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Message-ID: <CALCETrV4JqVfHQhz4EuFKfHXK=zABsmwZpgz4ijz89O8v4GdfA@mail.gmail.com> Date: Mon, 20 Feb 2017 08:56:35 -0800 From: Andy Lutomirski <luto@...capital.net> To: Thomas Garnier <thgarnie@...gle.com> Cc: Jim Mattson <jmattson@...gle.com>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>, Andrey Ryabinin <aryabinin@...tuozzo.com>, Alexander Potapenko <glider@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, Kees Cook <keescook@...omium.org>, Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de>, Paul Gortmaker <paul.gortmaker@...driver.com>, "Rafael J . Wysocki" <rjw@...ysocki.net>, Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>, Jiri Kosina <jikos@...nel.org>, Matt Fleming <matt@...eblueprint.co.uk>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, Juergen Gross <jgross@...e.com>, Rusty Russell <rusty@...tcorp.com.au>, Peter Zijlstra <peterz@...radead.org>, Christian Borntraeger <borntraeger@...ibm.com>, "Luis R . Rodriguez" <mcgrof@...nel.org>, He Chen <he.chen@...ux.intel.com>, Brian Gerst <brgerst@...il.com>, Stanislaw Gruszka <sgruszka@...hat.com>, Arnd Bergmann <arnd@...db.de>, Adam Buchbinder <adam.buchbinder@...il.com>, Dave Hansen <dave.hansen@...el.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Josh Poimboeuf <jpoimboe@...hat.com>, Tim Chen <tim.c.chen@...ux.intel.com>, Rik van Riel <riel@...hat.com>, Andi Kleen <ak@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>, Michael Ellerman <mpe@...erman.id.au>, Joerg Roedel <joro@...tes.org>, Paolo Bonzini <pbonzini@...hat.com>, Radim Krčmář <rkrcmar@...hat.com>, "the arch/x86 maintainers" <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>, kasan-dev <kasan-dev@...glegroups.com>, Linux PM list <linux-pm@...r.kernel.org>, "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>, "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>, lguest@...ts.ozlabs.org, kvm list <kvm@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH v3 4/4] KVM: VMX: Simplify segment_base On Fri, Feb 17, 2017 at 2:01 PM, Thomas Garnier <thgarnie@...gle.com> wrote: > On Fri, Feb 17, 2017 at 1:00 PM, Jim Mattson <jmattson@...gle.com> wrote: >> On Fri, Feb 17, 2017 at 12:11 PM, Thomas Garnier <thgarnie@...gle.com> wrote: >>> On Fri, Feb 17, 2017 at 9:49 AM, Jim Mattson <jmattson@...gle.com> wrote: >>>> >>>> Can we use the read-only GDT here? When expanding the virtual address >>>> for 64-bit system descriptors, isn't it sufficient to check (d->s == 0 >>>> && d->type != 0)? >>> >>> We can use the readonly GDT but I think doesn't matter one or the >>> other here. We have to check specific types for LDT or TSS, other >>> values describe other entries (cf Intel volume 3, 3.5) (for example 14 >>> & 15 on 64-bits are for trap & interrupt gates). >> >> According to volume 3 of the SDM, section 3.5.2: >> >> The following system descriptors expand to 16 bytes: >> — Call gate descriptors (see Section 5.8.3.1, “IA-32e Mode Call Gates”) >> — IDT gate descriptors (see Section 6.14.1, “64-Bit Mode IDT”) >> — LDT and TSS descriptors (see Section 7.2.3, “TSS Descriptor in 64-bit mode”). >> >> All legal system descriptor types (except for 0: Upper 8 bytes of an 16-byte >> descriptor) should get the high 32 bits of the base address from the next 8-byte >> descriptor. >> > > Ok, then I will test an updated version next week. > I'm going to send out some preliminary patches that just get rid of this problem entirely.
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