From: Oliver Upton <oupton@kernel.org>
To: kvmarm@lists.linux.dev
Cc: Marc Zyngier <maz@kernel.org>, Joey Gouly <joey.gouly@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Wei-Lin Chang <weilin.chang@arm.com>,
Steffen Eiden <seiden@linux.ibm.com>,
Fuad Tabba <fuad.tabba@linux.dev>,
Leonardo Bras <leo.bras@arm.com>,
Oliver Upton <oupton@kernel.org>
Subject: [PATCH v2 27/28] KVM: arm64: Add tracepoints for S1 page table walk
Date: Fri, 23 Oct 2026 13:56:09 -0700 [thread overview]
Message-ID: <20261023205610.1044532-28-oupton@kernel.org> (raw)
In-Reply-To: <20261023205610.1044532-1-oupton@kernel.org>
MMU walk steps are a useful tidbit of information for KVM hackers. As
these events are far closer to modelling CPU architecture than exposing
KVM internals it clears the bar for adding tracepoints.
Signed-off-by: Oliver Upton <oupton@kernel.org>
---
arch/arm64/include/asm/kvm_nested.h | 8 +++++
arch/arm64/kvm/at.c | 18 +++++-----
arch/arm64/kvm/trace_arm.h | 52 +++++++++++++++++++++++++++++
3 files changed, 68 insertions(+), 10 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index 81d8b1676fe4..341604b619cc 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -343,6 +343,14 @@ struct s1_walk_info {
bool haft;
};
+struct s1_walk_step {
+ u64 desc;
+ u64 desc_ipa;
+ u64 desc_pa;
+ struct kvm_s2_trans s2_trans;
+ int level;
+};
+
struct s1_walk_result {
union {
struct {
diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
index 8f1be3af64e8..1a49eb3c288a 100644
--- a/arch/arm64/kvm/at.c
+++ b/arch/arm64/kvm/at.c
@@ -11,6 +11,8 @@
#include <asm/kvm_mmu.h>
#include <asm/lsui.h>
+#include "trace.h"
+
static int get_ia_size(struct s1_walk_info *wi)
{
return 64 - wi->txsz;
@@ -433,14 +435,6 @@ static int setup_s1_walk(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
return -EFAULT;
}
-struct s1_walk_step {
- u64 desc;
- u64 desc_ipa;
- u64 desc_pa;
- struct kvm_s2_trans s2_trans;
- int level;
-};
-
static int kvm_read_s1_desc(struct kvm_vcpu *vcpu, u64 pa, u64 *desc,
struct s1_walk_info *wi)
{
@@ -492,10 +486,10 @@ static int handle_desc_update(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
struct s1_walk_step *ws, struct s1_walk_result *wr,
struct kvm_walk_access *access)
{
- u64 old, new;
+ u64 old, old_cpu, new;
int ret;
- old = new = ws->desc;
+ old = old_cpu = new = ws->desc;
if (should_set_access_flag(wi, ws, access))
new |= PTE_AF;
@@ -529,6 +523,8 @@ static int handle_desc_update(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
return ret;
}
+ trace_kvm_s1_desc_update(ws, access->ia, old_cpu);
+
wr->desc = ws->desc;
wr->dirty = !(wr->desc & PTE_RDONLY);
return 0;
@@ -614,6 +610,8 @@ static int walk_s1(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
return ret;
}
+ trace_kvm_s1_walk_step(&ws, access->ia);
+
/* Invalid descriptor */
if (!(ws.desc & BIT(0)))
goto transfault;
diff --git a/arch/arm64/kvm/trace_arm.h b/arch/arm64/kvm/trace_arm.h
index 9c60f6465c78..9fe9b57f6fa8 100644
--- a/arch/arm64/kvm/trace_arm.h
+++ b/arch/arm64/kvm/trace_arm.h
@@ -415,6 +415,58 @@ TRACE_EVENT(kvm_forward_sysreg_trap,
sys_reg_Op2(__entry->sysreg))
);
+TRACE_EVENT(kvm_s1_walk_step,
+ TP_PROTO(struct s1_walk_step *ws, u64 ia),
+ TP_ARGS(ws, ia),
+
+ TP_STRUCT__entry(
+ __field(u64, ia)
+ __field(u64, desc)
+ __field(u64, ipa)
+ __field(u64, pa)
+ __field(int, level)
+ ),
+
+ TP_fast_assign(
+ __entry->ia = ia;
+ __entry->desc = ws->desc;
+ __entry->ipa = ws->desc_ipa;
+ __entry->pa = ws->desc_pa;
+ __entry->level = ws->level;
+ ),
+
+ TP_printk("ia: 0x%llx desc: 0x%llx ipa: 0x%llx pa: 0x%llx level: %d",
+ __entry->ia, __entry->desc, __entry->ipa, __entry->pa,
+ __entry->level)
+);
+
+TRACE_EVENT(kvm_s1_desc_update,
+ TP_PROTO(struct s1_walk_step *ws, u64 ia, u64 old),
+ TP_ARGS(ws, ia, old),
+
+ TP_STRUCT__entry(
+ __field(u64, ia)
+ __field(u64, new)
+ __field(u64, old)
+ __field(u64, ipa)
+ __field(u64, pa)
+ __field(int, level)
+ ),
+
+ TP_fast_assign(
+ __entry->ia = ia;
+ __entry->new = ws->desc;
+ __entry->old = old;
+ __entry->ipa = ws->desc_ipa;
+ __entry->pa = ws->desc_pa;
+ __entry->level = ws->level;
+ ),
+
+ TP_printk("ia: 0x%llx new: 0x%llx old: 0x%llx ipa: 0x%llx pa: 0x%llx level: %d",
+ __entry->ia, __entry->new, __entry->old, __entry->ipa,
+ __entry->pa, __entry->level)
+);
+
#endif /* _TRACE_ARM_ARM64_KVM_H */
#undef TRACE_INCLUDE_PATH
--
2.47.3
next prev parent reply other threads:[~2026-10-23 20:57 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-23 20:55 [PATCH v2 00/28] KVM: arm64: nv: Implement FEAT_HAFDBS, FEAT_HAFT Oliver Upton
2026-10-23 20:55 ` [PATCH v2 01/28] KVM: arm64: nv: Introduce struct for stage-2 walk step Oliver Upton
2026-10-23 20:55 ` [PATCH v2 02/28] KVM: arm64: nv: Consolidate computation of stage-2 permissions Oliver Upton
2026-10-23 20:55 ` [PATCH v2 03/28] KVM: arm64: nv: Get rid of kvm_s2_trans*() accessors Oliver Upton
2026-10-23 20:55 ` [PATCH v2 04/28] KVM: arm64: nv: Only shadow writable-dirty guest descs as writable Oliver Upton
2026-10-23 21:25 ` sashiko-bot
2026-10-24 6:26 ` Oliver Upton
2026-10-23 20:55 ` [PATCH v2 05/28] KVM: arm64: nv: Pass an access descriptor for stage-2 walks Oliver Upton
2026-10-23 20:55 ` [PATCH v2 06/28] KVM: arm64: nv: Use a helper for stage-2 descriptor updates Oliver Upton
2026-10-23 20:55 ` [PATCH v2 07/28] KVM: arm64: nv: Set dirty state at stage-2 Oliver Upton
2026-10-23 20:55 ` [PATCH v2 08/28] KVM: arm64: nv: Treat DBM as writable " Oliver Upton
2026-10-23 20:55 ` [PATCH v2 09/28] KVM: arm64: Compute S1 permissions as part of s1_walk() Oliver Upton
2026-10-23 20:55 ` [PATCH v2 10/28] KVM: arm64: Plumb through access descriptor for stage-1 Oliver Upton
2026-10-23 21:06 ` sashiko-bot
2026-10-23 20:55 ` [PATCH v2 11/28] KVM: arm64: Use a struct for stage-1 walk context Oliver Upton
2026-10-23 20:55 ` [PATCH v2 12/28] KVM: arm64: Create helper for stage-1 descriptor updates Oliver Upton
2026-10-23 20:55 ` [PATCH v2 13/28] KVM: arm64: Set dirty state at stage-1 Oliver Upton
2026-10-23 20:55 ` [PATCH v2 14/28] KVM: arm64: nv: Respect HA when computing translated TCR Oliver Upton
2026-10-23 20:55 ` [PATCH v2 15/28] KVM: arm64: nv: Respect HD " Oliver Upton
2026-10-23 20:55 ` [PATCH v2 16/28] KVM: arm64: Grant write permission when DBM is set at S1 Oliver Upton
2026-10-23 20:55 ` [PATCH v2 17/28] KVM: arm64: Don't update descriptors for "non-arch" access Oliver Upton
2026-10-23 20:56 ` [PATCH v2 18/28] KVM: arm64: nv: Emulate CMOs via writable-clean translations as NOPs Oliver Upton
2026-10-23 20:56 ` [PATCH v2 19/28] arm64: Add command line switch to disable FEAT_S2FWB Oliver Upton
2026-10-23 20:56 ` [PATCH v2 20/28] KVM: arm64: Reject non-coherent DMA when using forced writeback Oliver Upton
2026-10-23 21:16 ` sashiko-bot
2026-10-23 20:56 ` [PATCH v2 21/28] KVM: arm64: nv: Expose FEAT_HAFDBS Oliver Upton
2026-10-23 20:56 ` [PATCH v2 22/28] KVM: arm64: Set Access flag on table descriptors at stage-1 Oliver Upton
2026-10-23 21:22 ` sashiko-bot
2026-10-24 6:24 ` Oliver Upton
2026-10-23 20:56 ` [PATCH v2 23/28] KVM: arm64: nv: Set access flag on table descriptors at stage-2 Oliver Upton
2026-10-23 20:56 ` [PATCH v2 24/28] KVM: arm64: nv: Expose FEAT_HAFT Oliver Upton
2026-10-23 20:56 ` [PATCH v2 25/28] KVM: arm64: selftests: Only test AF behavior for emulated AT insns Oliver Upton
2026-10-23 20:56 ` [PATCH v2 26/28] KVM: arm64: selftests: Test AT emulation for FEAT_HAFT Oliver Upton
2026-10-23 20:56 ` Oliver Upton [this message]
2026-10-23 20:56 ` [PATCH v2 28/28] KVM: arm64: Add tracepoints for S2 page table walk Oliver Upton
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