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Date: Fri, 23 Dec 2016 18:11:23 -0800 From: Andy Lutomirski <luto@...capital.net> To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> Cc: Ingo Molnar <mingo@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...e.de>, Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>, linux-msdos@...r.kernel.org, wine-devel@...ehq.org, Andrew Morton <akpm@...ux-foundation.org>, "H . Peter Anvin" <hpa@...or.com>, Brian Gerst <brgerst@...il.com>, Chen Yucong <slaoub@...il.com>, Chris Metcalf <cmetcalf@...lanox.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Fenghua Yu <fenghua.yu@...el.com>, Huang Rui <ray.huang@....com>, Jiri Slaby <jslaby@...e.cz>, Jonathan Corbet <corbet@....net>, "Michael S . Tsirkin" <mst@...hat.com>, Paul Gortmaker <paul.gortmaker@...driver.com>, "Ravi V . Shankar" <ravi.v.shankar@...el.com>, Shuah Khan <shuah@...nel.org>, Vlastimil Babka <vbabka@...e.cz>, Tony Luck <tony.luck@...el.com>, Paolo Bonzini <pbonzini@...hat.com>, "Liang Z . Li" <liang.z.li@...el.com>, Alexandre Julliard <julliard@...ehq.org>, Stas Sergeev <stsp@...t.ru> Subject: Re: [v2 6/7] x86/traps: Fixup general protection faults caused by UMIP On Fri, Dec 23, 2016 at 5:37 PM, Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> wrote: > If the User-Mode Instruction Prevention CPU feature is available and > enabled, a general protection fault will be issued if the instructions > sgdt, sldt, sidt, str or smsw are executed from user-mode context > (CPL > 0). If the fault was caused by any of the instructions protected > by UMIP, fixup_umip_exceptino will emulate dummy results for these > instructions. > > Cc: Andy Lutomirski <luto@...nel.org> > Cc: Andrew Morton <akpm@...ux-foundation.org> > Cc: H. Peter Anvin <hpa@...or.com> > Cc: Borislav Petkov <bp@...e.de> > Cc: Brian Gerst <brgerst@...il.com> > Cc: Chen Yucong <slaoub@...il.com> > Cc: Chris Metcalf <cmetcalf@...lanox.com> > Cc: Dave Hansen <dave.hansen@...ux.intel.com> > Cc: Fenghua Yu <fenghua.yu@...el.com> > Cc: Huang Rui <ray.huang@....com> > Cc: Jiri Slaby <jslaby@...e.cz> > Cc: Jonathan Corbet <corbet@....net> > Cc: Michael S. Tsirkin <mst@...hat.com> > Cc: Paul Gortmaker <paul.gortmaker@...driver.com> > Cc: Peter Zijlstra <peterz@...radead.org> > Cc: Ravi V. Shankar <ravi.v.shankar@...el.com> > Cc: Shuah Khan <shuah@...nel.org> > Cc: Vlastimil Babka <vbabka@...e.cz> > Cc: Tony Luck <tony.luck@...el.com> > Cc: Paolo Bonzini <pbonzini@...hat.com> > Cc: Liang Z. Li <liang.z.li@...el.com> > Cc: Alexandre Julliard <julliard@...ehq.org> > Cc: Stas Sergeev <stsp@...t.ru> > Cc: x86@...nel.org > Cc: linux-msdos@...r.kernel.org > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> > --- > arch/x86/kernel/traps.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index bf0c6d0..5044fb3 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -64,6 +64,7 @@ > #include <asm/trace/mpx.h> > #include <asm/mpx.h> > #include <asm/vm86.h> > +#include <asm/umip.h> > > #ifdef CONFIG_X86_64 > #include <asm/x86_init.h> > @@ -491,6 +492,9 @@ do_general_protection(struct pt_regs *regs, long error_code) > RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); > cond_local_irq_enable(regs); > > + if (user_mode(regs) && !fixup_umip_exception(regs)) > + return; > + I would do fixup_umip_exception(regs) == 0 to make it more obvious what's going on. Also, since you're allowing this in v8086 mode, I think this should have an explicit test in tools/testing/selftests/x86/entry_from_vm86.c. I *think* it will work fine, but the pt_regs handling in vm86 mode is quite scary and has been rewritten recently.
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