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ANDROID: KVM: arm64: Empty buffer support for hyp tracing trace file

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Previously, hyp/per_cpu/cpu*/trace files would return an error when no
buffer has been allocated (i.e. when no tracing has ever started).
Return an empty header instead.

Bug: 249050813
Change-Id: Ic88bbdf8c876b8f26101ce2b33d3aca26fb88c94
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
This commit is contained in:
Vincent Donnefort
2023-02-14 16:40:41 +00:00
parent 16d9a0f908
commit a7e5601e77
1 changed files with 16 additions and 11 deletions
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27
arch/arm64/kvm/hyp_trace.c
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@@ -398,6 +398,9 @@ static void *ht_next(struct seq_file *m, void *v, loff_t *pos)
(*pos)++;
if (!iter->buf_iter)
return NULL;
evt = ring_buffer_iter_peek(iter->buf_iter, &ts);
if (!evt)
return NULL;
@@ -415,7 +418,8 @@ static void *ht_start(struct seq_file *m, loff_t *pos)
struct ht_iterator *iter = m->private;
if (*pos == 0) {
ring_buffer_iter_reset(iter->buf_iter);
if (iter->buf_iter)
ring_buffer_iter_reset(iter->buf_iter);
(*pos)++;
iter->ent = NULL;
@@ -439,10 +443,12 @@ static int ht_show(struct seq_file *m, void *v)
struct ht_iterator *iter = v;
if (!iter->ent) {
unsigned long entries, overrun;
unsigned long entries = 0, overrun = 0;
entries = ring_buffer_entries_cpu(hyp_trace_buffer, iter->cpu);
overrun = ring_buffer_overrun_cpu(hyp_trace_buffer, iter->cpu);
if (hyp_trace_buffer) {
entries = ring_buffer_entries_cpu(hyp_trace_buffer, iter->cpu);
overrun = ring_buffer_overrun_cpu(hyp_trace_buffer, iter->cpu);
}
seq_printf(m, "# entries-in-buffer/entries-written: %lu/%lu\n",
entries, overrun + entries);
@@ -469,17 +475,15 @@ static int hyp_trace_open(struct inode *inode, struct file *file)
mutex_lock(&hyp_trace_lock);
if (!hyp_trace_buffer) {
ret = -ENODEV;
goto unlock;
}
iter = __seq_open_private(file, &hyp_trace_ops, sizeof(*iter));
if (!iter) {
ret = -ENOMEM;
goto unlock;
}
if (!hyp_trace_buffer)
goto unlock_and_read;
iter->buf_iter = ring_buffer_read_prepare(hyp_trace_buffer, cpu, GFP_KERNEL);
if (!iter->buf_iter) {
seq_release_private(inode, file);
@@ -491,7 +495,7 @@ static int hyp_trace_open(struct inode *inode, struct file *file)
ring_buffer_read_prepare_sync();
ring_buffer_read_start(iter->buf_iter);
unlock_and_read:
hyp_trace_readers++;
unlock:
mutex_unlock(&hyp_trace_lock);
@@ -504,7 +508,8 @@ int hyp_trace_release(struct inode *inode, struct file *file)
struct seq_file *m = file->private_data;
struct ht_iterator *iter = m->private;
ring_buffer_read_finish(iter->buf_iter);
if (iter->buf_iter)
ring_buffer_read_finish(iter->buf_iter);
mutex_lock(&hyp_trace_lock);
hyp_trace_readers--;