From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Graf Subject: Re: [Qemu-devel] [PATCH] KVM: Fix GSI number space limit Date: Fri, 06 Jun 2014 15:15:54 +0200 Message-ID: <5391BF0A.3000509@suse.de> References: <1402058765-48921-1-git-send-email-agraf@suse.de> <20140606151200.660e3072.cornelia.huck@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, kvm@vger.kernel.org To: Cornelia Huck Return-path: Received: from cantor2.suse.de ([195.135.220.15]:53008 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751774AbaFFNP5 (ORCPT ); Fri, 6 Jun 2014 09:15:57 -0400 In-Reply-To: <20140606151200.660e3072.cornelia.huck@de.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06.06.14 15:12, Cornelia Huck wrote: > On Fri, 6 Jun 2014 14:46:05 +0200 > Alexander Graf wrote: > >> KVM tells us the number of GSIs it can handle inside the kernel. That value is >> basically KVM_MAX_IRQ_ROUTES. However when we try to set the GSI mapping table, >> it checks for >> >> r = -EINVAL; >> if (routing.nr >= KVM_MAX_IRQ_ROUTES) >> goto out; >> >> erroring out even when we're only using all of the GSIs. To make sure we never >> hit that limit, let's reduce the number of GSIs we get from KVM by one. >> >> Signed-off-by: Alexander Graf >> --- >> kvm-all.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kvm-all.c b/kvm-all.c >> index 4e19eff..56a251b 100644 >> --- a/kvm-all.c >> +++ b/kvm-all.c >> @@ -938,7 +938,7 @@ void kvm_init_irq_routing(KVMState *s) >> { >> int gsi_count, i; >> >> - gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING); >> + gsi_count = kvm_check_extension(s, KVM_CAP_IRQ_ROUTING) - 1; >> if (gsi_count > 0) { >> unsigned int gsi_bits, i; >> > But gsi_count is already marked as used further down in this function, > isn't it? Confused. gsi_bits = ALIGN(gsi_count, 32); [...] for (i = gsi_count; i < gsi_bits; i++) { set_gsi(s, i); } So if you take gsi_count = 1024, what happens? gsi_count = 1024; gsi_bits = 1024; for (i = 1024; i < 1024; i++) { set_gsi(s, i); } At least in my world of C that loop never runs, no? Alex