From d446b472cc5051c2ef4eaf5f895d96d7a458c8a1 Mon Sep 17 00:00:00 2001 From: Matthew Barnes Date: Thu, 8 Aug 2024 13:53:40 +0200 Subject: [PATCH] x86/emul: Fix misaligned IO breakpoint behaviour in PV guests When hardware breakpoints are configured on misaligned IO ports, the hardware will mask the addresses based on the breakpoint width during comparison. For PV guests, misaligned IO breakpoints do not behave the same way, and therefore yield different results. This patch tweaks the emulation of IO breakpoints for PV guests such that they reproduce the same behaviour as hardware. Fixes: bec9e3205018 ("x86: emulate I/O port access breakpoints") Signed-off-by: Matthew Barnes Reviewed-by: Jan Beulich master commit: 08aacc392d86d4c7dbebdb5e664060ae2af72057 master date: 2024-08-08 13:27:50 +0200 --- xen/arch/x86/pv/emul-priv-op.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/xen/arch/x86/pv/emul-priv-op.c b/xen/arch/x86/pv/emul-priv-op.c index f101510a1b..aa11ecadaa 100644 --- a/xen/arch/x86/pv/emul-priv-op.c +++ b/xen/arch/x86/pv/emul-priv-op.c @@ -346,6 +346,8 @@ static unsigned int check_guest_io_breakpoint(struct vcpu *v, case DR_LEN_8: width = 8; break; } + start &= ~(width - 1UL); + if ( (start < (port + len)) && ((start + width) > port) ) match |= 1u << i; }