From: Josh Poimboeuf <jpoimboe@kernel.org>
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>,
Andy Lutomirski <luto@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Sean Christopherson <seanjc@google.com>,
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,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH v4 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation
Date: Fri, 1 Dec 2023 12:02:47 -0800 [thread overview]
Message-ID: <20231201200247.vui6enzdj5nzctf4@treble> (raw)
In-Reply-To: <20231027-delay-verw-v4-6-9a3622d4bcf7@linux.intel.com>
On Fri, Oct 27, 2023 at 07:39:12AM -0700, Pawan Gupta wrote:
> - vmx_disable_fb_clear(vmx);
> + /*
> + * Optimize the latency of VERW in guests for MMIO mitigation. Skip
> + * the optimization when MDS mitigation(later in asm) is enabled.
> + */
> + if (!cpu_feature_enabled(X86_FEATURE_CLEAR_CPU_BUF))
> + vmx_disable_fb_clear(vmx);
>
> if (vcpu->arch.cr2 != native_read_cr2())
> native_write_cr2(vcpu->arch.cr2);
> @@ -7248,7 +7256,8 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
>
> vmx->idt_vectoring_info = 0;
>
> - vmx_enable_fb_clear(vmx);
> + if (!cpu_feature_enabled(X86_FEATURE_CLEAR_CPU_BUF))
> + vmx_enable_fb_clear(vmx);
>
It may be cleaner to instead check X86_FEATURE_CLEAR_CPU_BUF when
setting vmx->disable_fb_clear in the first place, in
vmx_update_fb_clear_dis().
--
Josh
next prev parent reply other threads:[~2023-12-01 20:03 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-27 14:38 [PATCH v4 0/6] Delay VERW Pawan Gupta
2023-10-27 14:38 ` [PATCH v4 1/6] x86/bugs: Add asm helpers for executing VERW Pawan Gupta
2023-10-27 15:32 ` Borislav Petkov
2023-11-02 0:01 ` Pawan Gupta
2023-12-01 19:36 ` Josh Poimboeuf
2023-12-01 19:39 ` Andrew Cooper
2023-12-01 20:04 ` Josh Poimboeuf
2023-12-20 1:15 ` Pawan Gupta
2023-10-27 14:38 ` [PATCH v4 2/6] x86/entry_64: Add VERW just before userspace transition Pawan Gupta
2023-10-27 14:38 ` [PATCH v4 3/6] x86/entry_32: " Pawan Gupta
2023-10-27 14:38 ` [PATCH v4 4/6] x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key Pawan Gupta
2023-12-01 19:59 ` Josh Poimboeuf
2023-12-20 1:20 ` Pawan Gupta
2023-10-27 14:39 ` [PATCH v4 5/6] KVM: VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH Pawan Gupta
2023-10-27 14:39 ` [PATCH v4 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation Pawan Gupta
2023-12-01 20:02 ` Josh Poimboeuf [this message]
2023-12-20 1:25 ` Pawan Gupta
2023-10-27 14:48 ` [PATCH v4 0/6] Delay VERW Borislav Petkov
2023-10-27 15:05 ` Pawan Gupta
2023-10-27 15:12 ` Borislav Petkov
2023-10-27 15:32 ` Pawan Gupta
2023-10-27 15:36 ` Borislav Petkov
2023-10-27 15:38 ` Greg Kroah-Hartman
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