On 06.07.20 10:41, Michal Kubecek wrote:
On Fri, Jul 03, 2020 at 10:02:55AM -0700, Andy Lutomirski wrote:
On Xen PV, #DB doesn't use IST. We still need to correctly route it
depending on whether it came from user or kernel mode.
This patch gets rid of DECLARE/DEFINE_IDTENTRY_XEN -- it was too
hard to follow the logic. Instead, route #DB and NMI through
DECLARE/DEFINE_IDTENTRY_RAW on Xen, and do the right thing for #DB.
Also add more warnings to the exc_debug* handlers to make this type
of failure more obvious.
This fixes various forms of corruption that happen when usermode
triggers #DB on Xen PV.
Fixes: 4c0dcd8350a0 ("x86/entry: Implement user mode C entry points for #DB and
#MCE")
Signed-off-by: Andy Lutomirski <l...@kernel.org>
---
arch/x86/include/asm/idtentry.h | 24 ++++++------------------
arch/x86/kernel/traps.c | 12 ++++++++++++
arch/x86/xen/enlighten_pv.c | 28 ++++++++++++++++++++++++----
arch/x86/xen/xen-asm_64.S | 5 ++---
4 files changed, 44 insertions(+), 25 deletions(-)
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index cf51c50eb356..94333ac3092b 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
[...]
@@ -570,11 +554,15 @@ DECLARE_IDTENTRY_MCE(X86_TRAP_MC, exc_machine_check);
/* NMI */
DECLARE_IDTENTRY_NMI(X86_TRAP_NMI, exc_nmi);
-DECLARE_IDTENTRY_XEN(X86_TRAP_NMI, nmi);
+#ifdef CONFIG_XEN_PV
+DECLARE_IDTENTRY_RAW(X86_TRAP_NMI, xenpv_exc_nmi);
+#endif
/* #DB */
DECLARE_IDTENTRY_DEBUG(X86_TRAP_DB, exc_debug);
-DECLARE_IDTENTRY_XEN(X86_TRAP_DB, debug);
+#ifdef CONFIG_XEN_PV
+DECLARE_IDTENTRY_RAW(X86_TRAP_DB, xenpv_exc_debug);
+#endif
/* #DF */
DECLARE_IDTENTRY_DF(X86_TRAP_DF, exc_double_fault);
Hello,
this patch - now in mainline as commit 13cbc0cd4a30 ("x86/entry/32: Fix
#MC and #DB wiring on x86_32") - seems to break i586 builds with
CONFIG_XEN_PV=y as xenpv_exc_nmi and xenpv_exc_debug are only defined
with CONFIG_X86_64:
[ 1279s] ld: arch/x86/entry/entry_32.o: in function `asm_xenpv_exc_nmi':
[ 1279s]
/home/abuild/rpmbuild/BUILD/kernel-pae-5.8.rc4/linux-5.8-rc4/linux-obj/../arch/x86/include/asm/idtentry.h:557:
undefined reference to `xenpv_exc_nmi'
[ 1279s] ld: arch/x86/entry/entry_32.o: in function `asm_xenpv_exc_debug':
[ 1279s]
/home/abuild/rpmbuild/BUILD/kernel-pae-5.8.rc4/linux-5.8-rc4/linux-obj/../arch/x86/include/asm/idtentry.h:567:
undefined reference to `xenpv_exc_debug'
Fix is already queued in tip/tip.git x86/urgent
Juergen
