diff options
Diffstat (limited to 'gitlab/issues_text/target_arm/host_missing/accel_missing/2304')
| -rw-r--r-- | gitlab/issues_text/target_arm/host_missing/accel_missing/2304 | 38 |
1 files changed, 0 insertions, 38 deletions
diff --git a/gitlab/issues_text/target_arm/host_missing/accel_missing/2304 b/gitlab/issues_text/target_arm/host_missing/accel_missing/2304 deleted file mode 100644 index 29de268d7..000000000 --- a/gitlab/issues_text/target_arm/host_missing/accel_missing/2304 +++ /dev/null @@ -1,38 +0,0 @@ -Disabling SVE via `-cpu max,sve=off` leaves SVE2 advertised by `getauxval` -Description of problem: -The documentation on https://qemu-project.gitlab.io/qemu/system/arm/cpu-features.html suggests that it should be possible to disable SVE support by passing `-cpu max,sve=off` on the command line, however this appears to only disable the SVE support advertised in the return value from `getauxval(AT_HWCAP)`. In particular it leaves SVE2 reported as enabled. This leaves the feature set advertised by `getauxval` in an inconsistent state since SVE is mandatory if SVE2 is available. - -This may also affect other feature dependencies for example FEAT_SVE_BITPerm also requiring SVE2 to be available, I've not checked exhaustively. - -For example, given the following code: - - #include <sys/auxv.h> - #include <stdio.h> - - int main() { - unsigned long hwcap = getauxval(AT_HWCAP); - unsigned long hwcap2 = getauxval(AT_HWCAP2); - - if (hwcap & HWCAP_SVE) { - printf("have sve!\n"); - } else { - printf("don't have sve!\n"); - } - if (hwcap2 & HWCAP2_SVE2) { - printf("have sve2!\n"); - } else { - printf("don't have sve2!\n"); - } - } - -We can observe the following: - - $ aarch64-linux-gnu-gcc test.c -static - $ ../qemu-aarch64 -cpu max ./a.out - have sve! - have sve2! - $ ../qemu-aarch64 -cpu max,sve=off ./a.out - don't have sve! - have sve2! - -I don't believe that there is a `-cpu ...,sve2=off` option, so I would expect that disabling SVE also prevents SVE2 from being advertised as available. |