Re: [PATCH v13 23/35] KVM: x86: Add support for "protected VMs" that can utilize private memory

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 11/6/23 12:00, Fuad Tabba wrote:
Hi,


On Fri, Oct 27, 2023 at 7:23 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:

Add a new x86 VM type, KVM_X86_SW_PROTECTED_VM, to serve as a development
and testing vehicle for Confidential (CoCo) VMs, and potentially to even
become a "real" product in the distant future, e.g. a la pKVM.

The private memory support in KVM x86 is aimed at AMD's SEV-SNP and
Intel's TDX, but those technologies are extremely complex (understatement),
difficult to debug, don't support running as nested guests, and require
hardware that's isn't universally accessible.  I.e. relying SEV-SNP or TDX

nit: "that isn't"

Reviewed-by: Fuad Tabba <tabba@xxxxxxxxxx>
Tested-by: Fuad Tabba <tabba@xxxxxxxxxx>

Hi Fuad,

thanks for your reviews and tests of the gmem patches! Can you please continue replying to v14?

Thanks,

Paolo

Cheers,
/fuad

for maintaining guest private memory isn't a realistic option.

At the very least, KVM_X86_SW_PROTECTED_VM will enable a variety of
selftests for guest_memfd and private memory support without requiring
unique hardware.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
  Documentation/virt/kvm/api.rst  | 32 ++++++++++++++++++++++++++++++++
  arch/x86/include/asm/kvm_host.h | 15 +++++++++------
  arch/x86/include/uapi/asm/kvm.h |  3 +++
  arch/x86/kvm/Kconfig            | 12 ++++++++++++
  arch/x86/kvm/mmu/mmu_internal.h |  1 +
  arch/x86/kvm/x86.c              | 16 +++++++++++++++-
  include/uapi/linux/kvm.h        |  1 +
  virt/kvm/Kconfig                |  5 +++++
  8 files changed, 78 insertions(+), 7 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 38dc1fda4f45..00029436ac5b 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -147,10 +147,29 @@ described as 'basic' will be available.
  The new VM has no virtual cpus and no memory.
  You probably want to use 0 as machine type.

+X86:
+^^^^
+
+Supported X86 VM types can be queried via KVM_CAP_VM_TYPES.
+
+S390:
+^^^^^
+
  In order to create user controlled virtual machines on S390, check
  KVM_CAP_S390_UCONTROL and use the flag KVM_VM_S390_UCONTROL as
  privileged user (CAP_SYS_ADMIN).

+MIPS:
+^^^^^
+
+To use hardware assisted virtualization on MIPS (VZ ASE) rather than
+the default trap & emulate implementation (which changes the virtual
+memory layout to fit in user mode), check KVM_CAP_MIPS_VZ and use the
+flag KVM_VM_MIPS_VZ.
+
+ARM64:
+^^^^^^
+
  On arm64, the physical address size for a VM (IPA Size limit) is limited
  to 40bits by default. The limit can be configured if the host supports the
  extension KVM_CAP_ARM_VM_IPA_SIZE. When supported, use
@@ -8650,6 +8669,19 @@ block sizes is exposed in KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES as a
  64-bit bitmap (each bit describing a block size). The default value is
  0, to disable the eager page splitting.

+8.41 KVM_CAP_VM_TYPES
+---------------------
+
+:Capability: KVM_CAP_MEMORY_ATTRIBUTES
+:Architectures: x86
+:Type: system ioctl
+
+This capability returns a bitmap of support VM types.  The 1-setting of bit @n
+means the VM type with value @n is supported.  Possible values of @n are::
+
+  #define KVM_X86_DEFAULT_VM   0
+  #define KVM_X86_SW_PROTECTED_VM      1
+
  9. Known KVM API problems
  =========================

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f9e8d5642069..dff10051e9b6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1244,6 +1244,7 @@ enum kvm_apicv_inhibit {
  };

  struct kvm_arch {
+       unsigned long vm_type;
         unsigned long n_used_mmu_pages;
         unsigned long n_requested_mmu_pages;
         unsigned long n_max_mmu_pages;
@@ -2077,6 +2078,12 @@ void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd);
  void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
                        int tdp_max_root_level, int tdp_huge_page_level);

+#ifdef CONFIG_KVM_PRIVATE_MEM
+#define kvm_arch_has_private_mem(kvm) ((kvm)->arch.vm_type != KVM_X86_DEFAULT_VM)
+#else
+#define kvm_arch_has_private_mem(kvm) false
+#endif
+
  static inline u16 kvm_read_ldt(void)
  {
         u16 ldt;
@@ -2125,14 +2132,10 @@ enum {
  #define HF_SMM_INSIDE_NMI_MASK (1 << 2)

  # define KVM_MAX_NR_ADDRESS_SPACES     2
+/* SMM is currently unsupported for guests with private memory. */
+# define kvm_arch_nr_memslot_as_ids(kvm) (kvm_arch_has_private_mem(kvm) ? 1 : 2)
  # define kvm_arch_vcpu_memslots_id(vcpu) ((vcpu)->arch.hflags & HF_SMM_MASK ? 1 : 0)
  # define kvm_memslots_for_spte_role(kvm, role) __kvm_memslots(kvm, (role).smm)
-
-static inline int kvm_arch_nr_memslot_as_ids(struct kvm *kvm)
-{
-       return KVM_MAX_NR_ADDRESS_SPACES;
-}
-
  #else
  # define kvm_memslots_for_spte_role(kvm, role) __kvm_memslots(kvm, 0)
  #endif
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 1a6a1f987949..a448d0964fc0 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -562,4 +562,7 @@ struct kvm_pmu_event_filter {
  /* x86-specific KVM_EXIT_HYPERCALL flags. */
  #define KVM_EXIT_HYPERCALL_LONG_MODE   BIT(0)

+#define KVM_X86_DEFAULT_VM     0
+#define KVM_X86_SW_PROTECTED_VM        1
+
  #endif /* _ASM_X86_KVM_H */
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 091b74599c22..8452ed0228cb 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -77,6 +77,18 @@ config KVM_WERROR

           If in doubt, say "N".

+config KVM_SW_PROTECTED_VM
+       bool "Enable support for KVM software-protected VMs"
+       depends on EXPERT
+       depends on X86_64
+       select KVM_GENERIC_PRIVATE_MEM
+       help
+         Enable support for KVM software-protected VMs.  Currently "protected"
+         means the VM can be backed with memory provided by
+         KVM_CREATE_GUEST_MEMFD.
+
+         If unsure, say "N".
+
  config KVM_INTEL
         tristate "KVM for Intel (and compatible) processors support"
         depends on KVM && IA32_FEAT_CTL
diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h
index 86c7cb692786..b66a7d47e0e4 100644
--- a/arch/x86/kvm/mmu/mmu_internal.h
+++ b/arch/x86/kvm/mmu/mmu_internal.h
@@ -297,6 +297,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
                 .max_level = KVM_MAX_HUGEPAGE_LEVEL,
                 .req_level = PG_LEVEL_4K,
                 .goal_level = PG_LEVEL_4K,
+               .is_private = kvm_mem_is_private(vcpu->kvm, cr2_or_gpa >> PAGE_SHIFT),
         };
         int r;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c4d17727b199..e3eb608b6692 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4441,6 +4441,13 @@ static int kvm_ioctl_get_supported_hv_cpuid(struct kvm_vcpu *vcpu,
         return 0;
  }

+static bool kvm_is_vm_type_supported(unsigned long type)
+{
+       return type == KVM_X86_DEFAULT_VM ||
+              (type == KVM_X86_SW_PROTECTED_VM &&
+               IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) && tdp_enabled);
+}
+
  int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
  {
         int r = 0;
@@ -4632,6 +4639,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
         case KVM_CAP_X86_NOTIFY_VMEXIT:
                 r = kvm_caps.has_notify_vmexit;
                 break;
+       case KVM_CAP_VM_TYPES:
+               r = BIT(KVM_X86_DEFAULT_VM);
+               if (kvm_is_vm_type_supported(KVM_X86_SW_PROTECTED_VM))
+                       r |= BIT(KVM_X86_SW_PROTECTED_VM);
+               break;
         default:
                 break;
         }
@@ -12314,9 +12326,11 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
         int ret;
         unsigned long flags;

-       if (type)
+       if (!kvm_is_vm_type_supported(type))
                 return -EINVAL;

+       kvm->arch.vm_type = type;
+
         ret = kvm_page_track_init(kvm);
         if (ret)
                 goto out;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 29e9eb51dec9..5b5820d19e71 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1218,6 +1218,7 @@ struct kvm_ppc_resize_hpt {
  #define KVM_CAP_MEMORY_FAULT_INFO 231
  #define KVM_CAP_MEMORY_ATTRIBUTES 232
  #define KVM_CAP_GUEST_MEMFD 233
+#define KVM_CAP_VM_TYPES 234

  #ifdef KVM_CAP_IRQ_ROUTING

diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 08afef022db9..2c964586aa14 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -104,3 +104,8 @@ config KVM_GENERIC_MEMORY_ATTRIBUTES
  config KVM_PRIVATE_MEM
         select XARRAY_MULTI
         bool
+
+config KVM_GENERIC_PRIVATE_MEM
+       select KVM_GENERIC_MEMORY_ATTRIBUTES
+       select KVM_PRIVATE_MEM
+       bool
--
2.42.0.820.g83a721a137-goog







[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]

  Powered by Linux