linux-kernel - [RFC PATCH 68/73] x86/pvm: Implement irq related PVOPS

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Date: Mon, 26 Feb 2024 22:36:25 +0800
From: Lai Jiangshan <jiangshanlai@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <jiangshan.ljs@...group.com>,
	Hou Wenlong <houwenlong.hwl@...group.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	Ingo Molnar <mingo@...hat.com>,
	kvm@...r.kernel.org,
	Paolo Bonzini <pbonzini@...hat.com>,
	x86@...nel.org,
	Kees Cook <keescook@...omium.org>,
	Juergen Gross <jgross@...e.com>,
	Andy Lutomirski <luto@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [RFC PATCH 68/73] x86/pvm: Implement irq related PVOPS

From: Lai Jiangshan <jiangshan.ljs@...group.com>

The save_fl(), irq_enable(), and irq_disable() functions are in the hot
path, so the hypervisor shares the X86_EFLAG_IF status in the PVCS
structure for the guest kernel. This allows it to be read and modified
directly without a VM exit if there is no IRQ window request.
Additionally, the irq_halt() function remains the same, and a hypercall
is used in its PVOPS to enhance performance.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@...group.com>
---
 arch/x86/entry/entry_64_pvm.S   | 22 ++++++++++++++++++++++
 arch/x86/include/asm/pvm_para.h |  3 +++
 arch/x86/kernel/pvm.c           | 10 ++++++++++
 3 files changed, 35 insertions(+)

diff --git a/arch/x86/entry/entry_64_pvm.S b/arch/x86/entry/entry_64_pvm.S
index abb57e251e73..1d17bac2909a 100644
--- a/arch/x86/entry/entry_64_pvm.S
+++ b/arch/x86/entry/entry_64_pvm.S
@@ -65,6 +65,28 @@ SYM_FUNC_START(pvm_hypercall)
 	popq	%r11
 	RET
 SYM_FUNC_END(pvm_hypercall)
+
+SYM_FUNC_START(pvm_save_fl)
+	movq	PER_CPU_VAR(pvm_vcpu_struct + PVCS_event_flags), %rax
+	RET
+SYM_FUNC_END(pvm_save_fl)
+
+SYM_FUNC_START(pvm_irq_disable)
+	btrq	$X86_EFLAGS_IF_BIT, PER_CPU_VAR(pvm_vcpu_struct + PVCS_event_flags)
+	RET
+SYM_FUNC_END(pvm_irq_disable)
+
+SYM_FUNC_START(pvm_irq_enable)
+	/* set X86_EFLAGS_IF */
+	orq	$X86_EFLAGS_IF, PER_CPU_VAR(pvm_vcpu_struct + PVCS_event_flags)
+	btq	$PVM_EVENT_FLAGS_IP_BIT, PER_CPU_VAR(pvm_vcpu_struct + PVCS_event_flags)
+	jc	.L_maybe_interrupt_pending
+	RET
+.L_maybe_interrupt_pending:
+	/* handle pending IRQ */
+	movq	$PVM_HC_IRQ_WIN, %rax
+	jmp	pvm_hypercall
+SYM_FUNC_END(pvm_irq_enable)
 .popsection
 
 /*
diff --git a/arch/x86/include/asm/pvm_para.h b/arch/x86/include/asm/pvm_para.h
index f5d40a57c423..9484a1a23568 100644
--- a/arch/x86/include/asm/pvm_para.h
+++ b/arch/x86/include/asm/pvm_para.h
@@ -95,6 +95,9 @@ void pvm_user_event_entry(void);
 void pvm_hypercall(void);
 void pvm_retu_rip(void);
 void pvm_rets_rip(void);
+void pvm_save_fl(void);
+void pvm_irq_disable(void);
+void pvm_irq_enable(void);
 #endif /* !__ASSEMBLY__ */
 
 #endif /* _ASM_X86_PVM_PARA_H */
diff --git a/arch/x86/kernel/pvm.c b/arch/x86/kernel/pvm.c
index 12a35bef9bb8..b4522947374d 100644
--- a/arch/x86/kernel/pvm.c
+++ b/arch/x86/kernel/pvm.c
@@ -148,6 +148,11 @@ static void pvm_load_tls(struct thread_struct *t, unsigned int cpu)
 	}
 }
 
+static noinstr void pvm_safe_halt(void)
+{
+	pvm_hypercall0(PVM_HC_IRQ_HALT);
+}
+
 void __init pvm_early_event(struct pt_regs *regs)
 {
 	int vector = regs->orig_ax >> 32;
@@ -387,6 +392,11 @@ void __init pvm_early_setup(void)
 	pv_ops.cpu.write_msr_safe = pvm_write_msr_safe;
 	pv_ops.cpu.load_tls = pvm_load_tls;
 
+	pv_ops.irq.save_fl = __PV_IS_CALLEE_SAVE(pvm_save_fl);
+	pv_ops.irq.irq_disable = __PV_IS_CALLEE_SAVE(pvm_irq_disable);
+	pv_ops.irq.irq_enable = __PV_IS_CALLEE_SAVE(pvm_irq_enable);
+	pv_ops.irq.safe_halt = pvm_safe_halt;
+
 	wrmsrl(MSR_PVM_VCPU_STRUCT, __pa(this_cpu_ptr(&pvm_vcpu_struct)));
 	wrmsrl(MSR_PVM_EVENT_ENTRY, (unsigned long)(void *)pvm_early_kernel_event_entry - 256);
 	wrmsrl(MSR_PVM_SUPERVISOR_REDZONE, PVM_SUPERVISOR_REDZONE_SIZE);
-- 
2.19.1.6.gb485710b