From: Paolo Bonzini <pbonzini@redhat.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH] SPTE masking
Date: Sun, 12 Aug 2018 12:57:29 +0200 [thread overview]
Message-ID: <31468c4e-f66c-83c1-3591-fff08cb1b420@redhat.com> (raw)
In-Reply-To: <20180810191747.GJ4238@tassilo.jf.intel.com>
[-- Attachment #1: Type: text/plain, Size: 926 bytes --]
On 10/08/2018 21:17, speck for Andi Kleen wrote:
>> l1tf-maxphyaddr is the real maxphyaddr, cpuid-maxphyaddr is the lower
>> fake one reported by the CPU.
>
> It's not fake, it's what the bus supports.
>
>>
>> If they are equal, you need to ensure that your nonpresent PTEs use
>> unused/uncacheable portions of the address space. If they are not
>> equal, you can use some of those reserved bits that exist in the cache
>> but not in the PTEs.
>
> Right, but we always use upto 46 because we have to anyways because
> of the lying VMs. And with 46 we're always safe on all current parts,
> because it's guaranteed to be >= l1tf-maxphyaddr.
For KVM the problem is the opposite, if l1tf-maxphyaddr ==
cpuid-maxphyaddr you can end up with a cacheable frame number in invalid
PTEs.
Perhaps the simplest fix is to also do inversion. I'll send a patch
next week after everything is public.
Paolo
next prev parent reply other threads:[~2018-08-12 10:57 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-08 23:21 [MODERATED] [PATCH] SPTE masking Jim Mattson
2018-08-09 2:57 ` [MODERATED] " Andi Kleen
2018-08-09 9:24 ` Paolo Bonzini
2018-08-09 17:43 ` Andi Kleen
2018-08-10 7:55 ` Paolo Bonzini
2018-08-10 15:59 ` Jim Mattson
2018-08-10 17:23 ` Andi Kleen
2018-08-10 17:32 ` Linus Torvalds
2018-08-10 17:45 ` Andi Kleen
2018-08-10 18:37 ` Paolo Bonzini
2018-08-10 19:17 ` Andi Kleen
2018-08-12 10:57 ` Paolo Bonzini [this message]
2018-08-09 9:25 ` Paolo Bonzini
2018-08-09 9:33 ` Andrew Cooper
2018-08-09 10:01 ` Paolo Bonzini
2018-08-09 10:47 ` Andrew Cooper
2018-08-09 11:13 ` Paolo Bonzini
2018-08-09 11:46 ` Andrew Cooper
2018-08-09 11:54 ` Paolo Bonzini
2018-08-09 14:01 ` Andrew Cooper
2018-08-09 15:00 ` Paolo Bonzini
2018-08-09 20:14 ` Jim Mattson
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