From: Dave Hansen <dave.hansen@intel.com>
To: Josh Poimboeuf <jpoimboe@kernel.org>,
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, 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 2/6] x86/entry_64: Add VERW just before userspace transition
Date: Mon, 23 Oct 2023 12:17:21 -0700 [thread overview]
Message-ID: <caeebbb1-f733-4969-8eab-ce69ce35f4c4@intel.com> (raw)
In-Reply-To: <20231023182211.5ojm2rsoqqqwqg46@treble>
On 10/23/23 11:22, Josh Poimboeuf wrote:
> On Fri, Oct 20, 2023 at 01:45:03PM -0700, Pawan Gupta wrote:
>> + /* Mitigate CPU data sampling attacks .e.g. MDS */
>> + USER_CLEAR_CPU_BUFFERS
>> +
>> jmp .Lnative_iret
>>
>>
>> @@ -774,6 +780,9 @@ native_irq_return_ldt:
>> */
>> popq %rax /* Restore user RAX */
>>
>> + /* Mitigate CPU data sampling attacks .e.g. MDS */
>> + USER_CLEAR_CPU_BUFFERS
>> +
>
> I'm thinking the comments add unnecessary noise here. The macro name is
> self-documenting enough.
>
> The detail about what mitigations are being done can go above the macro
> definition itself, which the reader can refer to if they want more
> detail about what the macro is doing and why.
>
> Speaking of the macro name, I think just "CLEAR_CPU_BUFFERS" is
> sufficient. The "USER_" prefix makes it harder to read IMO.
Yes, please. The "USER_" prefix should be reserved for things that are
uniquely for the unambiguous return-to-userspace paths.
next prev parent reply other threads:[~2023-10-23 19:17 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-20 20:44 [PATCH 0/6] Delay VERW Pawan Gupta
2023-10-20 20:44 ` [PATCH 1/6] x86/bugs: Add asm helpers for executing VERW Pawan Gupta
2023-10-20 23:13 ` Sean Christopherson
2023-10-21 1:00 ` Pawan Gupta
2023-10-20 23:55 ` [RESEND][PATCH " Andrew Cooper
2023-10-21 1:18 ` Pawan Gupta
2023-10-21 1:33 ` Andrew Cooper
2023-10-21 2:21 ` Pawan Gupta
2023-10-23 18:08 ` Josh Poimboeuf
2023-10-23 19:09 ` Pawan Gupta
2023-10-25 6:28 ` Pawan Gupta
2023-10-25 7:22 ` Peter Zijlstra
2023-10-25 7:52 ` Andrew Cooper
2023-10-25 8:02 ` Peter Zijlstra
2023-10-25 15:27 ` Pawan Gupta
[not found] ` <6439a094-23a6-4de3-aa41-bd033163e044@citrix.com>
2023-10-22 16:16 ` [PATCH " Peter Zijlstra
2023-10-20 20:45 ` [PATCH 2/6] x86/entry_64: Add VERW just before userspace transition Pawan Gupta
2023-10-23 18:22 ` Josh Poimboeuf
2023-10-23 19:13 ` Pawan Gupta
2023-10-23 19:17 ` Dave Hansen [this message]
2023-10-23 18:35 ` Josh Poimboeuf
2023-10-23 21:04 ` Pawan Gupta
2023-10-23 21:47 ` Josh Poimboeuf
2023-10-23 22:30 ` Pawan Gupta
2023-10-23 22:45 ` Dave Hansen
2023-10-24 0:00 ` Pawan Gupta
2023-10-20 20:45 ` [PATCH 3/6] x86/entry_32: " Pawan Gupta
2023-10-20 23:49 ` Andi Kleen
2023-10-21 1:28 ` Pawan Gupta
2023-10-20 20:45 ` [PATCH 4/6] x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key Pawan Gupta
2023-10-23 18:48 ` Josh Poimboeuf
2023-10-23 21:09 ` Pawan Gupta
2023-10-20 20:45 ` [PATCH 5/6] x86/bugs: Cleanup mds_user_clear Pawan Gupta
2023-10-23 8:51 ` Nikolay Borisov
2023-10-23 16:06 ` Pawan Gupta
2023-10-20 20:45 ` [PATCH 6/6] KVM: VMX: Move VERW closer to VMentry for MDS mitigation Pawan Gupta
2023-10-20 22:55 ` Sean Christopherson
2023-10-21 0:46 ` Pawan Gupta
2023-10-23 14:58 ` Sean Christopherson
2023-10-23 17:05 ` Pawan Gupta
2023-10-23 18:56 ` Josh Poimboeuf
2023-10-23 21:17 ` Pawan Gupta
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