perf/amd/ibs: Preserve PhyAddrVal bit when clearing PhyAddr MSR

[ Upstream commit 723a290 ]

Commit 50a53b6 ("perf/amd/ibs: Prevent leaking sensitive data to
userspace") zeroed the physical address and also cleared the PhyAddrVal
flag before copying the value into a perf sample to avoid exposing
physical addresses to unprivileged users.

Clearing PhyAddrVal, however, has an unintended side-effect: several
other IBS fields are considered valid only when this bit is set. As a
result, those otherwise correct fields are discarded, reducing IBS
functionality.

Continue to zero the physical address, but keep the PhyAddrVal bit
intact so the related fields remain usable while still preventing any
address leak.

Fixes: 50a53b6 ("perf/amd/ibs: Prevent leaking sensitive data to userspace")
Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: https://patch.msgid.link/20260216042216.1440-4-ravi.bangoria@amd.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Ravi Bangoria

arch/x86/events/amd/ibs.c

@@ -1214,12 +1214,10 @@ static void perf_ibs_phyaddr_clear(struct perf_ibs *perf_ibs,
 				   struct perf_ibs_data *ibs_data)
 {
 	if (perf_ibs == &perf_ibs_op) {
-		ibs_data->regs[ibs_op_msr_idx(MSR_AMD64_IBSOPDATA3)] &= ~(1ULL << 18);
 		ibs_data->regs[ibs_op_msr_idx(MSR_AMD64_IBSDCPHYSAD)] = 0;
 		return;
 	}
 
-	ibs_data->regs[ibs_fetch_msr_idx(MSR_AMD64_IBSFETCHCTL)] &= ~(1ULL << 52);
 	ibs_data->regs[ibs_fetch_msr_idx(MSR_AMD64_IBSFETCHPHYSAD)] = 0;
 }