Moving beyond pseudo-code and into compiles-but-probably-broken-code.
The intent of the functions below is that Fenghua should be able to
do:
void fpu__pasid_write(u32 pasid)
{
u64 msr_val = pasid | MSR_IA32_PASID_VALID;
struct ia32_pasid_state *addr;
addr = begin_update_one_xsave_feature(current, XFEATURE_PASID, true);
addr->pasid = msr_val;
finish_update_one_xsave_feature(current);
}
So here's the two new functions that would be added to
arch/x86/kernel/fpu/xstate.c
----
void *begin_update_one_xsave_feature(struct task_struct *tsk,
enum xfeature xfeature, bool full)
{
struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
struct xregs_state *xinit = &init_fpstate.xsave;
u64 fmask = 1ull << xfeature;
void *addr;
BUG_ON(!(xsave->header.xcomp_bv & fmask));
fpregs_lock();
addr = __raw_xsave_addr(xsave, xfeature);
if (full || tsk != current) {
memcpy(addr, __raw_xsave_addr(xinit, xfeature),
xstate_sizes[xfeature]);
goto out;
}
/* could optimize some cases where xsaves() isn't fastest option */
if (!(xsave->header.xfeatures & fmask))
xsaves(xsave, fmask);
out:
xsave->header.xfeatures |= fmask;
return addr;
}
void finish_update_one_xsave_feature(struct task_struct *tsk)
{
set_ti_thread_flag(task_thread_info(tsk), TIF_NEED_FPU_LOAD);
fpregs_unlock();
}
----
-Tony
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