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[34.168.104.7]) by smtp.gmail.com with ESMTPSA id mm7-20020a17090b358700b002191e769546sm1603599pjb.4.2022.12.16.08.34.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Dec 2022 08:34:54 -0800 (PST) Date: Fri, 16 Dec 2022 16:34:50 +0000 From: Sean Christopherson To: Yu Zhang Cc: kvm@vger.kernel.org, pbonzini@redhat.com, maz@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com, suzuki.poulose@arm.com, oliver.upton@linux.dev, catalin.marinas@arm.com, will@kernel.org, dwmw2@infradead.org, paul@xen.org Subject: Re: [PATCH v4 1/2] KVM: MMU: Introduce 'INVALID_GFN' and use it for GFN values Message-ID: References: <20221216085928.1671901-1-yu.c.zhang@linux.intel.com> <20221216085928.1671901-2-yu.c.zhang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221216085928.1671901-2-yu.c.zhang@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, Dec 16, 2022, Yu Zhang wrote: > Currently, KVM xen and its shared info selftest code uses > 'GPA_INVALID' for GFN values, but actually it is more accurate > to use the name 'INVALID_GFN'. So just add a new definition > and use it. > > No functional changes intended. > > Suggested-by: David Woodhouse > Signed-off-by: Yu Zhang > --- > arch/x86/kvm/xen.c | 4 ++-- > include/linux/kvm_types.h | 1 + > tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c | 4 ++-- > 3 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c > index d7af40240248..6908a74ab303 100644 > --- a/arch/x86/kvm/xen.c > +++ b/arch/x86/kvm/xen.c > @@ -41,7 +41,7 @@ static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn) > int ret = 0; > int idx = srcu_read_lock(&kvm->srcu); > > - if (gfn == GPA_INVALID) { > + if (gfn == INVALID_GFN) { Grrr! This magic value is ABI, as "gfn == -1" yields different behavior than a random, garbage gfn. So, sadly, we can't simply introduce INVALID_GFN here, and instead need to do something like: diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 20522d4ba1e0..2d31caaf812c 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1766,6 +1766,7 @@ struct kvm_xen_hvm_attr { __u8 vector; __u8 runstate_update_flag; struct { +#define KVM_XEN_INVALID_GFN (~0ull) __u64 gfn; } shared_info; struct { > kvm_gpc_deactivate(gpc); > goto out; > }