perf/x86: Enable XMM register sampling for REGS_USER case

Support XMM register sampling for the REGS_USER case.

To handle simultaneous sampling of XMM registers for both REGS_INTR and
REGS_USER cases, a per-CPU x86_user_regs is introduced to store
REGS_USER-specific XMM registers. This prevents REGS_USER-specific XMM
register data from being overwritten by REGS_INTR-specific data if they
share the same x86_perf_regs structure.

To sample user-space XMM registers, the x86_pmu_update_user_xregs()
helper function is added. It checks if the user-space FPU state has been
cached into task FPU state. If so, the user-space XMM register data
can be directly retrieved from the cached task FPU state, as the
corresponding hardware registers have been cleared or switched to
kernel-space state or guest state. Otherwise, the data could be read
from the hardware registers using the xsaves instruction.

For PEBS events, x86_pmu_update_user_xregs() checks if the PEBS-sampled
XMM register data belongs to user-space. If so, no further action is
needed. Otherwise, the user-space XMM register data needs to be
re-sampled using the same method as for non-PEBS events.

Co-developed-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260824082731.1013973-12-dapeng1.mi@linux.intel.com

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