From: Paolo Bonzini <pbonzini@redhat.com>
To: Maxim Levitsky <mlevitsk@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kvm@vger.kernel.org, Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
David Matlack <dmatlack@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC] KVM: SVM: reduce guest MAXPHYADDR by one in case C-bit is a physical bit
Date: Mon, 18 Oct 2021 13:44:30 +0200 [thread overview]
Message-ID: <d23aa747-f962-fb5c-7ad7-9dc3277fe83e@redhat.com> (raw)
In-Reply-To: <eaddf15f13aa688c03d53831c2309a60957bb7f4.camel@redhat.com>
On 17/10/21 09:54, Maxim Levitsky wrote:
>
> I'll say, a hack to reduce it by 1 bit is still better that failing
> tests, at least until AMD explains to us, about what is going on.
What's going on is documented in the thread at
https://yhbt.net/lore/all/4f46f3ab-60e4-3118-1438-10a1e17cd900@suse.com/:
> That doesn't really follow what Andrew gave us, namely:
>
> 1) On parts with <40 bits, its fully hidden from software
>
> 2) Before Fam17h, it was always 12G just below 1T, even if there was
> more RAM above this location
>
> 3) On Fam17h and later, it is variable based on SME, and is either
> just below 2^48 (no encryption) or 2^43 (encryption)
If you can use this information to implement the fix, that'd be very
nice. I didn't apply the hackish fix because I wanted to test it on a
SME-enabled box.
Paolo
next prev parent reply other threads:[~2021-10-18 11:44 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-15 15:05 Vitaly Kuznetsov
2021-10-15 15:24 ` Sean Christopherson
2021-10-17 7:54 ` Maxim Levitsky
2021-10-18 7:42 ` Vitaly Kuznetsov
2021-10-18 11:44 ` Paolo Bonzini [this message]
2021-10-18 7:39 ` Vitaly Kuznetsov
2021-10-18 11:23 ` Vitaly Kuznetsov
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