From 77b129a1c6fd1cc01394717218917cd98c231696 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Fri, 16 Feb 2018 16:07:30 -0500 Subject: [PATCH] target-i386: Re-introduce optimal breakpoint removal Before the last patch, we had an efficient loop that disabled local breakpoints on task switch. Re-add that, but in a more general way that handles changes to the global enable bits too. Backports commit 36eb6e096729f9aade3a6af7dbe4d0a990335d7e from qemu --- qemu/target-i386/bpt_helper.c | 34 ++++++++++++++++++++++++++++------ 1 file changed, 28 insertions(+), 6 deletions(-) diff --git a/qemu/target-i386/bpt_helper.c b/qemu/target-i386/bpt_helper.c index 5dfcb92a..5ce4ef1f 100644 --- a/qemu/target-i386/bpt_helper.c +++ b/qemu/target-i386/bpt_helper.c @@ -82,13 +82,35 @@ static void hw_breakpoint_remove(CPUX86State *env, int index) void cpu_x86_update_dr7(CPUX86State *env, uint32_t new_dr7) { int i; + target_ulong old_dr7 = env->dr[7]; - for (i = 0; i < DR7_MAX_BP; i++) { - hw_breakpoint_remove(env, i); - } - env->dr[7] = new_dr7; - for (i = 0; i < DR7_MAX_BP; i++) { - hw_breakpoint_insert(env, i); + /* If nothing is changing except the global/local enable bits, + then we can make the change more efficient. */ + if (((old_dr7 ^ new_dr7) & ~0xff) == 0) { + /* Fold the global and local enable bits together into the + global fields, then xor to show which registers have + changed collective enable state. */ + int mod = ((old_dr7 | old_dr7 * 2) ^ (new_dr7 | new_dr7 * 2)) & 0xff; + + for (i = 0; i < DR7_MAX_BP; i++) { + if ((mod & (2 << i * 2)) && !hw_breakpoint_enabled(new_dr7, i)) { + hw_breakpoint_remove(env, i); + } + } + env->dr[7] = new_dr7; + for (i = 0; i < DR7_MAX_BP; i++) { + if (mod & (2 << i * 2) && hw_breakpoint_enabled(new_dr7, i)) { + hw_breakpoint_insert(env, i); + } + } + } else { + for (i = 0; i < DR7_MAX_BP; i++) { + hw_breakpoint_remove(env, i); + } + env->dr[7] = new_dr7; + for (i = 0; i < DR7_MAX_BP; i++) { + hw_breakpoint_insert(env, i); + } } } #endif