[PATCH 6/6] x86/sev: Add debugfs support for RMPOPT

[Ashish Kalra <Ashish.Kalra@amd.com>]

From: Ashish Kalra <ashish.kalra@amd.com>

Add a debugfs interface to report per-CPU RMPOPT status across all
system RAM.

To dump the per-CPU RMPOPT status for all system RAM:

/sys/kernel/debug/rmpopt# cat rmpopt-table

Memory @  0GB: CPU(s): none
Memory @  1GB: CPU(s): none
Memory @  2GB: CPU(s): 0-1023
Memory @  3GB: CPU(s): 0-1023
Memory @  4GB: CPU(s): none
Memory @  5GB: CPU(s): 0-1023
Memory @  6GB: CPU(s): 0-1023
Memory @  7GB: CPU(s): 0-1023
...
Memory @1025GB: CPU(s): 0-1023
Memory @1026GB: CPU(s): 0-1023
Memory @1027GB: CPU(s): 0-1023
Memory @1028GB: CPU(s): 0-1023
Memory @1029GB: CPU(s): 0-1023
Memory @1030GB: CPU(s): 0-1023
Memory @1031GB: CPU(s): 0-1023
Memory @1032GB: CPU(s): 0-1023
Memory @1033GB: CPU(s): 0-1023
Memory @1034GB: CPU(s): 0-1023
Memory @1035GB: CPU(s): 0-1023
Memory @1036GB: CPU(s): 0-1023
Memory @1037GB: CPU(s): 0-1023
Memory @1038GB: CPU(s): none

Suggested-by: Thomas Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 arch/x86/virt/svm/sev.c | 101 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 100 insertions(+), 1 deletion(-)

diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index 0f71a045e4aa..c5a11f574e42 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -21,6 +21,8 @@
 #include <linux/nospec.h>
 #include <linux/kthread.h>
 #include <linux/configfs.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
 
 #include <asm/sev.h>
 #include <asm/processor.h>
@@ -151,6 +153,13 @@ struct rmpopt_socket_config {
 
 static atomic_t rmpopt_in_progress = ATOMIC_INIT(0);
 
+static cpumask_t rmpopt_cpumask;
+static struct dentry *rmpopt_debugfs;
+
+struct seq_paddr {
+	phys_addr_t next_seq_paddr;
+};
+
 #undef pr_fmt
 #define pr_fmt(fmt)	"SEV-SNP: " fmt
 
@@ -547,9 +556,14 @@ static void get_cpumask_of_primary_threads(cpumask_var_t cpulist)
  */
 static void rmpopt(void *val)
 {
+	bool optimized;
+
 	asm volatile(".byte 0xf2, 0x0f, 0x01, 0xfc\n\t"
-		     : : "a" ((u64)val & PUD_MASK), "c" ((u64)val & 0x1)
+		     : "=@ccc" (optimized)
+		     : "a" ((u64)val & PUD_MASK), "c" ((u64)val & 0x1)
 		     : "memory", "cc");
+
+	assign_cpu(smp_processor_id(), &rmpopt_cpumask, optimized);
 }
 
 static int rmpopt_kthread(void *__unused)
@@ -672,6 +686,89 @@ static int rmpopt_configfs_setup(void)
 	return ret;
 }
 
+/*
+ * start() can be called multiple times if allocated buffer has overflowed
+ * and bigger buffer is allocated.
+ */
+static void *rmpopt_table_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	phys_addr_t end_paddr = ALIGN(PFN_PHYS(max_pfn), PUD_SIZE);
+	struct seq_paddr *p = seq->private;
+
+	if (*pos == 0) {
+		p->next_seq_paddr = ALIGN_DOWN(PFN_PHYS(min_low_pfn), PUD_SIZE);
+		return &p->next_seq_paddr;
+	}
+
+	if (p->next_seq_paddr == end_paddr)
+		return NULL;
+
+	return &p->next_seq_paddr;
+}
+
+static void *rmpopt_table_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	phys_addr_t end_paddr = ALIGN(PFN_PHYS(max_pfn), PUD_SIZE);
+	phys_addr_t *curr_paddr = v;
+
+	(*pos)++;
+	if (*curr_paddr == end_paddr)
+		return NULL;
+	*curr_paddr += PUD_SIZE;
+
+	return curr_paddr;
+}
+
+static void rmpopt_table_seq_stop(struct seq_file *seq, void *v)
+{
+}
+
+static int rmpopt_table_seq_show(struct seq_file *seq, void *v)
+{
+	phys_addr_t *curr_paddr = v;
+
+	seq_printf(seq, "Memory @%3lluGB: ", *curr_paddr >> PUD_SHIFT);
+
+	cpumask_clear(&rmpopt_cpumask);
+	on_each_cpu_mask(cpu_online_mask, rmpopt,
+			 (void *)(*curr_paddr | RMPOPT_FUNC_REPORT_STATUS),
+			 true);
+
+	if (cpumask_empty(&rmpopt_cpumask))
+		seq_puts(seq, "CPU(s): none\n");
+	else
+		seq_printf(seq, "CPU(s): %*pbl\n", cpumask_pr_args(&rmpopt_cpumask));
+
+	return 0;
+}
+
+static const struct seq_operations rmpopt_table_seq_ops = {
+	.start = rmpopt_table_seq_start,
+	.next = rmpopt_table_seq_next,
+	.stop = rmpopt_table_seq_stop,
+	.show = rmpopt_table_seq_show
+};
+
+static int rmpopt_table_open(struct inode *inode, struct file *file)
+{
+	return seq_open_private(file, &rmpopt_table_seq_ops, sizeof(struct seq_paddr));
+}
+
+static const struct file_operations rmpopt_table_fops = {
+	.open = rmpopt_table_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = seq_release_private,
+};
+
+static void rmpopt_debugfs_setup(void)
+{
+	rmpopt_debugfs = debugfs_create_dir("rmpopt", NULL);
+
+	debugfs_create_file("rmpopt-table", 0444, rmpopt_debugfs,
+			    NULL, &rmpopt_table_fops);
+}
+
 static void __configure_rmpopt(void *val)
 {
 	u64 rmpopt_base = ((u64)val & PUD_MASK) | MSR_AMD64_RMPOPT_ENABLE;
@@ -849,6 +946,8 @@ static __init void configure_and_enable_rmpopt(void)
 
 	rmpopt_configfs_setup();
 
+	rmpopt_debugfs_setup();
+
 free_cpumask:
 	free_cpumask_var(primary_threads_cpulist);
 }
-- 
2.43.0