linux-kernel - Re: [PATCH 0/2] KVM: x86: Propagate AMD-specific IBRS bits to guests

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Message-ID: <20230228194153.46995-1-itazur@amazon.com>
Date:   Tue, 28 Feb 2023 19:41:53 +0000
From:   Takahiro Itazuri <itazur@...zon.com>
To:     <bp@...en8.de>
CC:     <dave.hansen@...ux.intel.com>, <itazur@...zon.com>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <mingo@...hat.com>, <pbonzini@...hat.com>, <seanjc@...gle.com>,
        <tglx@...utronix.de>, <x86@...nel.org>, <zulinx86@...il.com>
Subject: Re: [PATCH 0/2] KVM: x86: Propagate AMD-specific IBRS bits to guests

Date:   Tue, 28 Feb 2023 20:24:12 +0100
From:   Borislav Petkov <bp@...en8.de>
> I'd prefer if VMMs did supply whatever they prefer to the guests
> instead. None of those bits are used in the kernel for mitigations, as
> you've realized.

It is true that the kernel does not use those bits at all, but any
codes could be run inside guests.

One of examples is the following spectre/meltdown checker scipt used as
de facto standard.
https://github.com/speed47/spectre-meltdown-checker/blob/master/spectre-meltdown-checker.sh#L2768

Best regards,
Takahiro Itazuri