From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Nikolay Borisov <nik.borisov@suse.com>,
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>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
tony.luck@intel.com, ak@linux.intel.com,
tim.c.chen@linux.intel.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 v3 2/6] x86/entry_64: Add VERW just before userspace transition
Date: Thu, 26 Oct 2023 15:13:11 -0700 [thread overview]
Message-ID: <20231026221311.5dqmnmvq4pnpqswn@desk> (raw)
In-Reply-To: <20231026211508.tmd7hfniesiu53ps@desk>
On Thu, Oct 26, 2023 at 02:15:11PM -0700, Pawan Gupta wrote:
> On Thu, Oct 26, 2023 at 12:40:49PM -0700, Dave Hansen wrote:
> > On 10/26/23 12:29, Pawan Gupta wrote:
> > > On Thu, Oct 26, 2023 at 07:25:27PM +0300, Nikolay Borisov wrote:
> > >> On 25.10.23 г. 23:52 ч., Pawan Gupta wrote:
> > >>> @@ -1520,6 +1530,7 @@ SYM_CODE_START(ignore_sysret)
> > >>> UNWIND_HINT_END_OF_STACK
> > >>> ENDBR
> > >>> mov $-ENOSYS, %eax
> > >>> + CLEAR_CPU_BUFFERS
> > >> nit: Just out of curiosity is it really needed in this case or it's doesn
> > >> for the sake of uniformity so that all ring3 transitions are indeed
> > >> covered??
> > > Interrupts returning to kernel don't clear the CPU buffers. I believe
> > > interrupts will be enabled here, and getting an interrupt here could
> > > leak the data that interrupt touched.
> >
> > Specifically NMIs, right?
>
> Yes, and VERW can omitted for the same reason as NMI returning to
> kernel.
Thinking more on this, we should not omit verw here, as this spot is way
easier to target NMIs. A user executing SYSENTER in a loop has much
higher chances of causing an NMI to return to kernel, and skip verw.
next prev parent reply other threads:[~2023-10-26 22:13 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-25 20:52 [PATCH v3 0/6] Delay VERW Pawan Gupta
2023-10-25 20:52 ` [PATCH v3 1/6] x86/bugs: Add asm helpers for executing VERW Pawan Gupta
2023-10-25 21:10 ` Andrew Cooper
2023-10-25 21:28 ` Josh Poimboeuf
2023-10-25 21:30 ` Andrew Cooper
2023-10-25 21:49 ` Josh Poimboeuf
2023-10-25 22:07 ` Pawan Gupta
2023-10-25 22:13 ` Andrew Cooper
2023-10-27 13:48 ` Pawan Gupta
2023-10-27 14:12 ` Andrew Cooper
2023-10-27 14:24 ` Pawan Gupta
2023-10-26 13:44 ` Nikolay Borisov
2023-10-26 13:58 ` Andrew Cooper
2023-10-25 20:52 ` [PATCH v3 2/6] x86/entry_64: Add VERW just before userspace transition Pawan Gupta
2023-10-26 16:25 ` Nikolay Borisov
2023-10-26 19:29 ` Pawan Gupta
2023-10-26 19:40 ` Dave Hansen
2023-10-26 21:15 ` Pawan Gupta
2023-10-26 22:13 ` Pawan Gupta [this message]
2023-10-26 22:17 ` Dave Hansen
2023-10-25 20:53 ` [PATCH v3 3/6] x86/entry_32: " Pawan Gupta
2023-10-25 20:53 ` [PATCH v3 4/6] x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key Pawan Gupta
2023-10-25 20:53 ` [PATCH v3 5/6] KVM: VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH Pawan Gupta
2023-10-25 20:53 ` [PATCH v3 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation Pawan Gupta
2023-10-26 16:14 ` Nikolay Borisov
2023-10-26 19:07 ` Pawan Gupta
2023-10-26 19:30 ` Sean Christopherson
2023-10-26 20:17 ` Sean Christopherson
2023-10-26 21:27 ` Pawan Gupta
2023-10-26 20:48 ` Pawan Gupta
2023-10-26 21:22 ` Sean Christopherson
2023-10-26 22:03 ` Pawan Gupta
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