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From: Joerg Roedel <joro@8bytes.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: x86@kernel.org, hpa@zytor.com, Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Hellstrom <thellstrom@vmware.com>,
	Jiri Slaby <jslaby@suse.cz>,
	Dan Williams <dan.j.williams@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Juergen Gross <jgross@suse.com>,
	Kees Cook <keescook@chromium.org>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	Joerg Roedel <jroedel@suse.de>
Subject: Re: [PATCH 08/62] x86/boot/compressed/64: Add IDT Infrastructure
Date: Sat, 15 Feb 2020 13:32:48 +0100
Message-ID: <20200215123248.GF22063@8bytes.org> (raw)
In-Reply-To: <87k14p5557.fsf@linux.intel.com>

On Fri, Feb 14, 2020 at 11:40:36AM -0800, Andi Kleen wrote:
> Joerg Roedel <joro@8bytes.org> writes:
> > +	addq    $8, %rsp
> > +
> > +	/*
> > +	 * Make sure we return to __KERNEL_CS - the CS selector on
> > +	 * the IRET frame might still be from an old BIOS GDT
> > +	 */
> > +	movq	$__KERNEL_CS, 8(%rsp)
> 
> This doesn't make sense. Either it's running on the correct CS
> before the exception or not. Likely there's some other problem
> here that you patched over with this hack.

It is actually a well-known situation and not some other problem. The
boot-code loaded a new GDT and IDT, but did not reload CS with a far
jump/ret/call. The CS value loaded is undefined and comes from the UEFI
BIOS. When an exception is raised, this old CS value is stored in the
IRET frame, and when IRET is executed the processor loads an undefined
CS value, which causes a triple fault with the current IDT setup.

The hack in this patch just fixes the IRET frame up so that it will
return to the correct CS. The reason for this hack was actually to safe
some instructions in the boot-path, because the space is limited there
between the defined offsets of the various entry points.

I removed this hack meanwhile and added a separate function which
reloads CS, DS, SS and ES and which is called from the boot-path, so
that there is no problem with the offsets.

Regards,

	Joerg

  reply index

Thread overview: 105+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 13:51 [RFC PATCH 00/62] Linux as SEV-ES Guest Support Joerg Roedel
2020-02-11 13:51 ` [PATCH 01/62] KVM: SVM: Add GHCB definitions Joerg Roedel
2020-02-11 13:51 ` [PATCH 02/62] KVM: SVM: Add GHCB Accessor functions Joerg Roedel
2020-02-11 13:51 ` [PATCH 03/62] x86/cpufeatures: Add SEV-ES CPU feature Joerg Roedel
2020-02-13  6:51   ` Borislav Petkov
2020-02-11 13:51 ` [PATCH 04/62] x86/traps: Move some definitions to <asm/trap_defs.h> Joerg Roedel
2020-02-11 13:51 ` [PATCH 05/62] x86/insn-decoder: Make inat-tables.c suitable for pre-decompression code Joerg Roedel
2020-02-11 13:52 ` [PATCH 06/62] x86/boot/compressed: Fix debug_puthex() parameter type Joerg Roedel
2020-02-11 13:52 ` [PATCH 07/62] x86/boot/compressed/64: Disable red-zone usage Joerg Roedel
2020-02-11 22:13   ` Andy Lutomirski
2020-02-11 13:52 ` [PATCH 08/62] x86/boot/compressed/64: Add IDT Infrastructure Joerg Roedel
2020-02-11 22:18   ` Andy Lutomirski
2020-02-12 11:19     ` Joerg Roedel
2020-02-14 19:40   ` Andi Kleen
2020-02-15 12:32     ` Joerg Roedel [this message]
2020-02-11 13:52 ` [PATCH 09/62] x86/boot/compressed/64: Rename kaslr_64.c to ident_map_64.c Joerg Roedel
2020-02-11 13:52 ` [PATCH 10/62] x86/boot/compressed/64: Add page-fault handler Joerg Roedel
2020-02-11 13:52 ` [PATCH 11/62] x86/boot/compressed/64: Always switch to own page-table Joerg Roedel
2020-02-11 13:52 ` [PATCH 12/62] x86/boot/compressed/64: Don't pre-map memory in KASLR code Joerg Roedel
2020-02-11 13:52 ` [PATCH 13/62] x86/boot/compressed/64: Change add_identity_map() to take start and end Joerg Roedel
2020-02-11 13:52 ` [PATCH 14/62] x86/boot/compressed/64: Add stage1 #VC handler Joerg Roedel
2020-02-11 22:23   ` Andy Lutomirski
2020-02-12 11:38     ` Joerg Roedel
2020-02-12 16:22       ` Andy Lutomirski
2020-02-11 13:52 ` [PATCH 15/62] x86/boot/compressed/64: Call set_sev_encryption_mask earlier Joerg Roedel
2020-02-11 13:52 ` [PATCH 16/62] x86/boot/compressed/64: Check return value of kernel_ident_mapping_init() Joerg Roedel
2020-02-11 13:52 ` [PATCH 17/62] x86/boot/compressed/64: Add function to map a page unencrypted Joerg Roedel
2020-02-11 13:52 ` [PATCH 18/62] x86/boot/compressed/64: Setup GHCB Based VC Exception handler Joerg Roedel
2020-02-11 22:25   ` Andy Lutomirski
2020-02-12 11:44     ` Joerg Roedel
2020-02-11 13:52 ` [PATCH 19/62] x86/sev-es: Add support for handling IOIO exceptions Joerg Roedel
2020-02-11 22:28   ` Andy Lutomirski
2020-02-12 11:49     ` Joerg Roedel
2020-02-11 13:52 ` [PATCH 20/62] x86/fpu: Move xgetbv()/xsetbv() into separate header Joerg Roedel
2020-02-11 13:52 ` [PATCH 21/62] x86/sev-es: Add CPUID handling to #VC handler Joerg Roedel
2020-02-11 13:52 ` [PATCH 22/62] x86/sev-es: Add handler for MMIO events Joerg Roedel
2020-02-11 13:52 ` [PATCH 23/62] x86/idt: Move IDT to data segment Joerg Roedel
2020-02-11 22:41   ` Andy Lutomirski
2020-02-12 11:55     ` Joerg Roedel
2020-02-12 16:23       ` Andy Lutomirski
2020-02-12 16:28         ` Jürgen Groß
2020-02-11 13:52 ` [PATCH 24/62] x86/idt: Split idt_data setup out of set_intr_gate() Joerg Roedel
2020-02-11 13:52 ` [PATCH 25/62] x86/head/64: Install boot GDT Joerg Roedel
2020-02-11 22:29   ` Andy Lutomirski
2020-02-12 12:20     ` Joerg Roedel
2020-02-11 13:52 ` [PATCH 26/62] x86/head/64: Reload GDT after switch to virtual addresses Joerg Roedel
2020-02-11 13:52 ` [PATCH 27/62] x86/head/64: Load segment registers earlier Joerg Roedel
2020-02-11 13:52 ` [PATCH 28/62] x86/head/64: Switch to initial stack earlier Joerg Roedel
2020-02-11 13:52 ` [PATCH 29/62] x86/head/64: Load IDT earlier Joerg Roedel
2020-02-11 13:52 ` [PATCH 30/62] x86/head/64: Move early exception dispatch to C code Joerg Roedel
2020-02-11 22:44   ` Andy Lutomirski
2020-02-12 12:39     ` Joerg Roedel
2020-02-11 13:52 ` [PATCH 31/62] x86/sev-es: Add SEV-ES Feature Detection Joerg Roedel
2020-02-11 13:52 ` [PATCH 32/62] x86/sev-es: Compile early handler code into kernel image Joerg Roedel
2020-02-11 13:52 ` [PATCH 33/62] x86/sev-es: Setup early #VC handler Joerg Roedel
2020-02-11 13:52 ` [PATCH 34/62] x86/sev-es: Setup GHCB based boot " Joerg Roedel
2020-02-11 13:52 ` [PATCH 35/62] x86/sev-es: Setup per-cpu GHCBs for the runtime handler Joerg Roedel
2020-02-11 22:46   ` Andy Lutomirski
2020-02-12 15:16     ` Joerg Roedel
2020-02-11 13:52 ` [PATCH 36/62] x86/sev-es: Add Runtime #VC Exception Handler Joerg Roedel
2020-02-11 13:52 ` [PATCH 37/62] x86/sev-es: Wire up existing #VC exit-code handlers Joerg Roedel
2020-02-11 13:52 ` [PATCH 38/62] x86/sev-es: Handle instruction fetches from user-space Joerg Roedel
2020-02-12 21:42   ` Andy Lutomirski
2020-02-11 13:52 ` [PATCH 39/62] x86/sev-es: Harden runtime #VC handler for exceptions " Joerg Roedel
2020-02-11 22:47   ` Andy Lutomirski
2020-02-12 13:16     ` Joerg Roedel
2020-02-11 13:52 ` [PATCH 40/62] x86/sev-es: Filter exceptions not supported " Joerg Roedel
2020-02-11 13:52 ` [PATCH 41/62] x86/sev-es: Handle MSR events Joerg Roedel
2020-02-13 15:45   ` Dave Hansen
2020-02-14  7:23     ` Joerg Roedel
2020-02-14 16:59       ` Dave Hansen
2020-02-15 12:45         ` Joerg Roedel
2020-02-11 13:52 ` [PATCH 42/62] x86/sev-es: Handle DR7 read/write events Joerg Roedel
2020-02-11 13:52 ` [PATCH 43/62] x86/sev-es: Handle WBINVD Events Joerg Roedel
2020-02-11 13:52 ` [PATCH 44/62] x86/sev-es: Handle RDTSC Events Joerg Roedel
2020-02-11 13:52 ` [PATCH 45/62] x86/sev-es: Handle RDPMC Events Joerg Roedel
2020-02-11 13:52 ` [PATCH 46/62] x86/sev-es: Handle INVD Events Joerg Roedel
2020-02-12  0:12   ` Andy Lutomirski
2020-02-12 15:36     ` Joerg Roedel
2020-02-11 13:52 ` [PATCH 47/62] x86/sev-es: Handle RDTSCP Events Joerg Roedel
2020-02-11 13:52 ` [PATCH 48/62] x86/sev-es: Handle MONITOR/MONITORX Events Joerg Roedel
2020-02-11 13:52 ` [PATCH 49/62] x86/sev-es: Handle MWAIT/MWAITX Events Joerg Roedel
2020-02-11 13:52 ` [PATCH 50/62] x86/sev-es: Handle VMMCALL Events Joerg Roedel
2020-02-12  0:14   ` Andy Lutomirski
2020-02-12 13:22     ` Joerg Roedel
2020-02-11 13:52 ` [PATCH 51/62] x86/sev-es: Handle #AC Events Joerg Roedel
2020-02-11 13:52 ` [PATCH 52/62] x86/sev-es: Handle #DB Events Joerg Roedel
2020-02-11 13:52 ` [PATCH 53/62] x86/paravirt: Allow hypervisor specific VMMCALL handling under SEV-ES Joerg Roedel
2020-02-11 13:52 ` [PATCH 54/62] x86/kvm: Add KVM " Joerg Roedel
2020-02-11 13:52 ` [PATCH 55/62] x86/vmware: Add VMware specific handling for VMMCALL " Joerg Roedel
2020-02-11 13:52 ` [PATCH 56/62] x86/realmode: Add SEV-ES specific trampoline entry point Joerg Roedel
2020-02-11 13:52 ` [PATCH 57/62] x86/realmode: Setup AP jump table Joerg Roedel
2020-02-11 13:52 ` [PATCH 58/62] x86/head/64: Don't call verify_cpu() on starting APs Joerg Roedel
2020-02-11 13:52 ` [PATCH 59/62] x86/head/64: Rename start_cpu0 Joerg Roedel
2020-02-11 13:52 ` [PATCH 60/62] x86/sev-es: Support CPU offline/online Joerg Roedel
2020-02-11 13:52 ` [PATCH 61/62] x86/cpufeature: Add SEV_ES_GUEST CPU Feature Joerg Roedel
2020-02-11 13:52 ` [PATCH 62/62] x86/sev-es: Add NMI state tracking Joerg Roedel
2020-02-11 22:50   ` Andy Lutomirski
2020-02-12 13:56     ` Joerg Roedel
2020-02-11 14:50 ` [RFC PATCH 00/62] Linux as SEV-ES Guest Support Peter Zijlstra
2020-02-11 15:43   ` Joerg Roedel
2020-02-11 22:12     ` Andy Lutomirski
2020-02-12 13:54       ` Joerg Roedel
2020-02-12  3:48 ` Andy Lutomirski
2020-02-12 13:59   ` Joerg Roedel

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