Very similar content is present in four comments in sev.c. Unfortunately there are small differences that make it harder to place the comment in sev_clflush_pages itself, but at least we can make it more concise.
Suggested-by: Sean Christopherson <[email protected]> Signed-off-by: Paolo Bonzini <[email protected]> --- arch/x86/kvm/svm/sev.c | 19 +++++++------------ 1 file changed, 7 insertions(+), 12 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index bb0e89c79a04..65e15c22bd3c 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -446,10 +446,8 @@ 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 the data that was written unencrypted. */ sev_clflush_pages(inpages, npages); @@ -805,10 +803,9 @@ 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 read or modify + * the pages; flush the destination too so that future accesses do not + * see stale data. */ sev_clflush_pages(src_p, 1); sev_clflush_pages(dst_p, 1); @@ -870,10 +867,8 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp) return PTR_ERR(pages); /* - * The LAUNCH_SECRET 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_SECRET encrypts pages in + * place; the cache may contain the data that was written unencrypted. */ sev_clflush_pages(pages, n); -- 2.26.2
