Author: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date: Mon Mar 11 12:29:43 2024 -0700
Documentation/hw-vuln: Add documentation for RFDS
commit 4e42765d1be01111df0c0275bbaf1db1acef346e upstream.
Add the documentation for transient execution vulnerability Register
File Data Sampling (RFDS) that affects Intel Atom CPUs.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Author: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date: Mon Mar 11 12:29:43 2024 -0700
KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests
commit 2a0180129d726a4b953232175857d442651b55a0 upstream.
Mitigation for RFDS requires RFDS_CLEAR capability which is enumerated
by MSR_IA32_ARCH_CAPABILITIES bit 27. If the host has it set, export it
to guests so that they can deploy the mitigation.
RFDS_NO indicates that the system is not vulnerable to RFDS, export it
to guests so that they don't deploy the mitigation unnecessarily. When
the host is not affected by X86_BUG_RFDS, but has RFDS_NO=0, synthesize
RFDS_NO to the guest.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Author: Sasha Levin <sashal@kernel.org>
Date: Wed Mar 13 07:41:34 2024 -0400
Linux 6.8.1
Tested-by: Bagas Sanjaya <bagasdotme@gmail.com>
Tested-by: Luna Jernberg <droidbittin@gmail.com>
Tested-by: Ron Economos <re@w6rz.net>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Florian Fainelli <florian.fainelli@broadcom.com>
Tested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Author: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date: Mon Mar 11 12:29:43 2024 -0700
x86/mmio: Disable KVM mitigation when X86_FEATURE_CLEAR_CPU_BUF is set
commit e95df4ec0c0c9791941f112db699fae794b9862a upstream.
Currently MMIO Stale Data mitigation for CPUs not affected by MDS/TAA is
to only deploy VERW at VMentry by enabling mmio_stale_data_clear static
branch. No mitigation is needed for kernel->user transitions. If such
CPUs are also affected by RFDS, its mitigation may set
X86_FEATURE_CLEAR_CPU_BUF to deploy VERW at kernel->user and VMentry.
This could result in duplicate VERW at VMentry.
Fix this by disabling mmio_stale_data_clear static branch when
X86_FEATURE_CLEAR_CPU_BUF is enabled.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Author: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date: Mon Mar 11 12:29:43 2024 -0700
x86/rfds: Mitigate Register File Data Sampling (RFDS)
commit 8076fcde016c9c0e0660543e67bff86cb48a7c9c upstream.
RFDS is a CPU vulnerability that may allow userspace to infer kernel
stale data previously used in floating point registers, vector registers
and integer registers. RFDS only affects certain Intel Atom processors.
Intel released a microcode update that uses VERW instruction to clear
the affected CPU buffers. Unlike MDS, none of the affected cores support
SMT.
Add RFDS bug infrastructure and enable the VERW based mitigation by
default, that clears the affected buffers just before exiting to
userspace. Also add sysfs reporting and cmdline parameter
"reg_file_data_sampling" to control the mitigation.
For details see:
Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>