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

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Message-Id: <20200807012303.3769170-1-cfir@google.com>
Date:   Thu,  6 Aug 2020 18:23:03 -0700
From:   Cfir Cohen <cfir@...gle.com>
To:     "kvm @ vger . kernel . org" <kvm@...r.kernel.org>,
        Lendacky Thomas <thomas.lendacky@....com>,
        Singh Brijesh <brijesh.singh@....com>
Cc:     Grimm Jon <Jon.Grimm@....com>,
        David Rientjes <rientjes@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Cfir Cohen <cfir@...gle.com>
Subject: [PATCH] KVM: SVM: Mark SEV launch secret pages as dirty.

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().

Signed-off-by: Cfir Cohen <cfir@...gle.com>
---
 arch/x86/kvm/svm/sev.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 5573a97f1520..37c47d26b9f7 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -850,7 +850,7 @@ 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 +863,14 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	if (!pages)
 		return -ENOMEM;
 
+	/*
+	 * 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.
+	 */
+	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 +916,11 @@ 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;
 }
-- 
2.28.0.163.g6104cc2f0b6-goog