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From: | Philippe Mathieu-Daudé |
Subject: | Re: [Qemu-devel] [PATCH 6/8] tcg/tci: disable MTTCG if TCI is enabled |
Date: | Thu, 3 Aug 2017 14:40:10 -0300 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 |
On 07/26/2017 05:02 AM, Alex Bennée wrote:
Philippe Mathieu-Daudé <address@hidden> writes:Hi Peter, I think this patch belongs to 2.10, as there is no time to fix TCI + MTTCG. Should I RESEND it alone with "for 2.10" subject? One other option might be disable TCI if MTTCG enabled, but there is no ./configure option for MTTCG while there is for TCI. Regards, Phil. On 06/28/2017 10:02 PM, Philippe Mathieu-Daudé wrote:TCI + MTTCG cause strange errors... $ arm-softmmu/qemu-system-arm -machine raspi2 -cpu cortex-a7 -smp 4 -accel tcg,thread=multi -kernel kernel7.img qemu-system-arm: Guest expects a stronger memory ordering than the host provides This may cause strange/hard to debug errors Segmentation fault (core dumped)So this isn't TCI enabling MTTCG by accident - this is the user forcing it when it wouldn't otherwise be enabled. Hence the scary warning...
Hmmm this is the user enabling TCI, I'm not sure about "forcing it".Now MTTCG is enforced by the ./configure and there is no option to disable it.
I posted this patch after realizing there are more TCI users/testers than just Stefan Weil, Jaroslaw Pelczar and me. Peter commented about http://qira.me/ which doesn't look very active. (see this thread: http://lists.nongnu.org/archive/html/qemu-devel/2017-06/threads.html#06528 )
Thinking about eventual downstream project using the TCI part of QEMU and trying to stay up-to-date with upstream, this patch might save headaches.
Since there is no formal yes/no to this patch I'm still wondering if I should track it or no.
Regards, Phil.
Signed-off-by: Philippe Mathieu-Daudé <address@hidden> --- configure | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/configure b/configure index c571ad14e5..510f443e06 100755 --- a/configure +++ b/configure @@ -6225,7 +6225,11 @@ fi if test "$target_softmmu" = "yes" ; then echo "CONFIG_SOFTMMU=y" >> $config_target_mak if test "$mttcg" = "yes" ; then - echo "TARGET_SUPPORTS_MTTCG=y" >> $config_target_mak + if test "$tcg_interpreter" = "yes" ; then + echo "TCI enabled, disabling MTTCG" + else + echo "TARGET_SUPPORTS_MTTCG=y" >> $config_target_mak + fi fi fi if test "$target_user_only" = "yes" ; then-- Alex Bennée
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