Messages in this thread | | | Date | Sat, 16 Oct 2021 14:08:55 -0400 | Subject | Re: [PATCH V3 04/49] x86/xen: Add xenpv_restore_regs_and_return_to_usermode() | From | Boris Ostrovsky <> |
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On 10/13/21 11:13 PM, Lai Jiangshan wrote: > From: Lai Jiangshan <laijs@linux.alibaba.com> > > While in the native case, PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is the > trampoline stack. But XEN pv doesn't use trampoline stack, so > PER_CPU_VAR(cpu_tss_rw + TSS_sp0) is also the kernel stack. Hence source > and destination stacks are identical in that case, which means reusing > swapgs_restore_regs_and_return_to_usermode() in XEN pv would cause %rsp > to move up to the top of the kernel stack and leave the IRET frame below > %rsp, which is dangerous to be corrupted if #NMI / #MC hit as either of > these events occurring in the middle of the stack pushing would clobber > data on the (original) stack. > > And swapgs_restore_regs_and_return_to_usermode() pushing the IRET frame > on to the original address is useless and error-prone when there is any > future attempt to modify the code. > > Fixes: 7f2590a110b8 ("x86/entry/64: Use a per-CPU trampoline stack for IDT entries") > Cc: Jan Beulich <jbeulich@suse.com> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Juergen Gross <jgross@suse.com> > Cc: Peter Anvin <hpa@zytor.com> > Cc: xen-devel@lists.xenproject.org> > Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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