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Date:   Thu, 12 Jan 2023 08:32:46 -0600
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Subject: Re: [PATCH kernel v2 2/3] KVM: SEV: Enable data breakpoints in SEV-ES
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To:     Borislav Petkov <bp@alien8.de>, Alexey Kardashevskiy <aik@amd.com>
Cc:     kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org,
        Venu Busireddy <venu.busireddy@oracle.com>,
        Tony Luck <tony.luck@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Sean Christopherson <seanjc@google.com>,
        Sandipan Das <sandipan.das@amd.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Michael Roth <michael.roth@amd.com>,
        Mario Limonciello <mario.limonciello@amd.com>,
        Jan Kara <jack@suse.cz>, Ingo Molnar <mingo@redhat.com>,
        Huang Rui <ray.huang@amd.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Daniel Sneddon <daniel.sneddon@linux.intel.com>,
        Brijesh Singh <brijesh.singh@amd.com>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Andrew Cooper <andrew.cooper3@citrix.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>,
        "H. Peter Anvin" <hpa@zytor.com>
References: <20221209043804.942352-1-aik@amd.com>
 <20221209043804.942352-3-aik@amd.com> <Y72nyuKT+VJYiEUi@zn.tnic>
 <f18c83ac-dc9a-6173-7ab3-d5e3718a0047@amd.com> <Y7/u76mREet2IrtQ@zn.tnic>
From:   Tom Lendacky <thomas.lendacky@amd.com>
In-Reply-To: <Y7/u76mREet2IrtQ@zn.tnic>
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On 1/12/23 05:28, Borislav Petkov wrote:
> On Thu, Jan 12, 2023 at 04:45:34PM +1100, Alexey Kardashevskiy wrote:
>> Well, SEV-ES KVM (ES == Encrypted State) does not save/restore them for the
>> guest (well, as I would expect) as the guest registers are not visible to
>> host to save, they are intercepted and the VM does this GHCB dance with
>> VMGEXIT(SVM_EXIT_WRITE_DR7).
> 
> But they're saved in the VMSA, as Table B-3 says.

Correct, when this feature is enabled, the VMRUN execution will restore 
the guest debug registers on guest entry and save them on guest exit.

Thanks,
Tom

> 
>> Well, the only place in APM is that "Table B-3. Swap Types and the AMD APM
>> volume 2", and it is pretty brief, do I miss something?
> 
> I don't understand that question - please elaborate.
> 
> Thx.
>