linux-kernel - [PATCH RFC v7 27/64] crypto: ccp: Introduce snp leaked pages list

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Date:   Wed, 14 Dec 2022 13:40:19 -0600
From:   Michael Roth <michael.roth@....com>
To:     <kvm@...r.kernel.org>
CC:     <linux-coco@...ts.linux.dev>, <linux-mm@...ck.org>,
        <linux-crypto@...r.kernel.org>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <jroedel@...e.de>, <thomas.lendacky@....com>,
        <hpa@...or.com>, <ardb@...nel.org>, <pbonzini@...hat.com>,
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        <alpergun@...gle.com>, <dgilbert@...hat.com>, <jarkko@...nel.org>,
        <ashish.kalra@....com>, <harald@...fian.com>
Subject: [PATCH RFC v7 27/64] crypto: ccp: Introduce snp leaked pages list

From: Ashish Kalra <ashish.kalra@....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@....com>
Signed-off-by: Michael Roth <michael.roth@....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