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

From: Uros Bizjak
Date: Mon Dec 21 2020 - 17:11:18 EST

On Mon, Dec 21, 2020 at 11:01 PM Krish Sadhukhan
<krish.sadhukhan@xxxxxxxxxx> wrote:
>
>
> 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.

Then we will need to update all usage sites to a new name, something I
tried to avoid.

Uros.

> > + "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