[tip: perf/urgent] x86/perf: Avoid warning for Arch LBR without XSAVE

[tip-bot2 for Andi Kleen]

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     8c16dc047b5dd8f7b3bf4584fa75733ea0dde7dc
Gitweb:        https://git.kernel.org/tip/8c16dc047b5dd8f7b3bf4584fa75733ea0dde7dc
Author:        Andi Kleen <ak@xxxxxxxxxxxxxxx>
AuthorDate:    Wed, 15 Dec 2021 12:40:29 -08:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 18 Jan 2022 12:09:49 +01:00

x86/perf: Avoid warning for Arch LBR without XSAVE

Some hypervisors support Arch LBR, but without the LBR XSAVE support.
The current Arch LBR init code prints a warning when the xsave size (0) is
unexpected. Avoid printing the warning for the "no LBR XSAVE" case.

Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20211215204029.150686-1-ak@xxxxxxxxxxxxxxx
---
 arch/x86/events/intel/lbr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index f8fd255..669c2be 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -1751,6 +1751,9 @@ static bool is_arch_lbr_xsave_available(void)
 	 * Check the LBR state with the corresponding software structure.
 	 * Disable LBR XSAVES support if the size doesn't match.
 	 */
+	if (xfeature_size(XFEATURE_LBR) == 0)
+		return false;
+
 	if (WARN_ON(xfeature_size(XFEATURE_LBR) != get_lbr_state_size()))
 		return false;