Re: [PATCH v8 01/69] arm64: Add ARM64_HAS_NESTED_VIRT cpufeature

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

 



Hi Marc

On 31/01/2023 09:23, Marc Zyngier wrote:
From: Jintack Lim <jintack.lim@xxxxxxxxxx>

Add a new ARM64_HAS_NESTED_VIRT feature to indicate that the
CPU has the ARMv8.3 nested virtualization capability, together
with the 'kvm-arm.mode=nested' command line option.

This will be used to support nested virtualization in KVM.

Reviewed-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Jintack Lim <jintack.lim@xxxxxxxxxx>
Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxx>
[maz: moved the command-line option to kvm-arm.mode]

Should this be separate kvm-arm mode ? Or can this be tied to
is_kernel_in_hyp_mode() ? Given this mode (from my limited
review) doesn't conflict with normal VHE mode (and RME support),
adding this explicit mode could confuse the user.

In case we need a command line to turn the NV mode on/off,
we could always use the id-override and simply leave this out ?

Cheers
Suzuki


Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
---
  .../admin-guide/kernel-parameters.txt         |  7 +++++-
  arch/arm64/include/asm/kvm_host.h             |  5 ++++
  arch/arm64/kernel/cpufeature.c                | 25 +++++++++++++++++++
  arch/arm64/kvm/arm.c                          |  5 ++++
  arch/arm64/tools/cpucaps                      |  1 +
  5 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6cfa6e3996cf..b7b0704e360e 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2553,9 +2553,14 @@
  			protected: nVHE-based mode with support for guests whose
  				   state is kept private from the host.
+ nested: VHE-based mode with support for nested
+				virtualization. Requires at least ARMv8.3
+				hardware.
+
  			Defaults to VHE/nVHE based on hardware support. Setting
  			mode to "protected" will disable kexec and hibernation
-			for the host.
+			for the host. "nested" is experimental and should be
+			used with extreme caution.
kvm-arm.vgic_v3_group0_trap=
  			[KVM,ARM] Trap guest accesses to GICv3 group-0
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index b14a0199eba4..186f1b759763 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -60,9 +60,14 @@
  enum kvm_mode {
  	KVM_MODE_DEFAULT,
  	KVM_MODE_PROTECTED,
+	KVM_MODE_NV,
  	KVM_MODE_NONE,
  };
+#ifdef CONFIG_KVM
  enum kvm_mode kvm_get_mode(void);
+#else
+static inline enum kvm_mode kvm_get_mode(void) { return KVM_MODE_NONE; };
+#endif
DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index a77315b338e6..3fc14ee86239 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1956,6 +1956,20 @@ static void cpu_copy_el2regs(const struct arm64_cpu_capabilities *__unused)
  		write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);
  }
+static bool has_nested_virt_support(const struct arm64_cpu_capabilities *cap,
+				    int scope)
+{
+	if (kvm_get_mode() != KVM_MODE_NV)
+		return false;
+
+	if (!has_cpuid_feature(cap, scope)) {
+		pr_warn("unavailable: %s\n", cap->desc);
+		return false;
+	}
+
+	return true;
+}
+
  #ifdef CONFIG_ARM64_PAN
  static void cpu_enable_pan(const struct arm64_cpu_capabilities *__unused)
  {
@@ -2215,6 +2229,17 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
  		.matches = runs_at_el2,
  		.cpu_enable = cpu_copy_el2regs,
  	},
+	{
+		.desc = "Nested Virtualization Support",
+		.capability = ARM64_HAS_NESTED_VIRT,
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.matches = has_nested_virt_support,
+		.sys_reg = SYS_ID_AA64MMFR2_EL1,
+		.sign = FTR_UNSIGNED,
+		.field_pos = ID_AA64MMFR2_EL1_NV_SHIFT,
+		.field_width = 4,
+		.min_field_value = ID_AA64MMFR2_EL1_NV_IMP,
+	},
  	{
  		.capability = ARM64_HAS_32BIT_EL0_DO_NOT_USE,
  		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 698787ed87e9..4e1943e3aa42 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2325,6 +2325,11 @@ static int __init early_kvm_mode_cfg(char *arg)
  		return 0;
  	}
+ if (strcmp(arg, "nested") == 0 && !WARN_ON(!is_kernel_in_hyp_mode())) {
+		kvm_mode = KVM_MODE_NV;
+		return 0;
+	}
+
  	return -EINVAL;
  }
  early_param("kvm-arm.mode", early_kvm_mode_cfg);
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index dfeb2c51e257..1af77a3657f7 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -31,6 +31,7 @@ HAS_GENERIC_AUTH_IMP_DEF
  HAS_IRQ_PRIO_MASKING
  HAS_LDAPR
  HAS_LSE_ATOMICS
+HAS_NESTED_VIRT
  HAS_NO_FPSIMD
  HAS_NO_HW_PREFETCH
  HAS_PAN




[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