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From: Lai Jiangshan <jiangshanlai@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Hou Wenlong <houwenlong.hwl@antgroup.com>,
	Lai Jiangshan <jiangshan.ljs@antgroup.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Sean Christopherson <seanjc@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>,
	Ingo Molnar <mingo@redhat.com>,
	kvm@vger.kernel.org,
	Paolo Bonzini <pbonzini@redhat.com>,
	x86@kernel.org,
	Kees Cook <keescook@chromium.org>,
	Juergen Gross <jgross@suse.com>,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Ajay Kaher <akaher@vmware.com>,
	Alexey Makhalov <amakhalov@vmware.com>,
	VMware PV-Drivers Reviewers <pv-drivers@vmware.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	"Mike Rapoport (IBM)" <rppt@kernel.org>,
	Daniel Sneddon <daniel.sneddon@linux.intel.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Alexey Kardashevskiy <aik@amd.com>,
	virtualization@lists.linux.dev,
	xen-devel@lists.xenproject.org
Subject: [RFC PATCH 66/73] x86/pvm: Use new cpu feature to describe XENPV and PVM
Date: Mon, 26 Feb 2024 22:36:23 +0800
Message-Id: <20240226143630.33643-67-jiangshanlai@gmail.com>
In-Reply-To: <20240226143630.33643-1-jiangshanlai@gmail.com>
References: <20240226143630.33643-1-jiangshanlai@gmail.com>
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From: Hou Wenlong <houwenlong.hwl@antgroup.com>

Some PVOPS are patched as the native version directly if the guest is
not a XENPV guest. However, this approach will not work after
introducing a PVM guest. To address this, use a new CPU feature to
describe XENPV and PVM, and ensure that those PVOPS are patched only
when it is not a paravirtual guest.

Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
 arch/x86/entry/entry_64.S          |  5 ++---
 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/include/asm/paravirt.h    | 14 +++++++-------
 arch/x86/kernel/pvm.c              |  1 +
 arch/x86/xen/enlighten_pv.c        |  1 +
 5 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index fe12605b3c05..6b41a1837698 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -127,9 +127,8 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe, SYM_L_GLOBAL)
 	 * In the PVM guest case we must use eretu synthetic instruction.
 	 */
 
-	ALTERNATIVE_2 "testb %al, %al; jz swapgs_restore_regs_and_return_to_usermode", \
-		"jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV, \
-		"jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_KVM_PVM_GUEST
+	ALTERNATIVE "testb %al, %al; jz swapgs_restore_regs_and_return_to_usermode", \
+		"jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_PV_GUEST
 
 	/*
 	 * We win! This label is here just for ease of understanding
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index e17e72f13423..72ef58a2db19 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -238,6 +238,7 @@
 #define X86_FEATURE_VCPUPREEMPT		( 8*32+21) /* "" PV vcpu_is_preempted function */
 #define X86_FEATURE_TDX_GUEST		( 8*32+22) /* Intel Trust Domain Extensions Guest */
 #define X86_FEATURE_KVM_PVM_GUEST	( 8*32+23) /* KVM Pagetable-based Virtual Machine guest */
+#define X86_FEATURE_PV_GUEST		( 8*32+24) /* "" Paravirtual guest */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */
 #define X86_FEATURE_FSGSBASE		( 9*32+ 0) /* RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index deaee9ec575e..a864ee481ca2 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -143,7 +143,7 @@ static __always_inline unsigned long read_cr2(void)
 {
 	return PVOP_ALT_CALLEE0(unsigned long, mmu.read_cr2,
 				"mov %%cr2, %%rax;",
-				ALT_NOT(X86_FEATURE_XENPV));
+				ALT_NOT(X86_FEATURE_PV_GUEST));
 }
 
 static __always_inline void write_cr2(unsigned long x)
@@ -154,13 +154,13 @@ static __always_inline void write_cr2(unsigned long x)
 static inline unsigned long __read_cr3(void)
 {
 	return PVOP_ALT_CALL0(unsigned long, mmu.read_cr3,
-			      "mov %%cr3, %%rax;", ALT_NOT(X86_FEATURE_XENPV));
+			      "mov %%cr3, %%rax;", ALT_NOT(X86_FEATURE_PV_GUEST));
 }
 
 static inline void write_cr3(unsigned long x)
 {
 	PVOP_ALT_VCALL1(mmu.write_cr3, x,
-			"mov %%rdi, %%cr3", ALT_NOT(X86_FEATURE_XENPV));
+			"mov %%rdi, %%cr3", ALT_NOT(X86_FEATURE_PV_GUEST));
 }
 
 static inline void __write_cr4(unsigned long x)
@@ -694,17 +694,17 @@ bool __raw_callee_save___native_vcpu_is_preempted(long cpu);
 static __always_inline unsigned long arch_local_save_flags(void)
 {
 	return PVOP_ALT_CALLEE0(unsigned long, irq.save_fl, "pushf; pop %%rax;",
-				ALT_NOT(X86_FEATURE_XENPV));
+				ALT_NOT(X86_FEATURE_PV_GUEST));
 }
 
 static __always_inline void arch_local_irq_disable(void)
 {
-	PVOP_ALT_VCALLEE0(irq.irq_disable, "cli;", ALT_NOT(X86_FEATURE_XENPV));
+	PVOP_ALT_VCALLEE0(irq.irq_disable, "cli;", ALT_NOT(X86_FEATURE_PV_GUEST));
 }
 
 static __always_inline void arch_local_irq_enable(void)
 {
-	PVOP_ALT_VCALLEE0(irq.irq_enable, "sti;", ALT_NOT(X86_FEATURE_XENPV));
+	PVOP_ALT_VCALLEE0(irq.irq_enable, "sti;", ALT_NOT(X86_FEATURE_PV_GUEST));
 }
 
 static __always_inline unsigned long arch_local_irq_save(void)
@@ -776,7 +776,7 @@ void native_pv_lock_init(void) __init;
 .endm
 
 #define SAVE_FLAGS	ALTERNATIVE "PARA_IRQ_save_fl;", "pushf; pop %rax;", \
-				    ALT_NOT(X86_FEATURE_XENPV)
+				    ALT_NOT(X86_FEATURE_PV_GUEST)
 #endif
 #endif /* CONFIG_PARAVIRT_XXL */
 #endif	/* CONFIG_X86_64 */
diff --git a/arch/x86/kernel/pvm.c b/arch/x86/kernel/pvm.c
index c38e46a96ad3..d39550a8159f 100644
--- a/arch/x86/kernel/pvm.c
+++ b/arch/x86/kernel/pvm.c
@@ -300,6 +300,7 @@ void __init pvm_early_setup(void)
 		return;
 
 	setup_force_cpu_cap(X86_FEATURE_KVM_PVM_GUEST);
+	setup_force_cpu_cap(X86_FEATURE_PV_GUEST);
 
 	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);
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index aeb33e0a3f76..c56483051528 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -335,6 +335,7 @@ static bool __init xen_check_xsave(void)
 static void __init xen_init_capabilities(void)
 {
 	setup_force_cpu_cap(X86_FEATURE_XENPV);
+	setup_force_cpu_cap(X86_FEATURE_PV_GUEST);
 	setup_clear_cpu_cap(X86_FEATURE_DCA);
 	setup_clear_cpu_cap(X86_FEATURE_APERFMPERF);
 	setup_clear_cpu_cap(X86_FEATURE_MTRR);
-- 
2.19.1.6.gb485710b