linux-kernel - [PATCH v3 4/5] x86/tdx: Forcefully disable legacy PIC for TDX guests

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Date:   Mon, 19 Jul 2021 21:09:00 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Cc:     Peter H Anvin <hpa@...or.com>, Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: [PATCH v3 4/5] x86/tdx: Forcefully disable legacy PIC for TDX guests

From: Sean Christopherson <sean.j.christopherson@...el.com>

Disable the legacy PIC (8259) for TDX guests as the PIC cannot be
supported by the VMM. TDX Module does not allow direct IRQ injection,
and using posted interrupt style delivery requires the guest to EOI
the IRQ, which diverges from the legacy PIC behavior.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
---
 arch/x86/kernel/tdx.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index a110bd5e5e4c..254997315a2f 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -8,6 +8,7 @@
 #include <linux/cpuhotplug.h>
 
 #include <asm/tdx.h>
+#include <asm/i8259.h>
 #include <asm/vmx.h>
 #include <asm/insn.h>
 #include <asm/insn-eval.h>
@@ -458,6 +459,8 @@ void __init tdx_early_init(void)
 	pv_ops.irq.safe_halt = tdg_safe_halt;
 	pv_ops.irq.halt = tdg_halt;
 
+	legacy_pic = &null_legacy_pic;
+
 	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "tdg:cpu_hotplug",
 			  NULL, tdg_cpu_offline_prepare);
 
-- 
2.25.1