[PATCH v3 6/6] x86/sev: Add debugfs support for RMPOPT

[Ashish Kalra]

From: Ashish Kalra <ashish.kalra@xxxxxxx>

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@xxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
 arch/x86/virt/svm/sev.c | 107 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 107 insertions(+)

diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index 784c0e79200e..04d905894408 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -20,6 +20,8 @@
 #include <linux/amd-iommu.h>
 #include <linux/nospec.h>
 #include <linux/workqueue.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
 
 #include <asm/sev.h>
 #include <asm/processor.h>
@@ -143,6 +145,13 @@ static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
 
 static unsigned long snp_nr_leaked_pages;
 
+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
 
@@ -500,6 +509,8 @@ static inline bool __rmpopt(u64 rax, u64 rcx)
 		     : "a" (rax), "c" (rcx)
 		     : "memory", "cc");
 
+	assign_cpu(smp_processor_id(), &rmpopt_cpumask, optimized);
+
 	return optimized;
 }
 
@@ -514,6 +525,17 @@ static void rmpopt(void *val)
 	__rmpopt(rax, rcx);
 }
 
+/*
+ * 'val' is a system physical address.
+ */
+static void rmpopt_report_status(void *val)
+{
+	u64 rax = ALIGN_DOWN((u64)val, SZ_1G);
+	u64 rcx = RMPOPT_FUNC_REPORT_STATUS;
+
+	__rmpopt(rax, rcx);
+}
+
 static void rmpopt_work_handler(struct work_struct *work)
 {
 	phys_addr_t pa;
@@ -560,6 +582,89 @@ static void rmpopt_all_physmem(bool early)
 				   msecs_to_jiffies(RMPOPT_WORK_TIMEOUT));
 }
 
+/*
+ * 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), SZ_1G);
+	struct seq_paddr *p = seq->private;
+
+	if (*pos == 0) {
+		p->next_seq_paddr = ALIGN_DOWN(PFN_PHYS(min_low_pfn), SZ_1G);
+		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), SZ_1G);
+	phys_addr_t *curr_paddr = v;
+
+	(*pos)++;
+	if (*curr_paddr == end_paddr)
+		return NULL;
+	*curr_paddr += SZ_1G;
+
+	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 >> (get_order(SZ_1G) + PAGE_SHIFT));
+
+	cpumask_clear(&rmpopt_cpumask);
+	on_each_cpu_mask(cpu_online_mask, rmpopt_report_status,
+			 (void *)*curr_paddr, 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", arch_debugfs_dir);
+
+	debugfs_create_file("rmpopt-table", 0444, rmpopt_debugfs,
+			    NULL, &rmpopt_table_fops);
+}
+
 static __init void configure_and_enable_rmpopt(void)
 {
 	phys_addr_t pa_start = ALIGN_DOWN(PFN_PHYS(min_low_pfn), SZ_1G);
@@ -613,6 +718,8 @@ static __init void configure_and_enable_rmpopt(void)
 	 * optimizations on all physical memory.
 	 */
 	rmpopt_all_physmem(TRUE);
+
+	rmpopt_debugfs_setup();
 }
 
 /*
-- 
2.43.0