Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 5.18 04/61] x86/entry: Dont call error_entry() for XENPV | Date | Tue, 12 Jul 2022 20:39:01 +0200 |
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From: Lai Jiangshan <jiangshan.ljs@antgroup.com>
commit 64cbd0acb58203fb769ed2f4eab526d43e243847 upstream.
XENPV guests enter already on the task stack and they can't fault for native_iret() nor native_load_gs_index() since they use their own pvop for IRET and load_gs_index(). A CR3 switch is not needed either.
So there is no reason to call error_entry() in XENPV.
[ bp: Massage commit message. ]
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Juergen Gross <jgross@suse.com> Link: https://lore.kernel.org/r/20220503032107.680190-6-jiangshanlai@gmail.com Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- arch/x86/entry/entry_64.S | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)
--- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -336,8 +336,17 @@ SYM_CODE_END(push_and_clear_regs) call push_and_clear_regs UNWIND_HINT_REGS - call error_entry - movq %rax, %rsp /* switch to the task stack if from userspace */ + /* + * Call error_entry() and switch to the task stack if from userspace. + * + * When in XENPV, it is already in the task stack, and it can't fault + * for native_iret() nor native_load_gs_index() since XENPV uses its + * own pvops for IRET and load_gs_index(). And it doesn't need to + * switch the CR3. So it can skip invoking error_entry(). + */ + ALTERNATIVE "call error_entry; movq %rax, %rsp", \ + "", X86_FEATURE_XENPV + ENCODE_FRAME_POINTER UNWIND_HINT_REGS
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