From: Dave Hansen <dave.hansen@intel.com>
To: Michael Kelley <mhklinux@outlook.com>,
Sean Christopherson <seanjc@google.com>,
Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Xi Ruoyao <xry111@xry111.site>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Dexuan Cui <decui@microsoft.com>
Subject: Re: [PATCH v2] x86/mm: Don't disable INVLPG if "incomplete Global INVLPG flushes" is fixed by microcode
Date: Thu, 4 Apr 2024 11:08:55 -0700 [thread overview]
Message-ID: <f8df14f3-ae6a-4e08-927a-7a7c2ebe8352@intel.com> (raw)
In-Reply-To: <SN6PR02MB415717D76F71C023A574841ED43C2@SN6PR02MB4157.namprd02.prod.outlook.com>
On 4/4/24 10:48, Michael Kelley wrote:
> I agree one could argue that it is a hypervisor bug to present PCID to the guest
> in this situation. It's a lot cleaner to not have a guest be checking FMS and
> microcode versions. But whether that's practical in the real world, at least
> for Hyper-V, I don't know. What's the real impact of running with PCID while
> the flaw is still present? I don’t know the history here ...
There's a chance that INVLPG will appear ineffective.
The bad sequence would go something like this: The kernel does the
INVLPG on a global mapping. Later, when switching PCIDs, the TLB entry
mysteriously reappears. No PCIDs switching means no mysterious
reappearance.
next prev parent reply other threads:[~2024-04-04 18:08 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-24 19:05 [PATCH v2] x86/mm: Don't disable INVLPG if "incomplete Global INVLPG flushes" is fixed by microcode Xi Ruoyao
2024-03-25 4:57 ` Michael Kelley
2024-03-25 10:21 ` Xi Ruoyao
2024-03-25 20:06 ` Michael Kelley
2024-03-25 21:41 ` Xi Ruoyao
2024-04-04 16:18 ` Sean Christopherson
2024-04-04 16:48 ` Andrew Cooper
2024-04-04 17:28 ` Sean Christopherson
2024-04-04 17:48 ` Michael Kelley
2024-04-04 18:08 ` Dave Hansen [this message]
2024-04-08 23:31 ` Michael Kelley
2024-04-09 1:43 ` Sean Christopherson
2024-04-09 7:56 ` Andrew Cooper
2024-04-11 5:38 ` Xi Ruoyao
2024-04-11 9:40 ` Andrew Cooper
2024-04-05 0:02 ` Andrew Cooper
2024-03-25 23:13 ` Pawan Gupta
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