From f742b90e61bb53b27771f64bdae05db03a6ab1f2 Mon Sep 17 00:00:00 2001 From: Brijesh Singh Date: Thu, 24 Feb 2022 10:55:49 -0600 Subject: x86/mm: Extend cc_attr to include AMD SEV-SNP The CC_ATTR_GUEST_SEV_SNP can be used by the guest to query whether the SNP (Secure Nested Paging) feature is active. Signed-off-by: Brijesh Singh Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220307213356.2797205-10-brijesh.singh@amd.com --- include/linux/cc_platform.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include/linux/cc_platform.h') diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h index efd8205282da..d08dd65b5c43 100644 --- a/include/linux/cc_platform.h +++ b/include/linux/cc_platform.h @@ -72,6 +72,14 @@ enum cc_attr { * Examples include TDX guest & SEV. */ CC_ATTR_GUEST_UNROLL_STRING_IO, + + /** + * @CC_ATTR_SEV_SNP: Guest SNP is active. + * + * The platform/OS is running as a guest/virtual machine and actively + * using AMD SEV-SNP features. + */ + CC_ATTR_GUEST_SEV_SNP, }; #ifdef CONFIG_ARCH_HAS_CC_PLATFORM -- cgit v1.2.3 From bae1a962ac2c5e6be08319ff3f7d6df542584fce Mon Sep 17 00:00:00 2001 From: Kuppuswamy Sathyanarayanan Date: Wed, 6 Apr 2022 02:29:33 +0300 Subject: x86/topology: Disable CPU online/offline control for TDX guests Unlike regular VMs, TDX guests use the firmware hand-off wakeup method to wake up the APs during the boot process. This wakeup model uses a mailbox to communicate with firmware to bring up the APs. As per the design, this mailbox can only be used once for the given AP, which means after the APs are booted, the same mailbox cannot be used to offline/online the given AP. More details about this requirement can be found in Intel TDX Virtual Firmware Design Guide, sec titled "AP initialization in OS" and in sec titled "Hotplug Device". Since the architecture does not support any method of offlining the CPUs, disable CPU hotplug support in the kernel. Since this hotplug disable feature can be re-used by other VM guests, add a new CC attribute CC_ATTR_HOTPLUG_DISABLED and use it to disable the hotplug support. Attempt to offline CPU will fail with -EOPNOTSUPP. Signed-off-by: Kuppuswamy Sathyanarayanan Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Reviewed-by: Andi Kleen Reviewed-by: Tony Luck Reviewed-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20220405232939.73860-25-kirill.shutemov@linux.intel.com --- arch/x86/coco/core.c | 1 + include/linux/cc_platform.h | 10 ++++++++++ kernel/cpu.c | 7 +++++++ 3 files changed, 18 insertions(+) (limited to 'include/linux/cc_platform.h') diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c index df08edc94f9b..70956f9d7c7e 100644 --- a/arch/x86/coco/core.c +++ b/arch/x86/coco/core.c @@ -20,6 +20,7 @@ static bool intel_cc_platform_has(enum cc_attr attr) { switch (attr) { case CC_ATTR_GUEST_UNROLL_STRING_IO: + case CC_ATTR_HOTPLUG_DISABLED: return true; default: return false; diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h index efd8205282da..691494bbaf5a 100644 --- a/include/linux/cc_platform.h +++ b/include/linux/cc_platform.h @@ -72,6 +72,16 @@ enum cc_attr { * Examples include TDX guest & SEV. */ CC_ATTR_GUEST_UNROLL_STRING_IO, + + /** + * @CC_ATTR_HOTPLUG_DISABLED: Hotplug is not supported or disabled. + * + * The platform/OS is running as a guest/virtual machine does not + * support CPU hotplug feature. + * + * Examples include TDX Guest. + */ + CC_ATTR_HOTPLUG_DISABLED, }; #ifdef CONFIG_ARCH_HAS_CC_PLATFORM diff --git a/kernel/cpu.c b/kernel/cpu.c index 5797c2a7a93f..edb8c199f6a3 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -35,6 +35,7 @@ #include #include #include +#include #include #define CREATE_TRACE_POINTS @@ -1186,6 +1187,12 @@ out: static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target) { + /* + * If the platform does not support hotplug, report it explicitly to + * differentiate it from a transient offlining failure. + */ + if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED)) + return -EOPNOTSUPP; if (cpu_hotplug_disabled) return -EBUSY; return _cpu_down(cpu, 0, target); -- cgit v1.2.3