linux-kernel - [RFC v1 19/26] x86/tdx: Forcefully disable legacy PIC for TDX guests

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Date:   Fri,  5 Feb 2021 15:38:36 -0800
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: [RFC v1 19/26] 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>
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 a36b6ae14942..ae37498df981 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -4,6 +4,7 @@
 #include <asm/tdx.h>
 #include <asm/cpufeature.h>
 #include <linux/cpu.h>
+#include <asm/i8259.h>
 #include <asm/tdx.h>
 #include <asm/vmx.h>
 #include <asm/insn.h>
@@ -410,6 +411,8 @@ void __init tdx_early_init(void)
 	pv_ops.irq.safe_halt = tdx_safe_halt;
 	pv_ops.irq.halt = tdx_halt;
 
+	legacy_pic = &null_legacy_pic;
+
 	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "tdx:cpu_hotplug",
 			  NULL, tdx_cpu_offline_prepare);
 
-- 
2.25.1