Re: [PATCH v3] KVM/x86: Move definition of __ex to x86.h

From: Krish Sadhukhan
Date: Mon Dec 21 2020 - 17:01:56 EST



On 12/21/20 11:48 AM, Uros Bizjak wrote:
Merge __kvm_handle_fault_on_reboot with its sole user
and move the definition of __ex to a common include to be
shared between VMX and SVM.

v2: Rebase to the latest kvm/queue.

v3: Incorporate changes from review comments.

Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 25 -------------------------
arch/x86/kvm/svm/sev.c | 2 --
arch/x86/kvm/svm/svm.c | 2 --
arch/x86/kvm/vmx/vmx.c | 4 +---
arch/x86/kvm/vmx/vmx_ops.h | 4 +---
arch/x86/kvm/x86.h | 24 ++++++++++++++++++++++++
6 files changed, 26 insertions(+), 35 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 39707e72b062..a78e4b1a5d77 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1634,31 +1634,6 @@ enum {
#define kvm_arch_vcpu_memslots_id(vcpu) ((vcpu)->arch.hflags & HF_SMM_MASK ? 1 : 0)
#define kvm_memslots_for_spte_role(kvm, role) __kvm_memslots(kvm, (role).smm)
-asmlinkage void kvm_spurious_fault(void);
-
-/*
- * Hardware virtualization extension instructions may fault if a
- * reboot turns off virtualization while processes are running.
- * Usually after catching the fault we just panic; during reboot
- * instead the instruction is ignored.
- */
-#define __kvm_handle_fault_on_reboot(insn) \
- "666: \n\t" \
- insn "\n\t" \
- "jmp 668f \n\t" \
- "667: \n\t" \
- "1: \n\t" \
- ".pushsection .discard.instr_begin \n\t" \
- ".long 1b - . \n\t" \
- ".popsection \n\t" \
- "call kvm_spurious_fault \n\t" \
- "1: \n\t" \
- ".pushsection .discard.instr_end \n\t" \
- ".long 1b - . \n\t" \
- ".popsection \n\t" \
- "668: \n\t" \
- _ASM_EXTABLE(666b, 667b)
-
#define KVM_ARCH_WANT_MMU_NOTIFIER
int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end,
unsigned flags);
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index e57847ff8bd2..ba492b6d37a0 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -25,8 +25,6 @@
#include "cpuid.h"
#include "trace.h"
-#define __ex(x) __kvm_handle_fault_on_reboot(x)
-
static u8 sev_enc_bit;
static int sev_flush_asids(void);
static DECLARE_RWSEM(sev_deactivate_lock);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 941e5251e13f..733d9f98a121 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -42,8 +42,6 @@
#include "svm.h"
-#define __ex(x) __kvm_handle_fault_on_reboot(x)
-
MODULE_AUTHOR("Qumranet");
MODULE_LICENSE("GPL");
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 75c9c6a0a3a4..b82f2689f2d7 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2320,9 +2320,7 @@ static void vmclear_local_loaded_vmcss(void)
}
-/* Just like cpu_vmxoff(), but with the __kvm_handle_fault_on_reboot()
- * tricks.
- */
+/* Just like cpu_vmxoff(), but with the fault handling. */
static void kvm_cpu_vmxoff(void)
{
asm volatile (__ex("vmxoff"));
diff --git a/arch/x86/kvm/vmx/vmx_ops.h b/arch/x86/kvm/vmx/vmx_ops.h
index 692b0c31c9c8..7e3cb53c413f 100644
--- a/arch/x86/kvm/vmx/vmx_ops.h
+++ b/arch/x86/kvm/vmx/vmx_ops.h
@@ -4,13 +4,11 @@
#include <linux/nospec.h>
-#include <asm/kvm_host.h>
#include <asm/vmx.h>
#include "evmcs.h"
#include "vmcs.h"
-
-#define __ex(x) __kvm_handle_fault_on_reboot(x)
+#include "x86.h"
asmlinkage void vmread_error(unsigned long field, bool fault);
__attribute__((regparm(0))) void vmread_error_trampoline(unsigned long field,
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index c5ee0f5ce0f1..5b16d2b5c3bc 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -8,6 +8,30 @@
#include "kvm_cache_regs.h"
#include "kvm_emulate.h"
+asmlinkage void kvm_spurious_fault(void);
+
+/*
+ * Handle a fault on a hardware virtualization (VMX or SVM) instruction.
+ *
+ * Hardware virtualization extension instructions may fault if a reboot turns
+ * off virtualization while processes are running. Usually after catching the
+ * fault we just panic; during reboot instead the instruction is ignored.
+ */
+#define __ex(insn) \


While the previous name was too elaborate, this new name is very cryptic.  Unless we are saving for space, it's better to give a somewhat descriptive name.

+ "666: " insn "\n" \
+ " jmp 669f\n" \
+ "667:\n" \
+ " .pushsection .discard.instr_begin\n" \
+ " .long 667b - .\n" \
+ " .popsection\n" \
+ " call kvm_spurious_fault\n" \
+ "668:\n" \
+ " .pushsection .discard.instr_end\n" \
+ " .long 668b - .\n" \
+ " .popsection\n" \
+ "669:\n" \
+ _ASM_EXTABLE(666b, 667b)
+
#define KVM_DEFAULT_PLE_GAP 128
#define KVM_VMX_DEFAULT_PLE_WINDOW 4096
#define KVM_DEFAULT_PLE_WINDOW_GROW 2