Pawan Gupta 59d665a709 KVM: x86/speculation: Disable Fill buffer clear within guests ... commit 027bbb884b upstream The enumeration of MD_CLEAR in CPUID(EAX=7,ECX=0).EDX{bit 10} is not an accurate indicator on all CPUs of whether the VERW instruction will overwrite fill buffers. FB_CLEAR enumeration in IA32_ARCH_CAPABILITIES{bit 17} covers the case of CPUs that are not vulnerable to MDS/TAA, indicating that microcode does overwrite fill buffers. Guests running in VMM environments may not be aware of all the capabilities/vulnerabilities of the host CPU. Specifically, a guest may apply MDS/TAA mitigations when a virtual CPU is enumerated as vulnerable to MDS/TAA even when the physical CPU is not. On CPUs that enumerate FB_CLEAR_CTRL the VMM may set FB_CLEAR_DIS to skip overwriting of fill buffers by the VERW instruction. This is done by setting FB_CLEAR_DIS during VMENTER and resetting on VMEXIT. For guests that enumerate FB_CLEAR (explicitly asking for fill buffer clear capability) the VMM will not use FB_CLEAR_DIS. Irrespective of guest state, host overwrites CPU buffers before VMENTER to protect itself from an MMIO capable guest, as part of mitigation for MMIO Stale Data vulnerabilities. Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-06-16 13:30:34 +02:00
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alpha/include	tools headers uapi: Sync asm-generic/mman-common.h and linux/mman.h	2019-03-28 14:31:56 -03:00
arc/include/uapi/asm	tools arch uapi: Copy missing unistd.h headers for arc, hexagon and riscv	2019-05-02 16:00:20 -04:00
arm/include	tools headers kvm: Sync kvm headers with the kernel sources	2019-12-02 12:54:13 -03:00
arm64/include	tools headers UAPI: Sync files changed by the memfd_secret new syscall	2021-07-14 10:05:35 -03:00
csky/include/uapi/asm	csky: Add support for libdw	2019-05-15 16:36:46 -03:00
h8300/include
hexagon/include/uapi/asm	tools arch uapi: Copy missing unistd.h headers for arc, hexagon and riscv	2019-05-02 16:00:20 -04:00
ia64/include	ia64: tools: remove duplicate definition of ia64_mf() on ia64	2021-04-16 16:10:37 -07:00
microblaze/include/uapi/asm
mips/include	perf tools: Copy uapi/asm/perf_regs.h from the kernel for MIPS	2021-06-01 10:07:46 -03:00
parisc/include/uapi/asm	parisc: Add MAP_UNINITIALIZED define	2020-10-15 08:10:39 +02:00
powerpc/include	tools include UAPI powerpc: Sync errno.h with the kernel headers	2021-05-10 09:01:00 -03:00
riscv/include/uapi/asm	Replace HTTP links with HTTPS ones: RISC-V	2020-07-30 11:37:40 -07:00
s390/include	tools headers UAPI s390: Sync ptrace.h kernel headers	2021-03-06 16:54:23 -03:00
sh/include	sh: remove sh5 support	2020-06-01 14:48:52 -04:00
sparc/include	tools headers UAPI: Update tools's copy of mman.h headers	2019-07-29 09:02:58 -03:00
x86	KVM: x86/speculation: Disable Fill buffer clear within guests	2022-06-16 13:30:34 +02:00
xtensa/include	tools headers uapi: Sync asm-generic/mman-common.h and linux/mman.h	2019-03-28 14:31:56 -03:00