From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
To: "seanjc@google.com" <seanjc@google.com>
Cc: "erdemaktas@google.com" <erdemaktas@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"jmattson@google.com" <jmattson@google.com>,
"Huang, Kai" <kai.huang@intel.com>,
"vkuznets@redhat.com" <vkuznets@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"ckuehl@redhat.com" <ckuehl@redhat.com>,
"joro@8bytes.org" <joro@8bytes.org>,
"x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"bp@alien8.de" <bp@alien8.de>,
"Yamahata, Isaku" <isaku.yamahata@intel.com>,
"isaku.yamahata@gmail.com" <isaku.yamahata@gmail.com>,
"wanpengli@tencent.com" <wanpengli@tencent.com>
Subject: Re: [RFC PATCH v2 41/69] KVM: x86: Add infrastructure for stolen GPA bits
Date: Thu, 5 Aug 2021 18:43:35 +0000 [thread overview]
Message-ID: <7231028edae70dfaeab304d6206d4426b9233f41.camel@intel.com> (raw)
In-Reply-To: <YQwiPNRYHtnMA5AL@google.com>
On Thu, 2021-08-05 at 17:39 +0000, Sean Christopherson wrote:
> On Thu, Aug 05, 2021, Edgecombe, Rick P wrote:
> > On Thu, 2021-08-05 at 16:06 +0000, Sean Christopherson wrote:
> > > On Thu, Aug 05, 2021, Kai Huang wrote:
> > > > And removing 'gfn_stolen_bits' in 'struct kvm_mmu_page' could
> > > > also save
> > > > some memory.
> > >
> > > But I do like saving memory... One potentially bad idea would be
> > > to
> > > unionize gfn and stolen bits by shifting the stolen bits after
> > > they're
> > > extracted from the gpa, e.g.
> > >
> > > union {
> > > gfn_t gfn_and_stolen;
> > > struct {
> > > gfn_t gfn:52;
> > > gfn_t stolen:12;
> > > }
> > > };
> > >
> > > the downsides being that accessing just the gfn would require an
> > > additional
> > > masking operation, and the stolen bits wouldn't align with
> > > reality.
> >
> > It definitely seems like the sp could be packed more efficiently.
>
> Yeah, in general it could be optimized. But for TDP/direct MMUs, we
> don't care
> thaaat much because there are relatively few shadow pages, versus
> indirect MMUs
> with thousands or tens of thousands of shadow pages. Of course,
> indirect MMUs
> are also the most gluttonous due to the unsync_child_bitmap, gfns,
> write flooding
> count, etc...
>
> If we really want to reduce the memory footprint for the common case
> (TDP MMU),
> the crud that's used only by indirect shadow pages could be shoved
> into a
> different struct by abusing the struct layout and and wrapping
> accesses to the
> indirect-only fields with casts/container_of and helpers, e.g.
>
Wow, didn't realize classic MMU was that relegated already. Mostly an
onlooker here, but does TDX actually need classic MMU support? Nice to
have?
> struct kvm_mmu_indirect_page {
> struct kvm_mmu_page this;
>
> gfn_t *gfns;
> unsigned int unsync_children;
> DECLARE_BITMAP(unsync_child_bitmap, 512);
>
> #ifdef CONFIG_X86_32
> /*
> * Used out of the mmu-lock to avoid reading spte values while
> an
> * update is in progress; see the comments in
> __get_spte_lockless().
> */
> int clear_spte_count;
> #endif
>
> /* Number of writes since the last time traversal visited this
> page. */
> atomic_t write_flooding_count;
> }
>
>
> > One other idea is the stolen bits could just be recovered from the
> > role
> > bits with a helper, like how the page fault error code stolen bits
> > encoding version of this works.
>
> As in, a generic "stolen_gfn_bits" in the role instead of a per-
> feature role bit?
> That would avoid the problem of per-feature role bits leading to a
> pile of
> marshalling code, and wouldn't suffer the masking cost when accessing
> ->gfn,
> though I'm not sure that matters much.
Well I was thinking multiple types of aliases, like the pf err code
stuff works, like this:
gfn_t stolen_bits(struct kvm *kvm, struct kvm_mmu_page *sp)
{
gfn_t stolen = 0;
if (sp->role.shared)
stolen |= kvm->arch.gfn_shared_mask;
if (sp->role.other_alias)
stolen |= kvm->arch.gfn_other_mask;
return stolen;
}
But yea, there really only needs to be one. Still bit shifting seems
better.
>
> > If the stolen bits are not fed into the hash calculation though it
> > would change the behavior a bit. Not sure if for better or worse.
> > Also
> > the calculation of hash collisions would need to be aware.
>
> The role is already factored into the collision logic.
I mean how aliases of the same gfn don't necessarily collide and the
collisions counter is only incremented if the gfn/stolen matches, but
not if the role is different.
>
> > FWIW, I kind of like something like Sean's proposal. It's a bit
> > convoluted, but there are more unused bits in the gfn than the
> > role.
>
> And tightly bound, i.e. there can't be more than gfn_t gfn+gfn_stolen
> bits.
>
> > Also they are a little more related.
>
>
next prev parent reply other threads:[~2021-08-05 18:43 UTC|newest]
Thread overview: 175+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-02 22:04 [RFC PATCH v2 00/69] KVM: X86: TDX support isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 01/69] KVM: TDX: introduce config for KVM " isaku.yamahata
2021-07-06 12:33 ` Paolo Bonzini
2021-07-13 17:54 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 02/69] KVM: X86: move kvm_cpu_vmxon() from vmx.c to virtext.h isaku.yamahata
2021-07-06 12:33 ` Paolo Bonzini
2021-07-13 17:49 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 03/69] KVM: X86: move out the definition vmcs_hdr/vmcs from kvm to x86 isaku.yamahata
2021-07-06 12:33 ` Paolo Bonzini
2021-07-13 18:00 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 04/69] KVM: TDX: Add TDX "architectural" error codes isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 05/69] KVM: TDX: Add architectural definitions for structures and values isaku.yamahata
2021-07-31 1:04 ` Erdem Aktas
2021-08-02 13:25 ` Xiaoyao Li
2021-08-04 20:43 ` Erdem Aktas
2021-08-04 23:13 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 06/69] KVM: TDX: add a helper function for kvm to call seamcall isaku.yamahata
2021-07-06 12:57 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 07/69] KVM: TDX: define and export helper functions for KVM TDX support isaku.yamahata
2021-10-09 7:50 ` Wang, Wei W
2021-07-02 22:04 ` [RFC PATCH v2 08/69] KVM: TDX: add trace point before/after TDX SEAMCALLs isaku.yamahata
2021-07-06 13:23 ` Paolo Bonzini
2021-07-13 19:53 ` Sean Christopherson
2021-07-13 19:33 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 09/69] KVM: TDX: Add C wrapper functions for " isaku.yamahata
2021-07-06 13:25 ` Paolo Bonzini
2021-07-13 19:59 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 10/69] KVM: TDX: Print the name of SEAMCALL status code isaku.yamahata
2021-07-06 13:25 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 11/69] KVM: TDX: Introduce pr_seamcall_ex_ret_info() to print more info when SEAMCALL fails isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 12/69] KVM: Export kvm_io_bus_read for use by TDX for PV MMIO isaku.yamahata
2021-07-06 13:26 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 13/69] KVM: Enable hardware before doing arch VM initialization isaku.yamahata
2021-07-06 13:26 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 14/69] KVM: x86: Split core of hypercall emulation to helper function isaku.yamahata
2021-07-06 13:40 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 15/69] KVM: x86: Export kvm_mmio tracepoint for use by TDX for PV MMIO isaku.yamahata
2021-07-06 13:40 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 16/69] KVM: x86/mmu: Zap only leaf SPTEs for deleted/moved memslot by default isaku.yamahata
2021-07-06 13:44 ` Paolo Bonzini
2021-07-13 20:17 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 17/69] KVM: Add infrastructure and macro to mark VM as bugged isaku.yamahata
2021-07-06 13:45 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 18/69] KVM: Export kvm_make_all_cpus_request() for use in marking VMs " isaku.yamahata
2021-07-06 13:47 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 19/69] KVM: x86: Use KVM_BUG/KVM_BUG_ON to handle bugs that are fatal to the VM isaku.yamahata
2021-07-06 13:47 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 20/69] KVM: x86/mmu: Mark VM as bugged if page fault returns RET_PF_INVALID isaku.yamahata
2021-07-06 13:48 ` Paolo Bonzini
2021-07-13 20:28 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 21/69] KVM: Add max_vcpus field in common 'struct kvm' isaku.yamahata
2021-07-06 13:49 ` Paolo Bonzini
2021-07-13 20:35 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 22/69] KVM: x86: Add vm_type to differentiate legacy VMs from protected VMs isaku.yamahata
2021-07-06 13:56 ` Paolo Bonzini
2021-07-06 13:56 ` Paolo Bonzini
2021-07-13 20:39 ` Sean Christopherson
2021-11-11 3:28 ` Xiaoyao Li
2021-11-11 7:28 ` Paolo Bonzini
2021-11-11 8:29 ` Xiaoyao Li
2021-07-02 22:04 ` [RFC PATCH v2 23/69] KVM: x86: Hoist kvm_dirty_regs check out of sync_regs() isaku.yamahata
2021-07-06 13:57 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 24/69] KVM: x86: Introduce "protected guest" concept and block disallowed ioctls isaku.yamahata
2021-07-06 13:59 ` Paolo Bonzini
2021-07-20 22:08 ` Tom Lendacky
2021-11-09 13:37 ` Xiaoyao Li
2021-11-09 17:15 ` Paolo Bonzini
2021-11-10 1:45 ` Xiaoyao Li
2021-07-02 22:04 ` [RFC PATCH v2 25/69] KVM: x86: Add per-VM flag to disable direct IRQ injection isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 26/69] KVM: x86: Add flag to disallow #MC injection / KVM_X86_SETUP_MCE isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 27/69] KVM: x86: Add flag to mark TSC as immutable (for TDX) isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 28/69] KVM: Add per-VM flag to mark read-only memory as unsupported isaku.yamahata
2021-07-06 14:03 ` Paolo Bonzini
2021-07-06 19:04 ` Brijesh Singh
2021-07-02 22:04 ` [RFC PATCH v2 29/69] KVM: Add per-VM flag to disable dirty logging of memslots for TDs isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 30/69] KVM: x86: Add per-VM flag to disable in-kernel I/O APIC and level routes isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 31/69] KVM: x86: add per-VM flags to disable SMI/INIT/SIPI isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 32/69] KVM: x86: Allow host-initiated WRMSR to set X2APIC regardless of CPUID isaku.yamahata
2021-07-06 14:09 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 33/69] KVM: x86: Add kvm_x86_ops .cache_gprs() and .flush_gprs() isaku.yamahata
2021-07-06 14:10 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 34/69] KVM: x86: Add support for vCPU and device-scoped KVM_MEMORY_ENCRYPT_OP isaku.yamahata
2021-07-06 14:12 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 35/69] KVM: x86: Introduce vm_teardown() hook in kvm_arch_vm_destroy() isaku.yamahata
2021-07-06 14:34 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 36/69] KVM: x86: Add a switch_db_regs flag to handle TDX's auto-switched behavior isaku.yamahata
2021-07-06 14:36 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 37/69] KVM: x86: Check for pending APICv interrupt in kvm_vcpu_has_events() isaku.yamahata
2021-07-06 14:50 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 38/69] KVM: x86: Add option to force LAPIC expiration wait isaku.yamahata
2021-07-06 14:35 ` Paolo Bonzini
2021-07-13 20:51 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 39/69] KVM: x86: Add guest_supported_xss placholder isaku.yamahata
2021-07-06 14:41 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 40/69] KVM: Export kvm_is_reserved_pfn() for use by TDX isaku.yamahata
2021-07-06 14:32 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 41/69] KVM: x86: Add infrastructure for stolen GPA bits isaku.yamahata
2021-07-06 14:54 ` Paolo Bonzini
2021-08-05 11:44 ` Kai Huang
2021-08-05 16:06 ` Sean Christopherson
2021-08-05 17:07 ` Edgecombe, Rick P
2021-08-05 17:39 ` Sean Christopherson
2021-08-05 18:43 ` Edgecombe, Rick P [this message]
2021-08-05 18:58 ` Sean Christopherson
2021-08-05 21:59 ` Kai Huang
2021-08-06 19:02 ` Sean Christopherson
2021-08-06 22:00 ` Kai Huang
2021-08-06 22:09 ` Sean Christopherson
2021-08-06 22:24 ` Kai Huang
2021-07-02 22:04 ` [RFC PATCH v2 42/69] KVM: x86/mmu: Explicitly check for MMIO spte in fast page fault isaku.yamahata
2021-07-06 14:54 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 43/69] KVM: x86/mmu: Allow non-zero init value for shadow PTE isaku.yamahata
2021-07-06 14:56 ` Paolo Bonzini
2021-07-08 15:20 ` Isaku Yamahata
2021-07-02 22:04 ` [RFC PATCH v2 44/69] KVM: x86/mmu: Refactor shadow walk in __direct_map() to reduce indentation isaku.yamahata
2021-07-06 14:56 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 45/69] KVM: x86/mmu: Return old SPTE from mmu_spte_clear_track_bits() isaku.yamahata
2021-07-06 14:56 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 46/69] KVM: x86/mmu: Frame in support for private/inaccessible shadow pages isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 47/69] KVM: x86/mmu: Move 'pfn' variable to caller of direct_page_fault() isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 48/69] KVM: x86/mmu: Introduce kvm_mmu_map_tdp_page() for use by TDX isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 49/69] KVM: VMX: Modify NMI and INTR handlers to take intr_info as param isaku.yamahata
2021-07-06 14:50 ` Paolo Bonzini
2021-07-02 22:04 ` [RFC PATCH v2 50/69] KVM: VMX: Move NMI/exception handler to common helper isaku.yamahata
2021-07-02 22:04 ` [RFC PATCH v2 51/69] KVM: x86/mmu: Allow per-VM override of the TDP max page level isaku.yamahata
2021-07-06 14:58 ` Paolo Bonzini
2021-07-13 21:02 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 52/69] KVM: VMX: Split out guts of EPT violation to common/exposed function isaku.yamahata
2021-07-06 14:52 ` Paolo Bonzini
2021-07-13 20:57 ` Sean Christopherson
2021-07-02 22:04 ` [RFC PATCH v2 53/69] KVM: VMX: Define EPT Violation architectural bits isaku.yamahata
2021-07-06 14:41 ` Paolo Bonzini
2021-07-02 22:05 ` [RFC PATCH v2 54/69] KVM: VMX: Define VMCS encodings for shared EPT pointer isaku.yamahata
2021-07-06 14:42 ` Paolo Bonzini
2021-07-02 22:05 ` [RFC PATCH v2 55/69] KVM: VMX: Add 'main.c' to wrap VMX and TDX isaku.yamahata
2021-07-06 14:43 ` Paolo Bonzini
2021-07-08 15:21 ` Isaku Yamahata
2021-07-08 15:29 ` Paolo Bonzini
2021-07-02 22:05 ` [RFC PATCH v2 56/69] KVM: VMX: Move setting of EPT MMU masks to common VT-x code isaku.yamahata
2021-07-06 14:43 ` Paolo Bonzini
2021-07-02 22:05 ` [RFC PATCH v2 57/69] KVM: VMX: Move register caching logic to common code isaku.yamahata
2021-07-06 14:44 ` Paolo Bonzini
2021-07-02 22:05 ` [RFC PATCH v2 58/69] KVM: TDX: Define TDCALL exit reason isaku.yamahata
2021-07-02 22:05 ` [RFC PATCH v2 59/69] KVM: TDX: Stub in tdx.h with structs, accessors, and VMCS helpers isaku.yamahata
2021-07-02 22:05 ` [RFC PATCH v2 60/69] KVM: VMX: Add macro framework to read/write VMCS for VMs and TDs isaku.yamahata
2021-07-06 14:46 ` Paolo Bonzini
2021-07-13 20:56 ` Sean Christopherson
2021-07-02 22:05 ` [RFC PATCH v2 61/69] KVM: VMX: Move AR_BYTES encoder/decoder helpers to common.h isaku.yamahata
2021-07-06 14:46 ` Paolo Bonzini
2021-07-02 22:05 ` [RFC PATCH v2 62/69] KVM: VMX: MOVE GDT and IDT accessors to common code isaku.yamahata
2021-07-06 14:46 ` Paolo Bonzini
2021-07-02 22:05 ` [RFC PATCH v2 63/69] KVM: VMX: Move .get_interrupt_shadow() implementation to common VMX code isaku.yamahata
2021-07-06 14:17 ` Paolo Bonzini
2021-07-13 20:45 ` Sean Christopherson
2021-07-02 22:05 ` [RFC PATCH v2 64/69] cpu/hotplug: Document that TDX also depends on booting CPUs once isaku.yamahata
2021-07-02 22:05 ` [RFC PATCH v2 65/69] KVM: X86: Introduce initial_tsc_khz in struct kvm_arch isaku.yamahata
2021-07-06 14:22 ` Paolo Bonzini
2021-07-13 18:14 ` Sean Christopherson
2021-07-26 5:31 ` Xiaoyao Li
2021-07-13 18:09 ` Sean Christopherson
2021-07-02 22:05 ` [RFC PATCH v2 66/69] KVM: TDX: Add "basic" support for building and running Trust Domains isaku.yamahata
[not found] ` <CAAYXXYyz3S_cc9ohfkUWN4ohrNq5f+h3608CW5twb-n8i=ogBA@mail.gmail.com>
2021-10-21 21:44 ` Sagi Shahar
2021-10-24 12:59 ` Xiaoyao Li
2021-07-02 22:05 ` [RFC PATCH v2 67/69] KVM: TDX: add trace point for TDVMCALL and SEPT operation isaku.yamahata
2021-07-06 14:23 ` Paolo Bonzini
2021-07-02 22:05 ` [RFC PATCH v2 68/69] KVM: TDX: add document on TDX MODULE isaku.yamahata
2021-07-06 14:23 ` Paolo Bonzini
2021-07-02 22:05 ` [RFC PATCH v2 69/69] Documentation/virtual/kvm: Add Trust Domain Extensions(TDX) isaku.yamahata
2021-07-06 14:49 ` [RFC PATCH v2 00/69] KVM: X86: TDX support Paolo Bonzini
2021-07-06 14:53 ` Paolo Bonzini
2021-07-26 12:56 ` Paolo Bonzini
2021-07-28 16:51 ` Sean Christopherson
2021-08-02 7:33 ` Paolo Bonzini
2021-08-02 15:12 ` Sean Christopherson
2021-08-02 15:46 ` Paolo Bonzini
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