Re: [PATCH] KVM: nVMX: Fix some comment typos and coding style

Re: [PATCH] KVM: nVMX: Fix some comment typos and coding style

[linmiaohe]

Hi:
Sean Christopherson <sean.j.christopherson@intel.com> wrote:
> On Thu, Feb 06, 2020 at 12:32:38PM +0100, Vitaly Kuznetsov wrote:
>> linmiaohe <linmiaohe@huawei.com> writes:
>> 
>> 
>> I have to admit that shadow MMU in KVM is not my strong side but this 
>> comment reads weird, I'd appreciate if someone could suggest a better 
>> alternative.
>
>	/* One off flag for a stupid corner case in shadow paging. */
>> 
>> >  	 */
>
>	/*
>	 * Indicates the guest is trying to write a gfn that contains one or
>	 * more of the PTEs used to translate the write itself, i.e. the access
>	 * is changing its own translation in the guest page tables.  KVM exits
>	 * to userspace if emulation of the faulting instruction fails and this
>	 * flag is set, as KVM cannot make forward progress.
>	 *
>	 * If emulation fails for a write to guest page tables, KVM unprotects
>	 * (zaps) the shadow page for the target gfn and resumes the guest to
>	 * retry the non-emulatable instruction (on hardware).  Unprotecting the
>	 * gfn doesn't allow forward progress for a self-changing access because
>	 * doing so also zaps the translation for the gfn, i.e. retrying the
>	 * instruction will hit a !PRESENT fault, which results in a new shadow
>	 * page and sends KVM back to square one.
>	 */
>> >  	bool write_fault_to_shadow_pgtable;

Thanks for your detail comment. This field confused me once.

Thanks to both for review! Will send v2.

[PATCH] KVM: nVMX: Fix some comment typos and coding style

[linmiaohe]

From: Miaohe Lin <linmiaohe@huawei.com>

Fix some typos in the comments. Also fix coding style.

Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
 arch/x86/include/asm/kvm_host.h | 2 +-
 arch/x86/kvm/vmx/nested.c       | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 4dffbc10d3f8..8196a4a0df8b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -782,7 +782,7 @@ struct kvm_vcpu_arch {
 
 	/*
 	 * Indicate whether the access faults on its page table in guest
-	 * which is set when fix page fault and used to detect unhandeable
+	 * which is set when fix page fault and used to detect unhandleable
 	 * instruction.
 	 */
 	bool write_fault_to_shadow_pgtable;
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 657c2eda357c..e7faebccd733 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -544,7 +544,8 @@ static void nested_vmx_disable_intercept_for_msr(unsigned long *msr_bitmap_l1,
 	}
 }
 
-static inline void enable_x2apic_msr_intercepts(unsigned long *msr_bitmap) {
+static inline void enable_x2apic_msr_intercepts(unsigned long *msr_bitmap)
+{
 	int msr;
 
 	for (msr = 0x800; msr <= 0x8ff; msr += BITS_PER_LONG) {
@@ -1981,7 +1982,7 @@ static int nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu,
 	}
 
 	/*
-	 * Clean fields data can't de used on VMLAUNCH and when we switch
+	 * Clean fields data can't be used on VMLAUNCH and when we switch
 	 * between different L2 guests as KVM keeps a single VMCS12 per L1.
 	 */
 	if (from_launch || evmcs_gpa_changed)
-- 
2.19.1

Re: [PATCH] KVM: nVMX: Fix some comment typos and coding style

[Vitaly Kuznetsov]

linmiaohe <linmiaohe@huawei.com> writes:

> From: Miaohe Lin <linmiaohe@huawei.com>
>
> Fix some typos in the comments. Also fix coding style.
>
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 2 +-
>  arch/x86/kvm/vmx/nested.c       | 5 +++--
>  2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 4dffbc10d3f8..8196a4a0df8b 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -782,7 +782,7 @@ struct kvm_vcpu_arch {
>  
>  	/*
>  	 * Indicate whether the access faults on its page table in guest

Indicates?

> -	 * which is set when fix page fault and used to detect unhandeable
> +	 * which is set when fix page fault and used to detect unhandleable
>  	 * instruction.

I have to admit that shadow MMU in KVM is not my strong side but this
comment reads weird, I'd appreciate if someone could suggest a better
alternative.

>  	 */
>  	bool write_fault_to_shadow_pgtable;
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 657c2eda357c..e7faebccd733 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -544,7 +544,8 @@ static void nested_vmx_disable_intercept_for_msr(unsigned long *msr_bitmap_l1,
>  	}
>  }
>  
> -static inline void enable_x2apic_msr_intercepts(unsigned long *msr_bitmap) {
> +static inline void enable_x2apic_msr_intercepts(unsigned long *msr_bitmap)
> +{
>  	int msr;
>  
>  	for (msr = 0x800; msr <= 0x8ff; msr += BITS_PER_LONG) {
> @@ -1981,7 +1982,7 @@ static int nested_vmx_handle_enlightened_vmptrld(struct kvm_vcpu *vcpu,
>  	}
>  
>  	/*
> -	 * Clean fields data can't de used on VMLAUNCH and when we switch
> +	 * Clean fields data can't be used on VMLAUNCH and when we switch

This one is even mine! :-)

>  	 * between different L2 guests as KVM keeps a single VMCS12 per L1.
>  	 */
>  	if (from_launch || evmcs_gpa_changed)

-- 
Vitaly

Re: [PATCH] KVM: nVMX: Fix some comment typos and coding style

[Sean Christopherson]

On Thu, Feb 06, 2020 at 12:32:38PM +0100, Vitaly Kuznetsov wrote:
> linmiaohe <linmiaohe@huawei.com> writes:
> 
> > From: Miaohe Lin <linmiaohe@huawei.com>
> >
> > Fix some typos in the comments. Also fix coding style.
> >
> > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> > ---
> >  arch/x86/include/asm/kvm_host.h | 2 +-
> >  arch/x86/kvm/vmx/nested.c       | 5 +++--
> >  2 files changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 4dffbc10d3f8..8196a4a0df8b 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -782,7 +782,7 @@ struct kvm_vcpu_arch {
> >  
> >  	/*
> >  	 * Indicate whether the access faults on its page table in guest
> 
> Indicates?
> 
> > -	 * which is set when fix page fault and used to detect unhandeable
> > +	 * which is set when fix page fault and used to detect unhandleable
> >  	 * instruction.
> 
> I have to admit that shadow MMU in KVM is not my strong side but this
> comment reads weird, I'd appreciate if someone could suggest a better
> alternative.

	/* One off flag for a stupid corner case in shadow paging. */
> 
> >  	 */

	/*
	 * Indicates the guest is trying to write a gfn that contains one or
	 * more of the PTEs used to translate the write itself, i.e. the access
	 * is changing its own translation in the guest page tables.  KVM exits
	 * to userspace if emulation of the faulting instruction fails and this
	 * flag is set, as KVM cannot make forward progress.
	 *
	 * If emulation fails for a write to guest page tables, KVM unprotects
	 * (zaps) the shadow page for the target gfn and resumes the guest to
	 * retry the non-emulatable instruction (on hardware).  Unprotecting the
	 * gfn doesn't allow forward progress for a self-changing access because
	 * doing so also zaps the translation for the gfn, i.e. retrying the
	 * instruction will hit a !PRESENT fault, which results in a new shadow
	 * page and sends KVM back to square one.
	 */
> >  	bool write_fault_to_shadow_pgtable;