From: Sean Christopherson <seanjc@google.com>
To: Sasha Levin <sashal@kernel.org>
Cc: stable@vger.kernel.org, Yosry Ahmed <yosry@kernel.org>
Subject: Re: [PATCH 6.12.y] KVM: x86: Disallow EFER.LME and EFER.LMA if long mode is not supported
Date: Fri, 11 Sep 2026 07:22:38 -0700 [thread overview]
Message-ID: <aqQOroJmp1a3n-0W@google.com> (raw)
In-Reply-To: <20260911120502.489632-1-sashal@kernel.org>
On Fri, Sep 11, 2026, Sasha Levin wrote:
> From: Yosry Ahmed <yosry@kernel.org>
>
> [ Upstream commit e62392bf39ebfdf60d1d082799397fe1cbf8dfc5 ]
>
> Remove EFER.LME and EFER.LMA from EFER reserved bits only if long mode
> is actually supported. KVM does check long-mode support before allowing
> the bits for guest writes and userspace writes through KVM_SET_SREGS*
> (in __kvm_valid_efer()), but userspace writes through KVM_SET_MSRS only
> check reserved bits.
>
> In practice, this doesn't really matter. The true motiviation is getting
> rid of the #ifdeffery when initializing efer_reserved_bits.
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Yosry Ahmed <yosry@kernel.org>
> Link: https://patch.msgid.link/20260713181020.2735367-3-yosry@kernel.org
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> [ adapted EFER changes to x86.c, placing the capability check in kvm_x86_vendor_init() because kvm_setup_efer_caps() is absent. ]
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
Acked-by: Sean Christopherson <seanjc@google.com>
prev parent reply other threads:[~2026-09-11 14:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-09 10:32 FAILED: patch "[PATCH] KVM: x86: Disallow EFER.LME and EFER.LMA if long mode is not" failed to apply to 6.12-stable tree gregkh
2026-09-11 12:05 ` [PATCH 6.12.y] KVM: x86: Disallow EFER.LME and EFER.LMA if long mode is not supported Sasha Levin
2026-09-11 14:22 ` Sean Christopherson [this message]
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