On 10/13/21 11:13 PM, Lai Jiangshan wrote:
From: Lai Jiangshan <[email protected]> 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 <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Juergen Gross <[email protected]> Cc: Peter Anvin <[email protected]> Cc: [email protected]> Cc: Boris Ostrovsky <[email protected]> Signed-off-by: Lai Jiangshan <[email protected]>
Reviewed-by: Boris Ostrovsky <[email protected]>
