From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7292315278E; Fri, 13 Jun 2025 17:59:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749837554; cv=none; b=VfZd8IDnR2+7CBzeJ4y/W5JlUDn7f9nU+CwNvGyP18rUbx9wP7YNnfROAqwCRCyzVqn0wht2UiDm92/z/UrIC5VbijGqjvw9ZnseZ88zJ3jxTxSEkqg2oq7wjIUKoZiHdjDqv4nAQFpTYA2LMStqVzMQEvIHP1wmcdjblHgm9Ds= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749837554; c=relaxed/simple; bh=wFwsG2FRP6Do8TYFgbHwzgecKIiezlLARp1LI18nxQM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Y+shGO+vpi4glV6BNmJKPzba6iXZL4ww+EjWDlDFRG0gAl00JH5QZfCUbCoANTKysF/Tq23EA06IzP4pxL9MLseqbMMZw+zFRXQlewPPUV5KPNEBbGZCL2RwOZtjrYi+ybkhmhJvTT0T84MgH0bqwfrasnrcFh5TOrqV1XlFiqU= ARC-Authentication-Results:i=1; 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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=io4TU7/DsYQYsJUedIdRHszCi+5jp6aoPhmtlQdzCsDEgUbdY+tFyAgAO5UvP+ufY VaBrlt3u0qA0RHBNBTTsLzP7YUYuG+km+azhHMbaP7Z7J3emWSRVHD6aHwoHSkoGQM lhgQElrAln6e/U6oXeGtJqIxGDZhab4Li0avWXZTHbs97OpAEdLHKH0LCvrWwVS/Sm ZJvZjpdQPSChqv4FrWibkgPwePB8YrX7Dmu/jRH7HbAhqhs3HLXNaliH7zx2ouE7ei ZDUWZxJX0zPu3MlKWBbYvoh/JCnzGDuIRgAgRztFSFtwmkz10M6g+BBeGRDiZJaG0z kwx7S2OPtsLbw== Message-ID: <00358cf3-e59a-4a5f-8cfd-06a174da72b4@zytor.com> Date: Fri, 13 Jun 2025 10:58:34 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/3] x86/traps: Move DR7_RESET_VALUE to To: Sean Christopherson Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, pbonzini@redhat.com, peterz@infradead.org, brgerst@gmail.com, tony.luck@intel.com, fenghuay@nvidia.com References: <20250613070118.3694407-1-xin@zytor.com> <20250613070118.3694407-2-xin@zytor.com> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/13/2025 7:18 AM, Sean Christopherson wrote: > On Fri, Jun 13, 2025, Xin Li (Intel) wrote: >> Move DR7_RESET_VALUE to to prepare to write DR7 >> with DR7_RESET_VALUE at boot time. > > Alternatively, what about dropping DR7_RESET_VALUE, moving KVM's DR6 and DR7 > #defines out of arch/x86/include/asm/kvm_host.h, and then using DR7_FIXED_1? We definitely should do it, I see quite a few architectural definitions are in KVM only headers (the native FRED patches needed to reuse the event types that were previously VMX-specific and moved them out of KVM headers). Because there is an UAPI header, we probably don't want to remove definitions from it? Ofc there is a non-UAPI header we can move into. > > Arguably, that'd be an improvement for 2 of the 3 uses of DR7_RESET_VALUE in SEV > code: > > /* Early non-zero writes to DR7 are not supported */ > if (!data && (val & ~DR7_RESET_VALUE)) > return ES_UNSUPPORTED; > > vs. > > /* Early non-zero writes to DR7 are not supported */ > if (!data && (val & ~DR7_FIXED_1)) > return ES_UNSUPPORTED; > > And in vc_handle_dr7_read(): > > if (data) > *reg = data->dr7; > else > *reg = DR7_RESET_VALUE; > > vs. > > if (data) > *reg = data->dr7; > else > *reg = DR7_FIXED_1; > > In both of those cases, it isn't the RESET value that's interesting, it's that > architecturally bit 10 is fixed to '1'. > > I haven't looked at the kernel code, but I suspect DR6_ACTIVE_LOW, DR6_VOLATILE, > and/or DR6_FIXED_1 could also come in handy. I can find time to take a look after the bug-fixing patches. Thanks! Xin