linux-kernel - [RFC v2 25/32] x86/tdx: Forcefully disable legacy PIC for TDX guests

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Message-Id: <b29f00c1eb5cff585ec2b999b69923c13418ecc4.1619458733.git.sathyanarayanan.kuppuswamy@linux.intel.com>
Date:   Mon, 26 Apr 2021 11:01:52 -0700
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>,
        Dan Williams <dan.j.williams@...el.com>,
        Tony Luck <tony.luck@...el.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        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 v2 25/32] 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 ab1efa4d10e9..1f1bb98e1d38 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -4,6 +4,7 @@
 #define pr_fmt(fmt) "TDX: " fmt
 
 #include <asm/tdx.h>
+#include <asm/i8259.h>
 #include <asm/vmx.h>
 #include <asm/insn.h>
 #include <linux/sched/signal.h> /* force_sig_fault() */
@@ -421,6 +422,8 @@ 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