v2: - Dropped already backported patch "x86/bugs: Add asm helpers for executing VERW" https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.6.20&id=48985d64c4c8105aa3497219df063e1489792e59 - Booted fine with KASLR and KPTI enabled. - Rebased to v6.6.20 v1: https://lore.kernel.org/r/20240226-delay-verw-backport-6-6-y-v1-0-aa17b2922725@xxxxxxxxxxxxxxx This is the backport of recently upstreamed series that moves VERW execution to a later point in exit-to-user path. This is needed because in some cases it may be possible for data accessed after VERW executions may end into MDS affected CPU buffers. Moving VERW closer to ring transition reduces the attack surface. Patch 1/6 includes a minor fix that is queued for upstream: https://lore.kernel.org/lkml/170899674562.398.6398007479766564897.tip-bot2@tip-bot2/ Patch 2/6 needed a conflict to be resolved for the hunk swapgs_restore_regs_and_return_to_usermode. This is only compile and boot tested on qemu. Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> To: stable@xxxxxxxxxxxxxxx Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx> --- Pawan Gupta (4): x86/entry_64: Add VERW just before userspace transition x86/entry_32: Add VERW just before userspace transition x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key KVM/VMX: Move VERW closer to VMentry for MDS mitigation Sean Christopherson (1): KVM/VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH Documentation/arch/x86/mds.rst | 38 +++++++++++++++++++++++++----------- arch/x86/entry/entry_32.S | 3 +++ arch/x86/entry/entry_64.S | 11 +++++++++++ arch/x86/entry/entry_64_compat.S | 1 + arch/x86/include/asm/entry-common.h | 1 - arch/x86/include/asm/nospec-branch.h | 12 ------------ arch/x86/kernel/cpu/bugs.c | 15 ++++++-------- arch/x86/kernel/nmi.c | 3 --- arch/x86/kvm/vmx/run_flags.h | 7 +++++-- arch/x86/kvm/vmx/vmenter.S | 9 ++++++--- arch/x86/kvm/vmx/vmx.c | 20 +++++++++++++++---- 11 files changed, 75 insertions(+), 45 deletions(-) --- base-commit: 9b4a8eac17f0d840729384618b4b1e876233026c change-id: 20240226-delay-verw-backport-6-6-y-2cda3298e600 Best regards, -- Thanks, Pawan
