linux-kernel - [PATCH v5 05/16] x86/cpu: Defer CR pinning setup until after EFI initialization

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Message-ID: <20241028160917.1380714-6-alexander.shishkin@linux.intel.com>
Date: Mon, 28 Oct 2024 18:07:53 +0200
From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To: Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
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	Xin Li <xin3.li@...el.com>,
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	Brijesh Singh <brijesh.singh@....com>,
	Michael Roth <michael.roth@....com>,
	Tony Luck <tony.luck@...el.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Alexey Kardashevskiy <aik@....com>
Cc: Jonathan Corbet <corbet@....net>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
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Subject: [PATCH v5 05/16] x86/cpu: Defer CR pinning setup until after EFI initialization

In order to map the EFI runtime services, set_virtual_address_map
needs to be called, which resides in the lower half of the address
space. This means that LASS needs to be temporarily disabled around
this call. This can only be done before the CR pinning is set up.

Move CR pinning setup behind the EFI initialization.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Suggested-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/kernel/cpu/common.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index b24ad418536e..c249fd0aa3fb 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1953,7 +1953,6 @@ static __init void identify_boot_cpu(void)
 	enable_sep_cpu();
 #endif
 	cpu_detect_tlb(&boot_cpu_data);
-	setup_cr_pinning();
 
 	tsx_init();
 	tdx_init();
@@ -2385,10 +2384,16 @@ void __init arch_cpu_finalize_init(void)
 
 	/*
 	 * This needs to follow the FPU initializtion, since EFI depends on it.
+	 * It also needs to precede the CR pinning setup, because we need to be
+	 * able to temporarily clear the CR4.LASS bit in order to execute the
+	 * set_virtual_address_map call, which resides in lower addresses and
+	 * would trip LASS if enabled.
 	 */
 	if (efi_enabled(EFI_RUNTIME_SERVICES))
 		efi_enter_virtual_mode();
 
+	setup_cr_pinning();
+
 	/*
 	 * Ensure that access to the per CPU representation has the initial
 	 * boot CPU configuration.
-- 
2.45.2