[PATCH v1 15/26] x86/sev: Introduce snp leaked pages list

Michael Roth
2023-12-30T16:23:54Z

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