From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Tom Lendacky <thomas.lendacky@amd.com>,
Weijiang Yang <weijiang.yang@intel.com>
Subject: [PATCH 01/10] KVM: SVM: Disallow guest from changing userspace's MSR_AMD64_DE_CFG value
Date: Thu, 25 Apr 2024 11:14:13 -0700 [thread overview]
Message-ID: <20240425181422.3250947-2-seanjc@google.com> (raw)
In-Reply-To: <20240425181422.3250947-1-seanjc@google.com>
Inject a #GP if the guest attempts to change MSR_AMD64_DE_CFG from its
*current* value, not if the guest attempts to write a value other than
KVM's set of supported bits. As per the comment and the changelog of the
original code, the intent is to effectively make MSR_AMD64_DE_CFG read-
only for the guest.
Opportunistically use a more conventional equality check instead of an
exclusive-OR check to detect attempts to change bits.
Fixes: d1d93fa90f1a ("KVM: SVM: Add MSR-based feature support for serializing LFENCE")
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/svm.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 0f3b59da0d4a..00f0c0b506d4 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -3142,8 +3142,13 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
if (data & ~msr_entry.data)
return 1;
- /* Don't allow the guest to change a bit, #GP */
- if (!msr->host_initiated && (data ^ msr_entry.data))
+ /*
+ * Don't let the guest change the host-programmed value. The
+ * MSR is very model specific, i.e. contains multiple bits that
+ * are completely unknown to KVM, and the one bit known to KVM
+ * is simply a reflection of hardware capatibilies.
+ */
+ if (!msr->host_initiated && data != svm->msr_decfg)
return 1;
svm->msr_decfg = data;
--
2.44.0.769.g3c40516874-goog
next prev parent reply other threads:[~2024-04-25 18:14 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-25 18:14 [PATCH 00/10] KVM: x86: Clean up MSR access/failure handling Sean Christopherson
2024-04-25 18:14 ` Sean Christopherson [this message]
2024-04-25 18:14 ` [PATCH 02/10] KVM: x86: Move MSR_TYPE_{R,W,RW} values from VMX to x86, as enums Sean Christopherson
2024-04-25 18:14 ` [PATCH 03/10] KVM: x86: Rename KVM_MSR_RET_INVALID to KVM_MSR_RET_UNSUPPORTED Sean Christopherson
2024-04-25 18:14 ` [PATCH 04/10] KVM: x86: Refactor kvm_x86_ops.get_msr_feature() to avoid kvm_msr_entry Sean Christopherson
2024-04-25 18:14 ` [PATCH 05/10] KVM: x86: Rename get_msr_feature() APIs to get_feature_msr() Sean Christopherson
2024-04-26 6:58 ` Yang, Weijiang
2024-04-25 18:14 ` [PATCH 06/10] KVM: x86: Refactor kvm_get_feature_msr() to avoid struct kvm_msr_entry Sean Christopherson
2024-04-25 18:14 ` [PATCH 07/10] KVM: x86: Funnel all fancy MSR return value handling into a common helper Sean Christopherson
2024-04-25 18:14 ` [PATCH 08/10] KVM: x86: Hoist x86.c's global msr_* variables up above kvm_do_msr_access() Sean Christopherson
2024-04-25 18:14 ` [PATCH 09/10] KVM: x86: Suppress failures on userspace access to advertised, unsupported MSRs Sean Christopherson
2024-04-26 12:36 ` Yang, Weijiang
2024-04-26 17:18 ` Sean Christopherson
2024-04-25 18:14 ` [PATCH 10/10] KVM: x86: Suppress userspace access failures on unsupported, "emulated" MSRs Sean Christopherson
2024-04-26 7:43 ` Yang, Weijiang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240425181422.3250947-2-seanjc@google.com \
--to=seanjc@google.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pbonzini@redhat.com \
--cc=thomas.lendacky@amd.com \
--cc=weijiang.yang@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).