linux-kernel - [PATCH] x86/perf: Avoid warning for Arch LBR without XSAVE

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Message-Id: <20211215204029.150686-1-ak@linux.intel.com>
Date:   Wed, 15 Dec 2021 12:40:29 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org, kan.liang@...ux.intel.com,
        Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH] 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@...ux.intel.com>
---
 arch/x86/events/intel/lbr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 8043213b75a5..1b8fef8545fb 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -1726,6 +1726,8 @@ 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;
 
-- 
2.33.1