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Diffstat (limited to 'results/classifier/105/graphic/1915327')
| -rw-r--r-- | results/classifier/105/graphic/1915327 | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/results/classifier/105/graphic/1915327 b/results/classifier/105/graphic/1915327 new file mode 100644 index 000000000..78f7fe285 --- /dev/null +++ b/results/classifier/105/graphic/1915327 @@ -0,0 +1,80 @@ +graphic: 0.904 +instruction: 0.835 +mistranslation: 0.822 +other: 0.820 +semantic: 0.810 +device: 0.773 +assembly: 0.619 +network: 0.607 +vnc: 0.570 +socket: 0.508 +boot: 0.419 +KVM: 0.401 + +x86_64 cmpxchg behavior in qemu tcg does not match the real CPU + +QEMU version: +1214d55d1c (HEAD, origin/master, origin/HEAD) Merge remote-tracking branch 'remotes/nvme/tags/nvme-next-pull-request' into staging + +Consider the following little program: + +$ cat 1.c +#include <stdio.h> +int main() { + int mem = 0x12345678; + register long rax asm("rax") = 0x1234567812345678; + register int edi asm("edi") = 0x77777777; + asm("cmpxchg %[edi],%[mem]" + : [ mem ] "+m"(mem), [ rax ] "+r"(rax) + : [ edi ] "r"(edi)); + long rax2 = rax; + printf("rax2 = %lx\n", rax2); +} + +According to the Intel Manual, cmpxchg should not touch the accumulator in case the values are equal, which is indeed the case on the real CPU: + +$ gcc 1.c +$ ./a.out +rax2 = 1234567812345678 + +However, QEMU appears to zero extend EAX to RAX: + +$ qemu-x86_64 ./a.out +rax2 = 12345678 + +This is also the case for lock cmpxchg. + +Found in BPF development context: https://lore<email address hidden> + +The QEMU project is currently moving its bug tracking to another system. +For this we need to know which bugs are still valid and which could be +closed already. Thus we are setting the bug state to "Incomplete" now. + +If the bug has already been fixed in the latest upstream version of QEMU, +then please close this ticket as "Fix released". + +If it is not fixed yet and you think that this bug report here is still +valid, then you have two options: + +1) If you already have an account on gitlab.com, please open a new ticket +for this problem in our new tracker here: + + https://gitlab.com/qemu-project/qemu/-/issues + +and then close this ticket here on Launchpad (or let it expire auto- +matically after 60 days). Please mention the URL of this bug ticket on +Launchpad in the new ticket on GitLab. + +2) If you don't have an account on gitlab.com and don't intend to get +one, but still would like to keep this ticket opened, then please switch +the state back to "New" or "Confirmed" within the next 60 days (other- +wise it will get closed as "Expired"). We will then eventually migrate +the ticket automatically to the new system (but you won't be the reporter +of the bug in the new system and thus you won't get notified on changes +anymore). + +Thank you and sorry for the inconvenience. + + +[Expired for QEMU because there has been no activity for 60 days.] + |