[tip: x86/msr] x86/msr: Don't use rdmsr_safe_on_cpu() in rdmsrq_safe_on_cpu()

[tip-bot2 for Juergen Gross]

The following commit has been merged into the x86/msr branch of tip:

Commit-ID:     dfaf45fba11642893ed3d28c1aa9f516330147f1
Gitweb:        https://git.kernel.org/tip/dfaf45fba11642893ed3d28c1aa9f516330147f1
Author:        Juergen Gross <jgross@xxxxxxxx>
AuthorDate:    Mon, 08 Jun 2026 07:17:37 +02:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Mon, 08 Jun 2026 10:01:49 +02:00

x86/msr: Don't use rdmsr_safe_on_cpu() in rdmsrq_safe_on_cpu()

In order to prepare removal of rdmsr_safe_on_cpu(), don't use it in
rdmsrq_safe_on_cpu(), but replace it with open coding it.

This will create a nearly verbatim copy of the same code, but this is
only temporary until rdmsr_safe_on_cpu() is removed.

Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Link: https://patch.msgid.link/20260608051741.3207435-8-jgross@xxxxxxxx
---
 arch/x86/lib/msr-smp.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/x86/lib/msr-smp.c b/arch/x86/lib/msr-smp.c
index a434c80..f3c75b6 100644
--- a/arch/x86/lib/msr-smp.c
+++ b/arch/x86/lib/msr-smp.c
@@ -190,11 +190,22 @@ EXPORT_SYMBOL(wrmsrq_safe_on_cpu);
 
 int rdmsrq_safe_on_cpu(unsigned int cpu, u32 msr_no, u64 *q)
 {
-	u32 low, high;
+	struct msr_info_completion rv;
+	call_single_data_t csd;
 	int err;
 
-	err = rdmsr_safe_on_cpu(cpu, msr_no, &low, &high);
-	*q = (u64)high << 32 | low;
+	INIT_CSD(&csd, __rdmsr_safe_on_cpu, &rv);
+
+	memset(&rv, 0, sizeof(rv));
+	init_completion(&rv.done);
+	rv.msr.msr_no = msr_no;
+
+	err = smp_call_function_single_async(cpu, &csd);
+	if (!err) {
+		wait_for_completion(&rv.done);
+		err = rv.msr.err;
+	}
+	*q = rv.msr.reg.q;
 
 	return err;
 }