linux-kernel - [PATCH v15 16/20] KVM: SEV: Avoid WBINVD for HVA-based MMU notifications for SNP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240501085210.2213060-17-michael.roth@amd.com>
Date: Wed, 1 May 2024 03:52:06 -0500
From: Michael Roth <michael.roth@....com>
To: <kvm@...r.kernel.org>
CC: <linux-coco@...ts.linux.dev>, <linux-mm@...ck.org>,
	<linux-crypto@...r.kernel.org>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<jroedel@...e.de>, <thomas.lendacky@....com>, <hpa@...or.com>,
	<ardb@...nel.org>, <pbonzini@...hat.com>, <seanjc@...gle.com>,
	<vkuznets@...hat.com>, <jmattson@...gle.com>, <luto@...nel.org>,
	<dave.hansen@...ux.intel.com>, <slp@...hat.com>, <pgonda@...gle.com>,
	<peterz@...radead.org>, <srinivas.pandruvada@...ux.intel.com>,
	<rientjes@...gle.com>, <dovmurik@...ux.ibm.com>, <tobin@....com>,
	<bp@...en8.de>, <vbabka@...e.cz>, <kirill@...temov.name>,
	<ak@...ux.intel.com>, <tony.luck@...el.com>,
	<sathyanarayanan.kuppuswamy@...ux.intel.com>, <alpergun@...gle.com>,
	<jarkko@...nel.org>, <ashish.kalra@....com>, <nikunj.dadhania@....com>,
	<pankaj.gupta@....com>, <liam.merwick@...cle.com>
Subject: [PATCH v15 16/20] KVM: SEV: Avoid WBINVD for HVA-based MMU notifications for SNP

From: Ashish Kalra <ashish.kalra@....com>

With SNP/guest_memfd, private/encrypted memory should not be mappable,
and MMU notifications for HVA-mapped memory will only be relevant to
unencrypted guest memory. Therefore, the rationale behind issuing a
wbinvd_on_all_cpus() in sev_guest_memory_reclaimed() should not apply
for SNP guests and can be ignored.

Signed-off-by: Ashish Kalra <ashish.kalra@....com>
Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
[mdr: Add some clarifications in commit]
Signed-off-by: Michael Roth <michael.roth@....com>
---
 arch/x86/kvm/svm/sev.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 224fdab32950..e94e3aa4d932 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3039,7 +3039,13 @@ static void sev_flush_encrypted_page(struct kvm_vcpu *vcpu, void *va)
 
 void sev_guest_memory_reclaimed(struct kvm *kvm)
 {
-	if (!sev_guest(kvm))
+	/*
+	 * With SNP+gmem, private/encrypted memory is unreachable via the
+	 * hva-based mmu notifiers, so these events are only actually
+	 * pertaining to shared pages where there is no need to perform
+	 * the WBINVD to flush associated caches.
+	 */
+	if (!sev_guest(kvm) || sev_snp_guest(kvm))
 		return;
 
 	wbinvd_on_all_cpus();
-- 
2.25.1