On 2/21/2023 8:36 AM, Mingwei Zhang wrote:
Avoid getting xstate address of init_fpstate if fpstate contains the xstate
component. Since XTILEDATA (bit 18) was turned off in xinit, when KVM calls
__raw_xsave_addr(xinit, 18), it triggers a warning as follows.
__raw_xsave_addr() is an internal function that assume caller does the
checking, ie., all function arguments should be checked before calling.
So, instead of removing the WARNING, add checks in
__copy_xstate_to_uabi_buf().
<snip>
@@ -1151,10 +1152,11 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
pkru.pkru = pkru_val;
membuf_write(&to, &pkru, sizeof(pkru));
} else {
- copy_feature(header.xfeatures & BIT_ULL(i), &to,
- __raw_xsave_addr(xsave, i),
- __raw_xsave_addr(xinit, i),
- xstate_sizes[i]);
+ xsave_addr = (header.xfeatures & BIT_ULL(i)) ?
+ __raw_xsave_addr(xsave, i) :
+ __raw_xsave_addr(xinit, i);
+
+ membuf_write(&to, xsave_addr, xstate_sizes[i]);
}
/*
* Keep track of the last copied state in the non-compacted
So this hunk is under for_each_extended_xfeature(i, mask) -- it skips
the copy routine if mask[i] == 0; instead, it fills zeros.
We have this [1]:
if (fpu_state_size_dynamic())
mask &= (header.xfeatures | xinit->header.xcomp_bv);
If header.xfeatures[18] = 0 then mask[18] = 0 because
xinit->header.xcomp_bv[18] = 0. Then, it won't hit that code. So, I'm
confused about the problem that you described here.
Can you elaborate on your test case a bit? Let me try to reproduce the
issue on my end.
Thanks,
Chang
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/fpu/xstate.c#n1134
