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Thu, 30 May 2024 09:48:00 -0700 Date: Thu, 30 May 2024 19:47:41 +0300 From: Zhi Wang To: Michael Roth CC: Binbin Wu , Paolo Bonzini , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Brijesh Singh , "Yamahata, Isaku" Subject: Re: [PATCH v15 09/20] KVM: SEV: Add support to handle MSR based Page State Change VMGEXIT Message-ID: <20240530194606.00003f3a.zhiw@nvidia.com> In-Reply-To: References: <20240501085210.2213060-1-michael.roth@amd.com> <20240501085210.2213060-10-michael.roth@amd.com> <84e8460d-f8e7-46d7-a274-90ea7aec2203@linux.intel.com> <7d6a4320-89f5-48ce-95ff-54b00e7e9597@linux.intel.com> Organization: NVIDIA X-Mailer: Claws Mail 4.2.0 (GTK 3.24.38; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH3PEPF00000017:EE_|IA1PR12MB8585:EE_ X-MS-Office365-Filtering-Correlation-Id: c12050d6-8097-4c92-eb3d-08dc80c85228 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230031|1800799015|82310400017|7416005|36860700004|376005; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 May 2024 16:48:23.8589 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: c12050d6-8097-4c92-eb3d-08dc80c85228 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CH3PEPF00000017.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR12MB8585 X-Stat-Signature: kdkpfgmtkmr8rgtc7oxzmrfdpyywxdg6 X-Rspamd-Queue-Id: EB440C0006 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1717087707-999793 X-HE-Meta: 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 SzPtQ0EH s5iGaTntfq3cha2jXXy0tvBQYtbTe6q7eSK13QCXqOBFU/3+w3F2w6RSJWJjEtEfNqtYp6tMHkD0mmPeeeJ/lhCA7IwChFX+b+jelZtnbiGnBMwS8QjSvRyyvsPxJltLB/tsM3zPMJRt+/Q1ElV3IgzbjktVtpISjhvCakQymnX22/VlkFV+eAUBDF7MTMFFnMdBexMH2tRO6ehNHTD7edssgHji7fqEmPVFC4CvEokCbdy/PLYydpL7dgNnl0JAcuO7bPJSBmbRi6qcGeJTOIS9DWqSdmNnU26KXPirJdqPs5QQbYEQnpDWUdfKo5eIyC6z7q97bVHHYj8sNf8DyrGAjSrPVmkbnblX+xs4KbSOHCYs7SFUuRnz9WsS7+/hEQ/9y5Mpn5wkHPVXhw3fmk2q81g== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 21 May 2024 16:49:52 -0500 Michael Roth wrote: > On Tue, May 21, 2024 at 08:49:59AM +0800, Binbin Wu wrote: > >=20 > >=20 > > On 5/17/2024 1:23 AM, Paolo Bonzini wrote: > > > On Thu, May 16, 2024 at 10:29=E2=80=AFAM Binbin Wu > > > wrote: > > > >=20 > > > >=20 > > > > On 5/1/2024 4:51 PM, Michael Roth wrote: > > > > > SEV-SNP VMs can ask the hypervisor to change the page state > > > > > in the RMP table to be private or shared using the Page State > > > > > Change MSR protocol as defined in the GHCB specification. > > > > >=20 > > > > > When using gmem, private/shared memory is allocated through > > > > > separate pools, and KVM relies on userspace issuing a > > > > > KVM_SET_MEMORY_ATTRIBUTES KVM ioctl to tell the KVM MMU > > > > > whether or not a particular GFN should be backed by private > > > > > memory or not. > > > > >=20 > > > > > Forward these page state change requests to userspace so that > > > > > it can issue the expected KVM ioctls. The KVM MMU will handle > > > > > updating the RMP entries when it is ready to map a private > > > > > page into a guest. > > > > >=20 > > > > > Use the existing KVM_HC_MAP_GPA_RANGE hypercall format to > > > > > deliver these requests to userspace via KVM_EXIT_HYPERCALL. > > > > >=20 > > > > > Signed-off-by: Michael Roth > > > > > Co-developed-by: Brijesh Singh > > > > > Signed-off-by: Brijesh Singh > > > > > Signed-off-by: Ashish Kalra > > > > > --- > > > > > arch/x86/include/asm/sev-common.h | 6 ++++ > > > > > arch/x86/kvm/svm/sev.c | 48 > > > > > +++++++++++++++++++++++++++++++ 2 files changed, 54 > > > > > insertions(+) > > > > >=20 > > > > > diff --git a/arch/x86/include/asm/sev-common.h > > > > > b/arch/x86/include/asm/sev-common.h index > > > > > 1006bfffe07a..6d68db812de1 100644 --- > > > > > a/arch/x86/include/asm/sev-common.h +++ > > > > > b/arch/x86/include/asm/sev-common.h @@ -101,11 +101,17 @@ > > > > > enum psc_op { /* GHCBData[11:0] */ > > > > > \ GHCB_MSR_PSC_REQ) > > > > >=20 > > > > > +#define GHCB_MSR_PSC_REQ_TO_GFN(msr) (((msr) & > > > > > GENMASK_ULL(51, 12)) >> 12) +#define > > > > > GHCB_MSR_PSC_REQ_TO_OP(msr) (((msr) & GENMASK_ULL(55, 52)) >> > > > > > 52) + #define GHCB_MSR_PSC_RESP 0x015 > > > > > #define GHCB_MSR_PSC_RESP_VAL(val) \ > > > > > /* GHCBData[63:32] */ \ > > > > > (((u64)(val) & GENMASK_ULL(63, 32)) >> 32) > > > > >=20 > > > > > +/* Set highest bit as a generic error response */ > > > > > +#define GHCB_MSR_PSC_RESP_ERROR (BIT_ULL(63) | > > > > > GHCB_MSR_PSC_RESP) + > > > > > /* GHCB Hypervisor Feature Request/Response */ > > > > > #define GHCB_MSR_HV_FT_REQ 0x080 > > > > > #define GHCB_MSR_HV_FT_RESP 0x081 > > > > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > > > > > index e1ac5af4cb74..720775c9d0b8 100644 > > > > > --- a/arch/x86/kvm/svm/sev.c > > > > > +++ b/arch/x86/kvm/svm/sev.c > > > > > @@ -3461,6 +3461,48 @@ static void set_ghcb_msr(struct > > > > > vcpu_svm *svm, u64 value) svm->vmcb->control.ghcb_gpa =3D value; > > > > > } > > > > >=20 > > > > > +static int snp_complete_psc_msr(struct kvm_vcpu *vcpu) > > > > > +{ > > > > > + struct vcpu_svm *svm =3D to_svm(vcpu); > > > > > + > > > > > + if (vcpu->run->hypercall.ret) > > > > Do we have definition of ret? I didn't find clear documentation > > > > about it. According to the code, 0 means succssful. Is there > > > > any other error codes need to or can be interpreted? > > > They are defined in include/uapi/linux/kvm_para.h > > >=20 > > > #define KVM_ENOSYS 1000 > > > #define KVM_EFAULT EFAULT /* 14 */ > > > #define KVM_EINVAL EINVAL /* 22 */ > > > #define KVM_E2BIG E2BIG /* 7 */ > > > #define KVM_EPERM EPERM /* 1*/ > > > #define KVM_EOPNOTSUPP 95 > > >=20 > > > Linux however does not expect the hypercall to fail for > > > SEV/SEV-ES; and it will terminate the guest if the PSC operation > > > fails for SEV-SNP. So it's best for userspace if the hypercall > > > always succeeds. :) > > Thanks for the info. > >=20 > > For TDX, it wants to restrict the size of memory range for > > conversion in one hypercall to avoid a too long latency. > > Previously, in TDX QEMU patchset v5, the limitation is in userspace > > and=C2=A0 if the size is too big, the status_code will set to > > TDG_VP_VMCALL_RETRY and the failed GPA for guest to retry is > > updated. > > https://lore.kernel.org/all/20240229063726.610065-51-xiaoyao.li@intel.c= om/ > >=20 > > When TDX converts TDVMCALL_MAP_GPA to KVM_HC_MAP_GPA_RANGE, do you > > think which is more reasonable to set the restriction? In KVM (TDX > > specific code) or userspace? > > If userspace is preferred, then the interface needs to=C2=A0 be extended > > to support it. >=20 > With SNP we might get a batch of requests in a single GHCB request, > and potentially each of those requests need to get set out to > userspace as a single KVM_HC_MAP_GPA_RANGE. The subsequent patch here > handles that in a loop by issuing a new KVM_HC_MAP_GPA_RANGE via the > completion handler. So we also sort of need to split large requests > into multiple userspace requests in some cases. >=20 > It seems like TDX should be able to do something similar by limiting > the size of each KVM_HC_MAP_GPA_RANGE to TDX_MAP_GPA_MAX_LEN, and then > returning TDG_VP_VMCALL_RETRY to guest if the original size was > greater than TDX_MAP_GPA_MAX_LEN. But at that point you're > effectively done with the entire request and can return to guest, so > it actually seems a little more straightforward than the SNP case > above. E.g. TDX has a 1:1 mapping between TDG_VP_VMCALL_MAP_GPA and > KVM_HC_MAP_GPA_RANGE events. (And even similar names :)) >=20 > So doesn't seem like there's a good reason to expose any of these > throttling details to userspace, in which case existing > KVM_HC_MAP_GPA_RANGE interface seems like it should be sufficient. >=20 Is there any rough data about the latency of private-shared and shared-private page conversion? Thanks, Zhi.=20 > -Mike >=20 > >=20 > >=20 > > >=20 > > > > For TDX, it may also want to use KVM_HC_MAP_GPA_RANGE hypercall > > > > to userspace via KVM_EXIT_HYPERCALL. > > > Yes, definitely. > > >=20 > > > Paolo > > >=20 > >=20 >=20