From: Sean Christopherson <seanjc@google.com>
To: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Paolo Bonzini <pbonzini@redhat.com>,
tony.luck@intel.com, ak@linux.intel.com,
tim.c.chen@linux.intel.com,
Andrew Cooper <andrew.cooper3@citrix.com>,
Nikolay Borisov <nik.borisov@suse.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
kvm@vger.kernel.org,
Alyssa Milburn <alyssa.milburn@linux.intel.com>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
antonio.gomez.iglesias@linux.intel.com
Subject: Re: [PATCH v6 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation
Date: Fri, 26 Jan 2024 13:31:54 -0800 [thread overview]
Message-ID: <ZbQkyr8c12jOqWQ-@google.com> (raw)
In-Reply-To: <20240123-delay-verw-v6-6-a8206baca7d3@linux.intel.com>
On Tue, Jan 23, 2024, Pawan Gupta wrote:
> During VMentry VERW is executed to mitigate MDS. After VERW, any memory
> access like register push onto stack may put host data in MDS affected
> CPU buffers. A guest can then use MDS to sample host data.
>
> Although likelihood of secrets surviving in registers at current VERW
> callsite is less, but it can't be ruled out. Harden the MDS mitigation
> by moving the VERW mitigation late in VMentry path.
>
> Note that VERW for MMIO Stale Data mitigation is unchanged because of
> the complexity of per-guest conditional VERW which is not easy to handle
> that late in asm with no GPRs available. If the CPU is also affected by
> MDS, VERW is unconditionally executed late in asm regardless of guest
> having MMIO access.
>
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
> ---
Acked-by: Sean Christopherson <seanjc@google.com>
next prev parent reply other threads:[~2024-01-26 21:31 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-24 7:40 [PATCH v6 0/6] Delay VERW Pawan Gupta
2024-01-24 7:41 ` [PATCH v6 1/6] x86/bugs: Add asm helpers for executing VERW Pawan Gupta
2024-02-01 1:18 ` Pawan Gupta
2024-02-02 3:29 ` Josh Poimboeuf
2024-02-02 21:31 ` Pawan Gupta
2024-01-24 7:41 ` [PATCH v6 2/6] x86/entry_64: Add VERW just before userspace transition Pawan Gupta
2024-01-24 7:41 ` [PATCH v6 3/6] x86/entry_32: " Pawan Gupta
2024-01-24 7:41 ` [PATCH v6 4/6] x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key Pawan Gupta
2024-01-24 7:42 ` [PATCH v6 5/6] KVM: VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH Pawan Gupta
2024-01-24 7:42 ` [PATCH v6 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation Pawan Gupta
2024-01-26 21:31 ` Sean Christopherson [this message]
2024-02-01 1:12 ` Pawan Gupta
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