From: Sean Christopherson <seanjc@google.com>
To: Brijesh Singh <brijesh.singh@amd.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
kvm@vger.kernel.org, linux-efi@vger.kernel.org,
platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev,
linux-mm@kvack.org, linux-crypto@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
Tom Lendacky <thomas.lendacky@amd.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Ard Biesheuvel <ardb@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Andy Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Dov Murik <dovmurik@linux.ibm.com>,
Tobin Feldman-Fitzthum <tobin@ibm.com>,
Borislav Petkov <bp@alien8.de>,
Michael Roth <michael.roth@amd.com>,
Vlastimil Babka <vbabka@suse.cz>,
tony.luck@intel.com, npmccallum@redhat.com,
brijesh.ksingh@gmail.com
Subject: Re: [PATCH Part2 RFC v4 25/40] KVM: SVM: Reclaim the guest pages when SEV-SNP VM terminates
Date: Sat, 17 Jul 2021 00:46:34 +0000 [thread overview]
Message-ID: <YPIoaoDCjNVzn2ZM@google.com> (raw)
In-Reply-To: <2711d9f9-21a0-7baa-d0ff-2c0f69ca6949@amd.com>
On Fri, Jul 16, 2021, Brijesh Singh wrote:
>
> On 7/16/21 3:09 PM, Sean Christopherson wrote:
> > On Wed, Jul 07, 2021, Brijesh Singh wrote:
> >> + e = snp_lookup_page_in_rmptable(region->pages[i], &level);
> >> + if (unlikely(!e))
> >> + continue;
> >> +
> >> + /* If its not a guest assigned page then skip it. */
> >> + if (!rmpentry_assigned(e))
> >> + continue;
> >> +
> >> + /* Is the page part of a 2MB RMP entry? */
> >> + if (level == PG_LEVEL_2M) {
> >> + val.pagesize = RMP_PG_SIZE_2M;
> >> + pfn &= ~(KVM_PAGES_PER_HPAGE(PG_LEVEL_2M) - 1);
> >> + } else {
> >> + val.pagesize = RMP_PG_SIZE_4K;
> > This raises yet more questions (for me) as to the interaction between Page-Size
> > and Hyperivsor-Owned flags in the RMP. It also raises questions on the correctness
> > of zeroing the RMP entry if KVM_SEV_SNP_LAUNCH_START (in the previous patch).
>
> I assume you mean the LAUNCH_UPDATE because that's when we need to
> perform the RMPUPDATE.
Doh, yes.
> The hypervisor owned means all zero in the RMP entry.
Figured out where I went wrong after reading the RMPUDPATE pseudocode. RMPUPDATE
takes the page size as a parameter even though it unconditionally zeros the page
size flag in the RMP entry for unassigned pages.
A wrapper around rmpupdate() would definitely help, e.g. (though level might need
to be an "int" to avoid a bunch of casts).
int rmp_make_shared(u64 pfn, enum pg_level level);
Wrappers for "private" and "firmware" would probably be helpful too. And if you
do that, I think you can bury both "struct rmpupdate", rmpupdate(), and
X86_TO_RMP_PG_LEVEL() in arch/x86/kernel/sev.c. snp_set_rmptable_state() might
need some refactoring to avoid three booleans, but I guess maybe that could be
an exception? Not sure. Anyways, was thinking something like:
int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid);
int rmp_make_firmware(u64 pfn);
It would consolidate a bit of code, and more importantly it would give visual
cues to the reader, e.g. it's easy to overlook "val = {0}" meaning "make shared".
Side topic, what happens if a firmware entry is configured with page_size=1?
And one architectural question: what prevents a malicious VMM from punching a 4k
shared page into a 2mb private page? E.g.
rmpupdate(1 << 20, [private, 2mb]);
rmpupdate(1 << 20 + 4096, [shared, 4kb]);
I don't see any checks in the pseudocode that will detect this, and presumably the
whole point of a 2mb private RMP entry is to not have to go walk the individual
4kb entries on a private access.
NEW_RMP = READ_MEM.o [NEW_RMP_PTR]
IF ((NEW_RMP.PAGE_SIZE == 2MB) && (SYSTEM_PA[20:12] != 0)) <-- not taken, 4kb entry
EAX = FAIL_INPUT
EXIT
IF (!NEW_RMP.ASSIGNED && (NEW_RMP.IMMUTABLE || (NEW_RMP.ASID != 0)) <-- not taken, new entry valid
EAX = FAIL_INPUT
EXIT
RMP_ENTRY_PA = RMP_BASE + 0x4000 + (SYSTEM_PA / 0x1000) * 16
IF (RMP_ENTRY_PA > RMP_END)
EAX = FAIL_INPUT
EXIT
// System address must have an RMP entry
OLD_RMP = READ_MEM_PA.o [RMP_ENTRY_PA]
IF (OLD_RMP.IMMUTABLE) <-- passes, private entry not immutable
EAX = FAIL_PERMISSION
EXIT
IF (NEW_RMP.PAGE_SIZE == 4KB)
IF ((SYSTEM_PA[20:12] == 0) && (OLD_RMP.PAGE_SIZE == 2MB)) <- not taken, PA[12] == 1
EAX = FAIL_OVERLAP
EXIT
ELSE
IF (Any 4KB RMP entry with (RMP.ASSIGNED == 1) exists in 2MB region)
EAX = FAIL_OVERLAP
EXIT
ELSE
FOR (I = 1; I < 512, I++) {
temp_RMP = 0
temp_RMP.ASSIGNED = NEW_RMP.ASSIGNED
WRITE_MEM.o [RMP_ENTRY_PA + I * 16] = temp_RMP;
}
next prev parent reply other threads:[~2021-07-17 0:46 UTC|newest]
Thread overview: 178+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-07 18:35 [PATCH Part2 RFC v4 00/40] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 01/40] KVM: SVM: Add support to handle AP reset MSR protocol Brijesh Singh
2021-07-14 20:17 ` Sean Christopherson
2021-07-15 7:39 ` Joerg Roedel
2021-07-15 13:42 ` Tom Lendacky
2021-07-15 15:45 ` Sean Christopherson
2021-07-15 17:05 ` Tom Lendacky
2021-07-07 18:35 ` [PATCH Part2 RFC v4 02/40] KVM: SVM: Provide the Hypervisor Feature support VMGEXIT Brijesh Singh
2021-07-14 20:37 ` Sean Christopherson
2021-07-14 21:00 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 03/40] x86/cpufeatures: Add SEV-SNP CPU feature Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 04/40] x86/sev: Add the host SEV-SNP initialization support Brijesh Singh
2021-07-14 21:07 ` Sean Christopherson
2021-07-14 22:02 ` Brijesh Singh
2021-07-14 22:06 ` Sean Christopherson
2021-07-14 22:11 ` Brijesh Singh
2022-06-02 11:47 ` Jarkko Sakkinen
2022-06-06 11:42 ` Dr. David Alan Gilbert
2021-07-07 18:35 ` [PATCH Part2 RFC v4 05/40] x86/sev: Add RMP entry lookup helpers Brijesh Singh
2021-07-15 18:37 ` Sean Christopherson
2021-07-15 19:28 ` Brijesh Singh
2021-07-16 17:22 ` Brijesh Singh
2021-07-20 22:06 ` Sean Christopherson
2021-07-20 23:10 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 06/40] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction Brijesh Singh
2021-07-12 18:44 ` Peter Gonda
2021-07-12 19:00 ` Dave Hansen
2021-07-15 18:56 ` Sean Christopherson
2021-07-15 19:08 ` Dave Hansen
2021-07-15 19:18 ` Sean Christopherson
2021-07-07 18:35 ` [PATCH Part2 RFC v4 07/40] x86/sev: Split the physmap when adding the page in RMP table Brijesh Singh
2021-07-14 22:25 ` Sean Christopherson
2021-07-15 17:05 ` Brijesh Singh
2021-07-15 17:51 ` Sean Christopherson
2021-07-15 18:14 ` Brijesh Singh
2021-07-15 18:39 ` Sean Christopherson
2021-07-15 19:38 ` Brijesh Singh
2021-07-15 22:01 ` Sean Christopherson
2021-07-15 22:11 ` Brijesh Singh
2021-07-30 11:31 ` Vlastimil Babka
2021-07-30 16:10 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 08/40] x86/traps: Define RMP violation #PF error code Brijesh Singh
2021-07-15 19:02 ` Sean Christopherson
2021-07-15 19:16 ` Dave Hansen
2021-07-07 18:35 ` [PATCH Part2 RFC v4 09/40] x86/fault: Add support to dump RMP entry on fault Brijesh Singh
2021-07-07 19:21 ` Dave Hansen
2021-07-08 15:02 ` Brijesh Singh
2021-07-08 15:30 ` Dave Hansen
2021-07-08 16:48 ` Brijesh Singh
2021-07-08 16:58 ` Dave Hansen
2021-07-08 17:11 ` Brijesh Singh
2021-07-08 17:15 ` Dave Hansen
2021-07-07 18:35 ` [PATCH Part2 RFC v4 10/40] x86/fault: Add support to handle the RMP fault for user address Brijesh Singh
2021-07-08 16:16 ` Dave Hansen
2021-07-12 15:43 ` Brijesh Singh
2021-07-12 16:00 ` Dave Hansen
2021-07-12 16:11 ` Brijesh Singh
2021-07-12 16:15 ` Dave Hansen
2021-07-12 16:24 ` Brijesh Singh
2021-07-12 16:29 ` Dave Hansen
2021-07-12 16:49 ` Brijesh Singh
2021-07-15 21:53 ` Sean Christopherson
2021-07-30 16:00 ` Vlastimil Babka
2021-07-30 16:31 ` Dave Hansen
2021-07-07 18:35 ` [PATCH Part2 RFC v4 11/40] crypto:ccp: Define the SEV-SNP commands Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 12/40] crypto: ccp: Add support to initialize the AMD-SP for SEV-SNP Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 13/40] crypto: ccp: Shutdown SNP firmware on kexec Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 14/40] crypto:ccp: Provide APIs to issue SEV-SNP commands Brijesh Singh
2021-07-08 18:56 ` Dr. David Alan Gilbert
2021-07-07 18:35 ` [PATCH Part2 RFC v4 15/40] crypto: ccp: Handle the legacy TMR allocation when SNP is enabled Brijesh Singh
2021-07-14 13:22 ` Marc Orr
2021-07-14 16:45 ` Brijesh Singh
2021-07-14 18:14 ` Marc Orr
2021-07-15 23:48 ` Sean Christopherson
2021-07-16 12:55 ` Brijesh Singh
2021-07-16 15:35 ` Sean Christopherson
2021-07-16 15:47 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 16/40] crypto: ccp: Handle the legacy SEV command " Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 17/40] crypto: ccp: Add the SNP_PLATFORM_STATUS command Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 18/40] crypto: ccp: Add the SNP_{SET,GET}_EXT_CONFIG command Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 19/40] crypto: ccp: provide APIs to query extended attestation report Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 20/40] KVM: SVM: Make AVIC backing, VMSA and VMCB memory allocation SNP safe Brijesh Singh
2021-07-14 13:35 ` Marc Orr
2021-07-14 16:47 ` Brijesh Singh
2021-07-20 18:02 ` Sean Christopherson
2021-08-03 14:38 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 21/40] KVM: SVM: Add initial SEV-SNP support Brijesh Singh
2021-07-16 18:00 ` Sean Christopherson
2021-07-16 18:46 ` Brijesh Singh
2021-07-16 19:31 ` Sean Christopherson
2021-07-16 21:03 ` Brijesh Singh
2021-07-07 18:35 ` [PATCH Part2 RFC v4 22/40] KVM: SVM: Add KVM_SNP_INIT command Brijesh Singh
2021-07-16 19:33 ` Sean Christopherson
2021-07-16 21:25 ` Brijesh Singh
2021-07-19 20:24 ` Sean Christopherson
2021-07-07 18:35 ` [PATCH Part2 RFC v4 23/40] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_START command Brijesh Singh
2021-07-12 18:45 ` Peter Gonda
2021-07-16 19:43 ` Sean Christopherson
2021-07-16 21:42 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 24/40] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_UPDATE command Brijesh Singh
2021-07-16 20:01 ` Sean Christopherson
2021-07-16 22:00 ` Brijesh Singh
2021-07-19 20:51 ` Sean Christopherson
2021-07-19 21:34 ` Brijesh Singh
2021-07-19 21:36 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 25/40] KVM: SVM: Reclaim the guest pages when SEV-SNP VM terminates Brijesh Singh
2021-07-16 20:09 ` Sean Christopherson
2021-07-16 22:16 ` Brijesh Singh
2021-07-17 0:46 ` Sean Christopherson [this message]
2021-07-19 12:55 ` Brijesh Singh
2021-07-19 17:18 ` Sean Christopherson
2021-07-19 18:34 ` Brijesh Singh
2021-07-19 19:03 ` Sean Christopherson
2021-07-19 19:14 ` Sean Christopherson
2021-07-19 19:37 ` Brijesh Singh
2021-07-20 16:40 ` Sean Christopherson
2021-07-20 18:23 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 26/40] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command Brijesh Singh
2021-07-16 20:18 ` Sean Christopherson
2021-07-16 22:48 ` Brijesh Singh
2021-07-19 16:54 ` Sean Christopherson
2021-07-19 18:29 ` Brijesh Singh
2021-07-19 19:14 ` Sean Christopherson
2021-07-19 19:49 ` Brijesh Singh
2021-07-19 20:13 ` Sean Christopherson
2021-07-21 17:53 ` Marc Orr
2021-07-07 18:36 ` [PATCH Part2 RFC v4 27/40] KVM: X86: Add kvm_x86_ops to get the max page level for the TDP Brijesh Singh
2021-07-16 19:19 ` Sean Christopherson
2021-07-16 20:41 ` Brijesh Singh
2021-07-20 19:38 ` Sean Christopherson
2021-07-20 20:06 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 28/40] KVM: X86: Introduce kvm_mmu_map_tdp_page() for use by SEV Brijesh Singh
2021-07-16 18:15 ` Sean Christopherson
2021-07-07 18:36 ` [PATCH Part2 RFC v4 29/40] KVM: X86: Introduce kvm_mmu_get_tdp_walk() for SEV-SNP use Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 30/40] KVM: X86: Define new RMP check related #NPF error bits Brijesh Singh
2021-07-16 20:22 ` Sean Christopherson
2021-07-17 0:34 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 31/40] KVM: X86: update page-fault trace to log the 64-bit error code Brijesh Singh
2021-07-16 20:25 ` Sean Christopherson
2021-07-17 0:35 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 32/40] KVM: SVM: Add support to handle GHCB GPA register VMGEXIT Brijesh Singh
2021-07-16 20:45 ` Sean Christopherson
2021-07-17 0:44 ` Brijesh Singh
2021-07-19 20:04 ` Sean Christopherson
2021-07-07 18:36 ` [PATCH Part2 RFC v4 33/40] KVM: SVM: Add support to handle MSR based Page State Change VMGEXIT Brijesh Singh
2021-07-16 21:00 ` Sean Christopherson
2021-07-19 14:19 ` Brijesh Singh
2021-07-19 18:55 ` Sean Christopherson
2021-07-19 19:15 ` Brijesh Singh
2021-08-13 16:32 ` Borislav Petkov
2021-07-07 18:36 ` [PATCH Part2 RFC v4 34/40] KVM: SVM: Add support to handle " Brijesh Singh
2021-07-16 21:14 ` Sean Christopherson
2021-07-19 14:24 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 35/40] KVM: Add arch hooks to track the host write to guest memory Brijesh Singh
2021-07-19 23:30 ` Sean Christopherson
2021-07-20 15:15 ` Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 36/40] KVM: X86: Export the kvm_zap_gfn_range() for the SNP use Brijesh Singh
2021-07-07 18:36 ` [PATCH Part2 RFC v4 37/40] KVM: SVM: Add support to handle the RMP nested page fault Brijesh Singh
2021-07-20 0:10 ` Sean Christopherson
2021-07-20 17:55 ` Brijesh Singh
2021-07-20 22:31 ` Sean Christopherson
2021-07-20 23:53 ` Brijesh Singh
2021-07-21 20:15 ` Sean Christopherson
2021-07-07 18:36 ` [PATCH Part2 RFC v4 38/40] KVM: SVM: Provide support for SNP_GUEST_REQUEST NAE event Brijesh Singh
2021-07-19 22:50 ` Sean Christopherson
2021-07-20 14:37 ` Brijesh Singh
2021-07-20 16:28 ` Sean Christopherson
2021-07-20 18:21 ` Brijesh Singh
2021-07-20 22:09 ` Sean Christopherson
2021-07-07 18:36 ` [PATCH Part2 RFC v4 39/40] KVM: SVM: Use a VMSA physical address variable for populating VMCB Brijesh Singh
2021-07-21 0:20 ` Sean Christopherson
2021-07-21 16:26 ` Tom Lendacky
2021-07-07 18:36 ` [PATCH Part2 RFC v4 40/40] KVM: SVM: Support SEV-SNP AP Creation NAE event Brijesh Singh
2021-07-21 0:01 ` Sean Christopherson
2021-07-21 17:47 ` Tom Lendacky
2021-07-21 19:52 ` Sean Christopherson
2021-08-20 14:44 ` Tom Lendacky
2021-07-08 15:40 ` [PATCH Part2 RFC v4 00/40] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Dave Hansen
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