From: Peter Maydell Date: Sun, 25 Jul 2021 17:44:04 +0000 (+0100) Subject: accel/tcg: Don't use CF_COUNT_MASK as the max value of icount_decr.u16.low X-Git-Tag: qemu-xen-4.16.0-rc4~41^2~11 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=df3a2de51a07089a4a729fe1f792f658df9dade4;p=qemu-xen.git accel/tcg: Don't use CF_COUNT_MASK as the max value of icount_decr.u16.low In cpu_loop_exec_tb() we were bounding the number of insns we might try to execute in a TB using CF_COUNT_MASK. This is incorrect, because we can validly put up to 0xffff into icount_decr.u16.low. In particular, since commit 78ff82bb1b67c0d7 reduced CF_COUNT_MASK to 511 this meant that we would incorrectly only try to execute 511 instructions in a 512-instruction TB, which could result in QEMU hanging when in icount mode. Use the actual maximum value, which is 0xffff. (This brings this code in to line with the similar logic in icount_prepare_for_run() in tcg-accel-ops-icount.c.) Fixes: 78ff82bb1b67c0d7 Signed-off-by: Peter Maydell Reviewed-by: Richard Henderson Reviewed-by: Philippe Mathieu-Daudé Resolves: https://gitlab.com/qemu-project/qemu/-/issues/499 Message-Id: <20210725174405.24568-2-peter.maydell@linaro.org> Signed-off-by: Richard Henderson --- diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index fc895cf51e..6e8dc29119 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -834,7 +834,7 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb, /* Ensure global icount has gone forward */ icount_update(cpu); /* Refill decrementer and continue execution. */ - insns_left = MIN(CF_COUNT_MASK, cpu->icount_budget); + insns_left = MIN(0xffff, cpu->icount_budget); cpu_neg(cpu)->icount_decr.u16.low = insns_left; cpu->icount_extra = cpu->icount_budget - insns_left;