[PATCH] KVM: SVM: Mark SEV launch secret pages as dirty.

Cfir Cohen
2020-09-25T02:00:41Z

The LAUNCH_SECRET command performs encryption of the
launch secret memory contents. Mark pinned pages as
dirty, before unpinning them.
This matches the logic in sev_launch_update_data().

Fixes: 9c5e0afaf157 ("KVM: SVM: Add support for SEV LAUNCH_SECRET command")
Signed-off-by: Cfir Cohen <cfir@google.com>
---
Changelog since v2:
- Added 'Fixes' tag, updated comments.
Changelog since v1:
- Updated commit message.

arch/x86/kvm/svm/sev.c | 26 +++++++++++++++++---------
1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 5573a97f1520..55edaf3577a0 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -440,10 +440,8 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
}

/*
- * The LAUNCH_UPDATE command will perform in-place encryption of the
- * memory content (i.e it will write the same memory region with C=1).
- * It's possible that the cache may contain the data with C=0, i.e.,
- * unencrypted so invalidate it first.
+ * Flush (on non-coherent CPUs) before LAUNCH_UPDATE encrypts pages in
+ * place, the cache may contain data that was written unencrypted.
*/
sev_clflush_pages(inpages, npages);

@@ -799,10 +797,9 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
}

/*
- * The DBG_{DE,EN}CRYPT commands will perform {dec,en}cryption of the
- * memory content (i.e it will write the same memory region with C=1).
- * It's possible that the cache may contain the data with C=0, i.e.,
- * unencrypted so invalidate it first.
+ * Flush (on non-coherent CPUs) before DBG_{DE,EN}CRYPT reads or modifies
+ * the pages, flush the destination too in case the cache contains its
+ * current data.
*/
sev_clflush_pages(src_p, 1);
sev_clflush_pages(dst_p, 1);
@@ -850,7 +847,7 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
struct kvm_sev_launch_secret params;
struct page **pages;
void *blob, *hdr;
- unsigned long n;
+ unsigned long n, i;
int ret, offset;

if (!sev_guest(kvm))
@@ -863,6 +860,12 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
if (!pages)
return -ENOMEM;

+ /*
+ * Flush (on non-coherent CPUs) before LAUNCH_SECRET encrypts pages in
+ * place, the cache may contain data that was written unencrypted.
+ */
+ sev_clflush_pages(pages, n);
+
/*
* The secret must be copied into contiguous memory region, lets verify
* that userspace memory pages are contiguous before we issue command.
@@ -908,6 +911,11 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
e_free:
kfree(data);
e_unpin_memory:
+ /* content of memory is updated, mark pages dirty */
+ for (i = 0; i < n; i++) {
+ set_page_dirty_lock(pages[i]);
+ mark_page_accessed(pages[i]);
+ }
sev_unpin_memory(kvm, pages, n);
return ret;
}
--
2.28.0.681.g6f77f65b4e-goog