From: Sean Christopherson <seanjc@google.com>
To: Yosry Ahmed <yosry.ahmed@linux.dev>
Cc: x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/6] KVM: nVMX: Always use IBPB to properly virtualize IBRS
Date: Tue, 25 Feb 2025 11:50:29 -0800 [thread overview]
Message-ID: <Z74fBQLeXxuiBC-U@google.com> (raw)
In-Reply-To: <20250219220826.2453186-6-yosry.ahmed@linux.dev>
On Wed, Feb 19, 2025, Yosry Ahmed wrote:
> On synthesized nested VM-exits in VMX, an IBPB is performed if IBRS is
> advertised to the guest to properly provide separate prediction domains
> for L1 and L2. However, this is currently conditional on
> X86_FEATURE_USE_IBPB, which depends on the host spectre_v2_user
> mitigation.
>
> In short, if spectre_v2_user=no, IBRS is not virtualized correctly and
> L1 becomes suspectible to attacks from L2. Fix this by performing the
> IBPB regardless of X86_FEATURE_USE_IBPB.
>
> Fixes: 2e7eab81425a ("KVM: VMX: Execute IBPB on emulated VM-exit when guest has IBRS")
> Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
> ---
Acked-by: Sean Christopherson <seanjc@google.com>
next prev parent reply other threads:[~2025-02-25 19:50 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-19 22:08 [PATCH 0/6] IBPB cleanups and a fixup Yosry Ahmed
2025-02-19 22:08 ` [PATCH 1/6] x86/bugs: Move the X86_FEATURE_USE_IBPB check into callers Yosry Ahmed
2025-02-25 19:47 ` Sean Christopherson
2025-02-25 21:28 ` Yosry Ahmed
2025-02-19 22:08 ` [PATCH 2/6] x86/mm: Remove X86_FEATURE_USE_IBPB checks in cond_mitigation() Yosry Ahmed
2025-02-19 22:08 ` [PATCH 3/6] x86/bugs: Remove the X86_FEATURE_USE_IBPB check in ib_prctl_set() Yosry Ahmed
2025-02-19 22:08 ` [PATCH 4/6] x86/bugs: Use a static branch to guard IBPB on vCPU load Yosry Ahmed
2025-02-25 19:49 ` Sean Christopherson
2025-02-25 21:27 ` Yosry Ahmed
2025-02-25 22:40 ` Sean Christopherson
2025-02-26 2:49 ` Yosry Ahmed
2025-02-27 0:46 ` Sean Christopherson
2025-02-27 0:54 ` Yosry Ahmed
2025-02-19 22:08 ` [PATCH 5/6] KVM: nVMX: Always use IBPB to properly virtualize IBRS Yosry Ahmed
2025-02-19 23:09 ` Jim Mattson
2025-02-25 19:50 ` Sean Christopherson [this message]
2025-02-19 22:08 ` [PATCH 6/6] x86/bugs: Remove X86_FEATURE_USE_IBPB Yosry Ahmed
2025-02-20 19:04 ` [PATCH 0/6] IBPB cleanups and a fixup Josh Poimboeuf
2025-02-20 19:59 ` Yosry Ahmed
2025-02-20 20:47 ` Josh Poimboeuf
2025-02-20 21:50 ` Yosry Ahmed
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