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graphic: 0.541
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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.
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