linux-kernel - Re: [PATCH Part2 RFC v4 25/40] KVM: SVM: Reclaim the guest pages when SEV-SNP VM terminates

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Message-ID: <912c929c-06ba-a391-36bb-050384907d81@amd.com>
Date:   Mon, 19 Jul 2021 13:34:54 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>, tony.luck@...el.com,
        npmccallum@...hat.com, brijesh.ksingh@...il.com
Subject: Re: [PATCH Part2 RFC v4 25/40] KVM: SVM: Reclaim the guest pages when
 SEV-SNP VM terminates



On 7/19/21 12:18 PM, Sean Christopherson wrote:
>>
>> Okay, I will add helper to make things easier. One case where we will
>> need to directly call the rmpupdate() is during the LAUNCH_UPDATE
>> command. In that case the page is private and its immutable bit is also
>> set. This is because the firmware makes change to the page, and we are
>> required to set the immutable bit before the call.
> 
> Or do "int rmp_make_firmware(u64 pfn, bool immutable)"?
> 

That's not what we need.

We need 'rmp_make_private() + immutable' all in one RMPUPDATE.  Here is 
the snippet from SNP_LAUNCH_UPDATE.


+	/* Transition the page state to pre-guest */
+	memset(&e, 0, sizeof(e));
+	e.assigned = 1;
+	e.gpa = gpa;
+	e.asid = sev_get_asid(kvm);
+	e.immutable = true;
+	e.pagesize = X86_TO_RMP_PG_LEVEL(level);
+	ret = rmpupdate(inpages[i], &e);

thanks