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From: Michael Roth <michael.roth@amd.com>
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Subject: [PATCH v1 15/26] x86/sev: Introduce snp leaked pages list
Date: Sat, 30 Dec 2023 10:19:43 -0600
Message-ID: <20231230161954.569267-16-michael.roth@amd.com>
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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>
[mdr: relocate to arch/x86/virt/svm/sev.c]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 arch/x86/include/asm/sev.h |  2 ++
 arch/x86/virt/svm/sev.c    | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index d3ccb7a0c7e9..435ba9bc4510 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -264,6 +264,7 @@ void snp_dump_hva_rmpentry(unsigned long address);
 int psmash(u64 pfn);
 int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable);
 int rmp_make_shared(u64 pfn, enum pg_level level);
+void snp_leak_pages(u64 pfn, unsigned int npages);
 #else
 static inline bool snp_probe_rmptable_info(void) { return false; }
 static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENODEV; }
@@ -275,6 +276,7 @@ static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int as
 	return -ENODEV;
 }
 static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; }
+static inline void snp_leak_pages(u64 pfn, unsigned int npages) {}
 #endif
 
 #endif
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index ee182351d93a..0f2e1ce241b5 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -60,6 +60,17 @@ static u64 probed_rmp_base, probed_rmp_size;
 static struct rmpentry *rmptable __ro_after_init;
 static u64 rmptable_max_pfn __ro_after_init;
 
+/* List of pages which are leaked and cannot be reclaimed */
+struct leaked_page {
+	struct page *page;
+	struct list_head list;
+};
+
+static LIST_HEAD(snp_leaked_pages_list);
+static DEFINE_SPINLOCK(snp_leaked_pages_list_lock);
+
+static unsigned long snp_nr_leaked_pages;
+
 #undef pr_fmt
 #define pr_fmt(fmt)	"SEV-SNP: " fmt
 
@@ -476,3 +487,27 @@ int rmp_make_shared(u64 pfn, enum pg_level level)
 	return rmpupdate(pfn, &state);
 }
 EXPORT_SYMBOL_GPL(rmp_make_shared);
+
+void snp_leak_pages(u64 pfn, unsigned int npages)
+{
+	struct page *page = pfn_to_page(pfn);
+	struct leaked_page *leak;
+
+	pr_debug("%s: leaking PFN range 0x%llx-0x%llx\n", __func__, pfn, pfn + npages);
+
+	spin_lock(&snp_leaked_pages_list_lock);
+	while (npages--) {
+		leak = kzalloc(sizeof(*leak), GFP_KERNEL_ACCOUNT);
+		if (!leak)
+			goto unlock;
+		leak->page = page;
+		list_add_tail(&leak->list, &snp_leaked_pages_list);
+		dump_rmpentry(pfn);
+		snp_nr_leaked_pages++;
+		pfn++;
+		page++;
+	}
+unlock:
+	spin_unlock(&snp_leaked_pages_list_lock);
+}
+EXPORT_SYMBOL_GPL(snp_leak_pages);
-- 
2.25.1