From: Sean Christopherson <seanjc@google.com>
To: Sasha Levin <sashal@kernel.org>
Cc: stable@vger.kernel.org
Subject: Re: [PATCH 6.12.y] KVM: VMX: Allow guest to set DEBUGCTL.RTM_DEBUG if RTM is supported
Date: Thu, 14 Aug 2025 09:16:29 -0700 [thread overview]
Message-ID: <aJ4L3UsGA8M_QO3C@google.com> (raw)
In-Reply-To: <20250813182455.2068642-1-sashal@kernel.org>
On Wed, Aug 13, 2025, Sasha Levin wrote:
> From: Sean Christopherson <seanjc@google.com>
>
> [ Upstream commit 17ec2f965344ee3fd6620bef7ef68792f4ac3af0 ]
>
> Let the guest set DEBUGCTL.RTM_DEBUG if RTM is supported according to the
> guest CPUID model, as debug support is supposed to be available if RTM is
> supported, and there are no known downsides to letting the guest debug RTM
> aborts.
>
> Note, there are no known bug reports related to RTM_DEBUG, the primary
> motivation is to reduce the probability of breaking existing guests when a
> future change adds a missing consistency check on vmcs12.GUEST_DEBUGCTL
> (KVM currently lets L2 run with whatever hardware supports; whoops).
>
> Note #2, KVM already emulates DR6.RTM, and doesn't restrict access to
> DR7.RTM.
>
> Fixes: 83c529151ab0 ("KVM: x86: expose Intel cpu new features (HLE, RTM) to guest")
> Cc: stable@vger.kernel.org
> Link: https://lore.kernel.org/r/20250610232010.162191-5-seanjc@google.com
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> [ Changed guest_cpu_cap_has to guest_cpuid_has ]
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
Acked-by: Sean Christopherson <seanjc@google.com>
prev parent reply other threads:[~2025-08-14 16:16 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-12 16:57 FAILED: patch "[PATCH] KVM: VMX: Allow guest to set DEBUGCTL.RTM_DEBUG if RTM is" failed to apply to 6.12-stable tree gregkh
2025-08-13 18:24 ` [PATCH 6.12.y] KVM: VMX: Allow guest to set DEBUGCTL.RTM_DEBUG if RTM is supported Sasha Levin
2025-08-14 16:16 ` Sean Christopherson [this message]
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