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 PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 23 Sep 2021 06:44:50 +0200 From: Juergen Gross <jgross@...e.com> To: Boris Ostrovsky <boris.ostrovsky@...cle.com>, xen-devel@...ts.xenproject.org, x86@...nel.org, linux-kernel@...r.kernel.org Cc: peterz@...radead.org, Stefano Stabellini <sstabellini@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com> Subject: Re: [PATCH v2 1/2] x86/xen: remove xen_have_vcpu_info_placement flag On 22.09.21 23:43, Boris Ostrovsky wrote: > > On 9/22/21 6:31 AM, Juergen Gross wrote: >> >> - if (xen_have_vcpu_info_placement) { >> - vcpup = &per_cpu(xen_vcpu_info, cpu); >> - info.mfn = arbitrary_virt_to_mfn(vcpup); >> - info.offset = offset_in_page(vcpup); >> + vcpup = &per_cpu(xen_vcpu_info, cpu); >> + info.mfn = arbitrary_virt_to_mfn(vcpup); >> + info.offset = offset_in_page(vcpup); >> >> - /* >> - * Check to see if the hypervisor will put the vcpu_info >> - * structure where we want it, which allows direct access via >> - * a percpu-variable. >> - * N.B. This hypercall can _only_ be called once per CPU. >> - * Subsequent calls will error out with -EINVAL. This is due to >> - * the fact that hypervisor has no unregister variant and this >> - * hypercall does not allow to over-write info.mfn and >> - * info.offset. >> - */ >> - err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, >> - xen_vcpu_nr(cpu), &info); >> - >> - if (err) { >> - pr_warn_once("register_vcpu_info failed: cpu=%d err=%d\n", >> - cpu, err); >> - xen_have_vcpu_info_placement = 0; >> - } else { >> - /* >> - * This cpu is using the registered vcpu info, even if >> - * later ones fail to. >> - */ >> - per_cpu(xen_vcpu, cpu) = vcpup; >> - } >> - } >> - >> - if (!xen_have_vcpu_info_placement) >> - xen_vcpu_info_reset(cpu); >> + /* >> + * N.B. This hypercall can _only_ be called once per CPU. >> + * Subsequent calls will error out with -EINVAL. This is due to >> + * the fact that hypervisor has no unregister variant and this >> + * hypercall does not allow to over-write info.mfn and >> + * info.offset. >> + */ >> + err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info, xen_vcpu_nr(cpu), >> + &info); >> + if (err) >> + panic("register_vcpu_info failed: cpu=%d err=%d\n", cpu, err); >> > > > This is change in behavior. Before if the hypercall failed we still try to boot. I am not sure we need to worry about this (since it's not clear it actually works) but I'd at least mention this in the commit message. Hmm, maybe I should have been more explicit saying that the hypercall was introduced in Xen 3.4, and only reason of failure is either an illegal vcpu, an invalid mapping specification, or a try to reissue the hypercall for a vcpu. None of those should ever happen. Juergen Download attachment "OpenPGP_0xB0DE9DD628BF132F.asc" of type "application/pgp-keys" (3092 bytes) Download attachment "OpenPGP_signature" of type "application/pgp-signature" (496 bytes)
Powered by blists - more mailing lists