent reply other threads:[~2026-08-31 19:24 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-31 19:24 [PATCH kvmtool 0/5] Fix diagnostics and capability probes for protected VMs Fuad Tabba
2026-08-31 19:24 ` Fuad Tabba [this message]
2026-08-31 19:24 ` [PATCH kvmtool 2/5] kvm: Bound-check the exit-reason string lookup Fuad Tabba
2026-08-31 19:24 ` [PATCH kvmtool 3/5] kvm: Name every exit reason the UAPI header defines Fuad Tabba
2026-08-31 19:24 ` [PATCH kvmtool 4/5] arm64: Query steal-time support on the VM fd Fuad Tabba
2026-08-31 19:24 ` [PATCH kvmtool 5/5] arm64: Query counter-offset " Fuad Tabba
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