From: Reiji Watanabe <reijiw@google.com>
To: Marc Zyngier <maz@kernel.org>, kvmarm@lists.cs.columbia.edu
Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Ricardo Koller <ricarkol@google.com>,
Oliver Upton <oliver.upton@linux.dev>,
Jing Zhang <jingzhangos@google.com>,
Raghavendra Rao Anata <rananta@google.com>,
Reiji Watanabe <reijiw@google.com>
Subject: [PATCH 1/3] KVM: arm64: Don't set PSTATE.SS when Software Step state is Active-pending
Date: Thu, 8 Sep 2022 21:46:34 -0700 [thread overview]
Message-ID: <20220909044636.1997755-2-reijiw@google.com> (raw)
In-Reply-To: <20220909044636.1997755-1-reijiw@google.com>
Currently, PSTATE.SS is set on every guest entry if single-step is
enabled for the vCPU by userspace. However, it could cause extra
single-step execution without returning to userspace, which shouldn't
be performed, if the Software Step state at the last guest exit was
Active-pending (i.e. the last exit was not triggered by Software Step
exception, but by an asynchronous exception after the single-step
execution is performed).
Fix this by not setting PSTATE.SS on guest entry if the Software
Step state at the last exit was Active-pending.
Fixes: 337b99bf7edf ("KVM: arm64: guest debug, add support for single-step")
Signed-off-by: Reiji Watanabe <reijiw@google.com>
---
arch/arm64/include/asm/kvm_host.h | 3 +++
arch/arm64/kvm/debug.c | 19 ++++++++++++++++++-
arch/arm64/kvm/guest.c | 1 +
arch/arm64/kvm/handle_exit.c | 2 ++
4 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e9c9388ccc02..4cf6eef02565 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -535,6 +535,9 @@ struct kvm_vcpu_arch {
#define IN_WFIT __vcpu_single_flag(sflags, BIT(3))
/* vcpu system registers loaded on physical CPU */
#define SYSREGS_ON_CPU __vcpu_single_flag(sflags, BIT(4))
+/* Software step state is Active-pending */
+#define DBG_SS_ACTIVE_PENDING __vcpu_single_flag(sflags, BIT(5))
+
/* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
#define vcpu_sve_pffr(vcpu) (kern_hyp_va((vcpu)->arch.sve_state) + \
diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 0b28d7db7c76..125cfb94b4ad 100644
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -188,7 +188,16 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
* debugging the system.
*/
if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
- *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+ /*
+ * If the software step state at the last guest exit
+ * was Active-pending, we don't set DBG_SPSR_SS so
+ * that the state is maintained (to not run another
+ * single-step until the pending Software Step
+ * exception is taken).
+ */
+ if (!vcpu_get_flag(vcpu, DBG_SS_ACTIVE_PENDING))
+ *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
+
mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
mdscr |= DBG_MDSCR_SS;
vcpu_write_sys_reg(vcpu, mdscr, MDSCR_EL1);
@@ -279,6 +288,14 @@ void kvm_arm_clear_debug(struct kvm_vcpu *vcpu)
&vcpu->arch.debug_ptr->dbg_wcr[0],
&vcpu->arch.debug_ptr->dbg_wvr[0]);
}
+
+ if ((vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) &&
+ !(*vcpu_cpsr(vcpu) & DBG_SPSR_SS))
+ /*
+ * Mark the vcpu as ACTIVE_PENDING
+ * until Software Step exception is confirmed.
+ */
+ vcpu_set_flag(vcpu, DBG_SS_ACTIVE_PENDING);
}
}
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index f802a3b3f8db..2ff13a3f8479 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -937,6 +937,7 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
} else {
/* If not enabled clear all flags */
vcpu->guest_debug = 0;
+ vcpu_clear_flag(vcpu, DBG_SS_ACTIVE_PENDING);
}
out:
diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index bbe5b393d689..8e43b2668d67 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -154,6 +154,8 @@ static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu)
if (ESR_ELx_EC(esr) == ESR_ELx_EC_WATCHPT_LOW)
run->debug.arch.far = vcpu->arch.fault.far_el2;
+ else if (ESR_ELx_EC(esr) == ESR_ELx_EC_SOFTSTP_LOW)
+ vcpu_clear_flag(vcpu, DBG_SS_ACTIVE_PENDING);
return 0;
}
--
2.37.2.789.g6183377224-goog
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next prev parent reply other threads:[~2022-09-09 4:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-09 4:46 [PATCH 0/3] KVM: arm64: Fix a bug of single-step execution enabled by userspace Reiji Watanabe
2022-09-09 4:46 ` Reiji Watanabe [this message]
2022-09-09 12:41 ` [PATCH 1/3] KVM: arm64: Don't set PSTATE.SS when Software Step state is Active-pending Marc Zyngier
2022-09-10 4:12 ` Reiji Watanabe
2022-09-10 9:58 ` Marc Zyngier
2022-09-10 10:36 ` Marc Zyngier
2022-09-14 6:13 ` Reiji Watanabe
2022-09-14 8:12 ` Marc Zyngier
2022-09-09 4:46 ` [PATCH 2/3] KVM: arm64: selftests: Refactor debug-exceptions to make it amenable to new test cases Reiji Watanabe
2022-09-09 4:46 ` [PATCH 3/3] KVM: arm64: selftests: Add a test case for KVM_GUESTDBG_SINGLESTEP Reiji Watanabe
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