linux-kernel - Re: [PATCH v2 02/10] KVM: define common __KVM_GUESTDBG_USE_SW/HW

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20150414082448.GR6186@cbox>
Date:	Tue, 14 Apr 2015 10:24:48 +0200
From:	Christoffer Dall <christoffer.dall@...aro.org>
To:	Alex Bennée <alex.bennee@...aro.org>
Cc:	kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.cs.columbia.edu, marc.zyngier@....com,
	peter.maydell@...aro.org, agraf@...e.de, drjones@...hat.com,
	pbonzini@...hat.com, zhichao.huang@...aro.org,
	jan.kiszka@...mens.com, dahi@...ux.vnet.ibm.com,
	r65777@...escale.com, bp@...e.de,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"maintainer:X86 ARCHITECTURE..." <x86@...nel.org>,
	Gleb Natapov <gleb@...nel.org>,
	Bharat Bhushan <Bharat.Bhushan@...escale.com>,
	Alexey Kardashevskiy <aik@...abs.ru>,
	Mihai Caraman <mihai.caraman@...escale.com>,
	Nadav Amit <namit@...technion.ac.il>,
	"open list:LINUX FOR POWERPC..." <linuxppc-dev@...ts.ozlabs.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:ABI/API" <linux-api@...r.kernel.org>
Subject: Re: [PATCH v2 02/10] KVM: define common __KVM_GUESTDBG_USE_SW/HW_BP
 values

On Mon, Apr 13, 2015 at 03:51:33PM +0100, Alex Bennée wrote:
> 
> Christoffer Dall <christoffer.dall@...aro.org> writes:
> 
> > On Tue, Mar 31, 2015 at 04:08:00PM +0100, Alex Bennée wrote:
> >> Currently x86, powerpc and soon arm64 use the same two architecture
> >> specific bits for guest debug support for software and hardware
> >> breakpoints. This makes the shared values explicit while leaving the
> >> gate open for another architecture to use some other value if they
> >> really really want to.
> >> 
> >> Signed-off-by: Alex Bennée <alex.bennee@...aro.org>
> >> 
> >> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
> >> index ab4d473..1731569 100644
> >> --- a/arch/powerpc/include/uapi/asm/kvm.h
> >> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> >> @@ -310,8 +310,8 @@ struct kvm_guest_debug_arch {
> >>   * and upper 16 bits are architecture specific. Architecture specific defines
> >>   * that ioctl is for setting hardware breakpoint or software breakpoint.
> >>   */
> >> -#define KVM_GUESTDBG_USE_SW_BP		0x00010000
> >> -#define KVM_GUESTDBG_USE_HW_BP		0x00020000
> >> +#define KVM_GUESTDBG_USE_SW_BP		__KVM_GUESTDBG_USE_SW_BP
> >> +#define KVM_GUESTDBG_USE_HW_BP		__KVM_GUESTDBG_USE_HW_BP
> >>  
> >>  /* definition of registers in kvm_run */
> >>  struct kvm_sync_regs {
> >> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> >> index d7dcef5..1438202 100644
> >> --- a/arch/x86/include/uapi/asm/kvm.h
> >> +++ b/arch/x86/include/uapi/asm/kvm.h
> >> @@ -250,8 +250,8 @@ struct kvm_debug_exit_arch {
> >>  	__u64 dr7;
> >>  };
> >>  
> >> -#define KVM_GUESTDBG_USE_SW_BP		0x00010000
> >> -#define KVM_GUESTDBG_USE_HW_BP		0x00020000
> >> +#define KVM_GUESTDBG_USE_SW_BP		__KVM_GUESTDBG_USE_SW_BP
> >> +#define KVM_GUESTDBG_USE_HW_BP		__KVM_GUESTDBG_USE_HW_BP
> >>  #define KVM_GUESTDBG_INJECT_DB		0x00040000
> >>  #define KVM_GUESTDBG_INJECT_BP		0x00080000
> >>  
> >> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> >> index 5eedf84..ce2db14 100644
> >> --- a/include/uapi/linux/kvm.h
> >> +++ b/include/uapi/linux/kvm.h
> >> @@ -525,8 +525,16 @@ struct kvm_s390_irq {
> >>  
> >>  /* for KVM_SET_GUEST_DEBUG */
> >>  
> >> -#define KVM_GUESTDBG_ENABLE		0x00000001
> >> -#define KVM_GUESTDBG_SINGLESTEP		0x00000002
> >> +#define KVM_GUESTDBG_ENABLE		(1 << 0)
> >> +#define KVM_GUESTDBG_SINGLESTEP	(1 << 1)
> >> +
> >> +/*
> >> + * Architecture specific stuff uses the top 16 bits of the field,
> >
> > can you be more specific than 'stuff' here?  features?
> >
> >> + * however there is some shared commonality for the common cases
> >
> > I don't like this sentence; shared commonality is a pleonasm and the use
> > of however makes it sounds like there's some caveat here.
> 
> OK I can see that - after I looked it up ;-)
> 
> > If the top 16 bits are indeed arhictecture specific, then I think they
> > should just be defined in their architecture specific headers.  Unless
> > the idea here is that there's a fixed set of of flags that architectures
> > can choose to support, in which case it should simply be defined in the
> > common header.
> 
> Well an architecture might not support some features and want to use
> those bits for something else? I didn't want to force the bottom two
> of the architecture specific bits to wasted if the features don't exist.
> 
In that case I think the definition is local to each architecture and
should indeed just be duplicated.  The __ definitions complicate more
than they help as they are exported to userspace etc.  The KVM
maintainers may have a different view on this though.

-Christoffer
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/