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From: Brijesh Singh <brijesh.singh@amd.com>
To: Sean Christopherson <seanjc@google.com>
Cc: brijesh.singh@amd.com, 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 07/40] x86/sev: Split the physmap when adding the page in RMP table
Date: Thu, 15 Jul 2021 17:11:35 -0500	[thread overview]
Message-ID: <c4b137b5-76f7-fe92-cfe0-d0f7ec72cc36@amd.com> (raw)
In-Reply-To: <YPCwPd2OzbBPs9DH@google.com>


On 7/15/21 5:01 PM, Sean Christopherson wrote:
> On Thu, Jul 15, 2021, Brijesh Singh wrote:
>>
>> On 7/15/21 1:39 PM, Sean Christopherson wrote:
>>> On Thu, Jul 15, 2021, Brijesh Singh wrote:
>>>> The memfd_secrets uses the set_direct_map_{invalid,default}_noflush() and it
>>>> is designed to remove/add the present bit in the direct map. We can't use
>>>> them, because in our case the page may get accessed by the KVM (e.g
>>>> kvm_guest_write, kvm_guest_map etc).
>>> But KVM should never access a guest private page, i.e. the direct map should
>>> always be restored to PRESENT before KVM attempts to access the page.
>>>
>> Yes, KVM should *never* access the guest private pages. So, we could
>> potentially enhance the RMPUPDATE() to check for the assigned and act
>> accordingly.
>>
>> Are you thinking something along the line of this:
>>
>> int rmpupdate(struct page *page, struct rmpupdate *val)
>> {
>> 	...
>> 	
>> 	/*
>> 	 * If page is getting assigned in the RMP entry then unmap
>> 	 * it from the direct map before its added in the RMP table.
>> 	 */
>> 	if (val.assigned)
>> 		set_direct_map_invalid_noflush(page_to_virt(page), 1);
>>
>> 	...
>>
>> 	/*
>> 	 * If the page is getting unassigned then restore the mapping
>> 	 * in the direct map after its removed from the RMP table.
>> 	 */
>> 	if (!val.assigned)
>> 		set_direct_map_default_noflush(page_to_virt(page), 1);
>> 	
>> 	...
>> }
> Yep.
>
> However, looking at the KVM usage, rmpupdate() appears to be broken.  When
> handling a page state change, the guest can specify a 2mb page.  In that case,
> rmpupdate() will be called once for a 2mb page, but this flow assumes a single
> 4kb page.  The current code works because set_memory_4k() will cause the entire
> 2mb page to be shattered, but it's technically wrong and switching to the above
> would cause problems.


Yep, this was just an example to make sure I am able to follow you
correctly. In the actual patch I am going to read the pagesize from the
RMPUPDATE structure and  calculated npages for the
set_direct_map_default(...). As you said it was not needed in the case
of set_memory_4k() because the function force splits the large page.
Whereas with set_direct_map_default(), it first checks whether the split
is required, if not, then skip and update the attributes.

-Brijesh


  reply	other threads:[~2021-07-15 22:11 UTC|newest]

Thread overview: 176+ 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
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 [this message]
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
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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