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Subject[PATCH RFC v7 27/64] crypto: ccp: Introduce snp leaked pages list
Date
From: Ashish Kalra <ashish.kalra@amd.com>

Pages are unsafe to be released back to the page-allocator, if they
have been transitioned to firmware/guest state and can't be reclaimed
or transitioned back to hypervisor/shared state. In this case add
them to an internal leaked pages list to ensure that they are not freed
or touched/accessed to cause fatal page faults.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
drivers/crypto/ccp/sev-dev.c | 28 ++++++++++++++++++++++++++++
include/linux/psp-sev.h | 8 ++++++++
2 files changed, 36 insertions(+)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 35f605936f1b..eca4e59b0f44 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -42,6 +42,12 @@
static DEFINE_MUTEX(sev_cmd_mutex);
static struct sev_misc_dev *misc_dev;

+/* list of pages which are leaked and cannot be reclaimed */
+static LIST_HEAD(snp_leaked_pages_list);
+static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
+
+static atomic_long_t snp_nr_leaked_pages = ATOMIC_LONG_INIT(0);
+
static int psp_cmd_timeout = 100;
module_param(psp_cmd_timeout, int, 0644);
MODULE_PARM_DESC(psp_cmd_timeout, " default timeout value, in seconds, for PSP commands");
@@ -188,6 +194,28 @@ static int sev_cmd_buffer_len(int cmd)
return 0;
}

+void snp_mark_pages_offline(unsigned long pfn, unsigned int npages)
+{
+ struct page *page = pfn_to_page(pfn);
+
+ WARN(1, "psc failed, pfn 0x%lx pages %d (marked offline)\n", pfn, npages);
+
+ spin_lock(&snp_leaked_pages_list_lock);
+ while (npages--) {
+ /*
+ * Reuse the page's buddy list for chaining into the leaked
+ * pages list. This page should not be on a free list currently
+ * and is also unsafe to be added to a free list.
+ */
+ list_add_tail(&page->buddy_list, &snp_leaked_pages_list);
+ sev_dump_rmpentry(pfn);
+ pfn++;
+ }
+ spin_unlock(&snp_leaked_pages_list_lock);
+ atomic_long_inc(&snp_nr_leaked_pages);
+}
+EXPORT_SYMBOL_GPL(snp_mark_pages_offline);
+
static void *sev_fw_alloc(unsigned long len)
{
struct page *page;
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 46f61e3ae33b..8edf5c548fbf 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -923,6 +923,12 @@ int sev_do_cmd(int cmd, void *data, int *psp_ret);

void *psp_copy_user_blob(u64 uaddr, u32 len);

+/**
+ * sev_mark_pages_offline - insert non-reclaimed firmware/guest pages
+ * into a leaked pages list.
+ */
+void snp_mark_pages_offline(unsigned long pfn, unsigned int npages);
+
#else /* !CONFIG_CRYPTO_DEV_SP_PSP */

static inline int
@@ -951,6 +957,8 @@ sev_issue_cmd_external_user(struct file *filep, unsigned int id, void *data, int

static inline void *psp_copy_user_blob(u64 __user uaddr, u32 len) { return ERR_PTR(-EINVAL); }

+void snp_mark_pages_offline(unsigned long pfn, unsigned int npages) {}
+
#endif /* CONFIG_CRYPTO_DEV_SP_PSP */

#endif /* __PSP_SEV_H__ */
--
2.25.1
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