linux-kernel - Re: [PATCH v2 2/2] KVM: x86/mmu: Derive EPT violation RWX bits from EPTE RWX bits

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Date:   Fri, 8 Apr 2022 21:32:33 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Isaku Yamahata <isaku.yamahata@...il.com>
Cc:     SU Hang <darcy.sh@...group.com>, kvm@...r.kernel.org,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Kr???m?????? <rkrcmar@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] KVM: x86/mmu: Derive EPT violation RWX bits from
 EPTE RWX bits

On Fri, Apr 08, 2022, Isaku Yamahata wrote:
> On Tue, Mar 29, 2022 at 11:01:07AM +0800,
> SU Hang <darcy.sh@...group.com> wrote:
> 
> > From: Sean Christopherson <seanjc@...gle.com>
> > 
> > Derive the mask of RWX bits reported on EPT violations from the mask of
> > RWX bits that are shoved into EPT entries; the layout is the same, the
> > EPT violation bits are simply shifted by three.  Use the new shift and a
> > slight copy-paste of the mask derivation instead of completely open
> > coding the same to convert between the EPT entry bits and the exit
> > qualification when synthesizing a nested EPT Violation.
> > 
> > No functional change intended.
> > 
> > Cc: SU Hang <darcy.sh@...group.com>
> > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> > ---
> >  arch/x86/include/asm/vmx.h     | 7 +------
> >  arch/x86/kvm/mmu/paging_tmpl.h | 8 +++++++-
> >  arch/x86/kvm/vmx/vmx.c         | 4 +---
> >  3 files changed, 9 insertions(+), 10 deletions(-)
> > 
> > diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> > index 3586d4aeaac7..46bc7072f6a2 100644
> > --- a/arch/x86/include/asm/vmx.h
> > +++ b/arch/x86/include/asm/vmx.h
> > @@ -543,17 +543,12 @@ enum vm_entry_failure_code {
> >  #define EPT_VIOLATION_ACC_READ_BIT	0
> >  #define EPT_VIOLATION_ACC_WRITE_BIT	1
> >  #define EPT_VIOLATION_ACC_INSTR_BIT	2
> > -#define EPT_VIOLATION_READABLE_BIT	3
> > -#define EPT_VIOLATION_WRITABLE_BIT	4
> > -#define EPT_VIOLATION_EXECUTABLE_BIT	5
> >  #define EPT_VIOLATION_GVA_IS_VALID_BIT	7
> >  #define EPT_VIOLATION_GVA_TRANSLATED_BIT 8
> >  #define EPT_VIOLATION_ACC_READ		(1 << EPT_VIOLATION_ACC_READ_BIT)
> >  #define EPT_VIOLATION_ACC_WRITE		(1 << EPT_VIOLATION_ACC_WRITE_BIT)
> >  #define EPT_VIOLATION_ACC_INSTR		(1 << EPT_VIOLATION_ACC_INSTR_BIT)
> > -#define EPT_VIOLATION_READABLE		(1 << EPT_VIOLATION_READABLE_BIT)
> > -#define EPT_VIOLATION_WRITABLE		(1 << EPT_VIOLATION_WRITABLE_BIT)
> > -#define EPT_VIOLATION_EXECUTABLE	(1 << EPT_VIOLATION_EXECUTABLE_BIT)
> > +#define EPT_VIOLATION_RWX_MASK		(VMX_EPT_RWX_MASK << EPT_VIOLATION_RWX_SHIFT)
> 
> 
> "#define EPT_VIOLATION_RWX_SHIFT 3" is missing.
> It fails to compile.
> 
>   CC [M]  arch/x86/kvm/vmx/vmx.o
> In file included from linux/arch/x86/include/asm/virtext.h:18,
>                  from /linux/arch/x86/kvm/vmx/vmx.c:49:
> /linux/arch/x86/kvm/vmx/vmx.c: In function 'handle_ept_violation':
> /linux/arch/x86/include/asm/vmx.h:551:54: error: 'EPT_VIOLATION_RWX_SHIFT' undeclared (first use in this function); did you mean 'EPT_VIOLATION_RWX_MASK'?
>   551 | #define EPT_VIOLATION_RWX_MASK  (VMX_EPT_RWX_MASK << EPT_VIOLATION_RWX_SHIFT)
>       |                                                      ^~~~~~~~~~~~~~~~~~~~~~~

Yeah, not sure how that one line got dropped.

https://lore.kernel.org/all/20220408202815.386932-1-seanjc@google.com