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From: Peter Zijlstra <peterz@infradead.org>
To: Joerg Roedel <jroedel@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>, Joerg Roedel <joro@8bytes.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Tom Lendacky <Thomas.Lendacky@amd.com>,
	Mike Stunes <mstunes@vmware.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	"H. Peter Anvin" <hpa@zytor.com>, Juergen Gross <JGross@suse.com>,
	Jiri Slaby <jslaby@suse.cz>, Kees Cook <keescook@chromium.org>,
	kvm list <kvm@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Thomas Hellstrom <thellstrom@vmware.com>,
	Linux Virtualization <virtualization@lists.linux-foundation.org>,
	X86 ML <x86@kernel.org>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: Should SEV-ES #VC use IST? (Re: [PATCH] Allow RDTSC and RDTSCP from userspace)
Date: Tue, 23 Jun 2020 17:16:07 +0200	[thread overview]
Message-ID: <20200623151607.GJ4817@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200623144940.GE14101@suse.de>

On Tue, Jun 23, 2020 at 04:49:40PM +0200, Joerg Roedel wrote:
> > We're talking about the 3rd case where the only reason things 'work' is
> > because we'll have to panic():
> > 
> >  - #MC
> 
> Okay, #MC is special and can only be handled on a best-effort basis, as
> #MC could happen anytime, also while already executing the #MC handler.

I think the hardware has a MCE-mask bit somewhere. Flaky though because
clearing it isn't 'atomic' with IRET, so there's a 'funny' window.

It also interacts really bad with the NMI handler. If we get an #MC
early in the NMI, where we hard-rely on the NMI-mask being set to set-up
the recursion stack, then the #MC IRET will clear the NMI-mask, and
we're toast.

Andy has wild and crazy ideas, but I don't think we need more crazy
here.

#VC SNP has a similar problem vs NMI, that needs to die() irrespective
of the #VC IST recursion.

> >  - #DB with BUS LOCK DEBUG EXCEPTION
> 
> If I understand the problem correctly, this can be solved by moving off
> the IST stack to the current task stack in the #DB handler, like I plan
> to do for #VC, no?

Hmm, probably. Would take a bit of care, but should be doable.

> >  - #VC SNP
> 
> This has to panic for other reasons that can't be worked around. It
> boils down to detecting that the HV is doing something fishy and bail
> out to avoid further harm (like in the #MC handler).

Right, but it doesn't take away that IST-any-time vectors are
fundamentally screwy.

Both the MCE and NMI have masks that are, as per the above, differently
funny, but the other ISTs do not. Also, even if they had masks, the
interaction between them is still screwy.

#VC would've been so much better if it would've had a mask bit
somewhere, then at least we could've had the exception entry covered.
Another #VC with the mask set should probably result in #DF or Shutdown,
but that's all water under the bridge I suspect.




  reply	other threads:[~2020-06-23 15:16 UTC|newest]

Thread overview: 181+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-19  9:12 [RFC PATCH 00/70 v2] x86: SEV-ES Guest Support Joerg Roedel
2020-03-19  9:12 ` [PATCH 01/70] KVM: SVM: Add GHCB definitions Joerg Roedel
2020-03-23 13:23   ` [PATCH] KVM: SVM: Use __packed shorthard Borislav Petkov
2020-03-24 12:43     ` Joerg Roedel
2020-03-19  9:12 ` [PATCH 02/70] KVM: SVM: Add GHCB Accessor functions Joerg Roedel
2020-03-19  9:13 ` [PATCH 03/70] x86/cpufeatures: Add SEV-ES CPU feature Joerg Roedel
2020-03-19  9:13 ` [PATCH 04/70] x86/traps: Move some definitions to <asm/trap_defs.h> Joerg Roedel
2020-03-19  9:13 ` [PATCH 05/70] x86/insn: Make inat-tables.c suitable for pre-decompression code Joerg Roedel
2020-03-25 15:39   ` Borislav Petkov
2020-03-27  3:02     ` Masami Hiramatsu
2020-04-16 15:24       ` Joerg Roedel
2020-04-17 12:50         ` Masami Hiramatsu
2020-04-17 13:39           ` Joerg Roedel
2020-03-19  9:13 ` [PATCH 06/70] x86/umip: Factor out instruction fetch Joerg Roedel
2020-03-26 17:21   ` Borislav Petkov
2020-03-19  9:13 ` [PATCH 07/70] x86/umip: Factor out instruction decoding Joerg Roedel
2020-03-26 17:24   ` Borislav Petkov
2020-03-19  9:13 ` [PATCH 08/70] x86/insn: Add insn_get_modrm_reg_off() Joerg Roedel
2020-03-27  3:57   ` Masami Hiramatsu
2020-03-19  9:13 ` [PATCH 09/70] x86/insn: Add insn_rep_prefix() helper Joerg Roedel
2020-03-27  3:56   ` Masami Hiramatsu
2020-03-19  9:13 ` [PATCH 10/70] x86/boot/compressed: Fix debug_puthex() parameter type Joerg Roedel
2020-03-28 11:23   ` [tip: x86/boot] " tip-bot2 for Joerg Roedel
2020-03-19  9:13 ` [PATCH 11/70] x86/boot/compressed/64: Disable red-zone usage Joerg Roedel
2020-03-31 13:16   ` Borislav Petkov
2020-03-19  9:13 ` [PATCH 12/70] x86/boot/compressed/64: Add IDT Infrastructure Joerg Roedel
2020-04-07  2:21   ` Arvind Sankar
2020-04-16 13:30     ` Joerg Roedel
2020-03-19  9:13 ` [PATCH 13/70] x86/boot/compressed/64: Rename kaslr_64.c to ident_map_64.c Joerg Roedel
2020-03-19  9:13 ` [PATCH 14/70] x86/boot/compressed/64: Add page-fault handler Joerg Roedel
2020-04-02 11:49   ` Borislav Petkov
2020-03-19  9:13 ` [PATCH 15/70] x86/boot/compressed/64: Always switch to own page-table Joerg Roedel
2020-04-06 11:56   ` Borislav Petkov
2020-03-19  9:13 ` [PATCH 16/70] x86/boot/compressed/64: Don't pre-map memory in KASLR code Joerg Roedel
2020-03-19  9:13 ` [PATCH 17/70] x86/boot/compressed/64: Change add_identity_map() to take start and end Joerg Roedel
2020-03-19  9:13 ` [PATCH 18/70] x86/boot/compressed/64: Add stage1 #VC handler Joerg Roedel
2020-03-20 21:16   ` David Rientjes
2020-03-20 22:19     ` Joerg Roedel
2020-04-06 12:41   ` Borislav Petkov
2020-03-19  9:13 ` [PATCH 19/70] x86/boot/compressed/64: Call set_sev_encryption_mask earlier Joerg Roedel
2020-03-19  9:13 ` [PATCH 20/70] x86/boot/compressed/64: Check return value of kernel_ident_mapping_init() Joerg Roedel
2020-03-19  9:13 ` [PATCH 21/70] x86/boot/compressed/64: Add function to map a page unencrypted Joerg Roedel
2020-03-20 20:53   ` David Rientjes
2020-03-20 21:02     ` Dave Hansen
2020-03-20 22:12       ` Joerg Roedel
2020-03-20 22:26         ` Dave Hansen
2020-03-21 15:40           ` Joerg Roedel
2020-03-19  9:13 ` [PATCH 22/70] x86/boot/compressed/64: Setup GHCB Based VC Exception handler Joerg Roedel
2020-03-19  9:13 ` [PATCH 23/70] x86/sev-es: Add support for handling IOIO exceptions Joerg Roedel
2020-03-20 21:03   ` David Rientjes
2020-03-20 22:24     ` Joerg Roedel
2020-03-19  9:13 ` [PATCH 24/70] x86/fpu: Move xgetbv()/xsetbv() into separate header Joerg Roedel
2020-03-19  9:13 ` [PATCH 25/70] x86/sev-es: Add CPUID handling to #VC handler Joerg Roedel
2020-03-19  9:13 ` [PATCH 26/70] x86/idt: Move IDT to data segment Joerg Roedel
2020-03-19  9:13 ` [PATCH 27/70] x86/idt: Split idt_data setup out of set_intr_gate() Joerg Roedel
2020-03-19  9:13 ` [PATCH 28/70] x86/idt: Move two function from k/idt.c to i/a/desc.h Joerg Roedel
2020-03-19  9:13 ` [PATCH 29/70] x86/head/64: Install boot GDT Joerg Roedel
2020-03-19  9:13 ` [PATCH 30/70] x86/head/64: Reload GDT after switch to virtual addresses Joerg Roedel
2020-03-19  9:13 ` [PATCH 31/70] x86/head/64: Load segment registers earlier Joerg Roedel
2020-03-19  9:13 ` [PATCH 32/70] x86/head/64: Switch to initial stack earlier Joerg Roedel
2020-03-19  9:13 ` [PATCH 33/70] x86/head/64: Build k/head64.c with -fno-stack-protector Joerg Roedel
2020-03-19  9:13 ` [PATCH 34/70] x86/head/64: Load IDT earlier Joerg Roedel
2020-03-19  9:13 ` [PATCH 35/70] x86/head/64: Move early exception dispatch to C code Joerg Roedel
2020-03-19  9:13 ` [PATCH 36/70] x86/sev-es: Add SEV-ES Feature Detection Joerg Roedel
2020-03-19  9:13 ` [PATCH 37/70] x86/sev-es: Compile early handler code into kernel image Joerg Roedel
2020-03-19  9:13 ` [PATCH 38/70] x86/sev-es: Setup early #VC handler Joerg Roedel
2020-03-19  9:13 ` [PATCH 39/70] x86/sev-es: Setup GHCB based boot " Joerg Roedel
2020-03-19  9:13 ` [PATCH 40/70] x86/sev-es: Setup per-cpu GHCBs for the runtime handler Joerg Roedel
2020-04-14 19:03   ` Mike Stunes
2020-04-14 20:04     ` Tom Lendacky
2020-04-14 20:12       ` Dave Hansen
2020-04-14 20:16         ` Tom Lendacky
2020-04-14 20:18           ` Tom Lendacky
2020-04-15 15:54       ` Joerg Roedel
2020-04-15 15:53     ` Joerg Roedel
2020-04-23  1:33       ` Bo Gan
2020-04-23 11:30         ` Joerg Roedel
2020-03-19  9:13 ` [PATCH 41/70] x86/sev-es: Add Runtime #VC Exception Handler Joerg Roedel
2020-03-19 15:44   ` Andy Lutomirski
2020-03-19 16:24     ` Joerg Roedel
2020-03-19 18:43       ` Andy Lutomirski
2020-03-19 19:38         ` Joerg Roedel
2020-03-19  9:13 ` [PATCH 42/70] x86/sev-es: Support nested #VC exceptions Joerg Roedel
2020-03-19 15:46   ` Andy Lutomirski
2020-03-19 16:12     ` Joerg Roedel
2020-03-19  9:13 ` [PATCH 43/70] x86/sev-es: Wire up existing #VC exit-code handlers Joerg Roedel
2020-03-19  9:13 ` [PATCH 44/70] x86/sev-es: Handle instruction fetches from user-space Joerg Roedel
2020-03-19  9:13 ` [PATCH 45/70] x86/sev-es: Harden runtime #VC handler for exceptions " Joerg Roedel
2020-03-19  9:13 ` [PATCH 46/70] x86/sev-es: Filter exceptions not supported " Joerg Roedel
2020-03-19  9:13 ` [PATCH 47/70] x86/sev-es: Handle MMIO events Joerg Roedel
2020-03-19  9:13 ` [PATCH 48/70] x86/sev-es: Handle MMIO String Instructions Joerg Roedel
2020-03-19  9:13 ` [PATCH 49/70] x86/sev-es: Handle MSR events Joerg Roedel
2020-03-19  9:13 ` [PATCH 50/70] x86/sev-es: Handle DR7 read/write events Joerg Roedel
2020-03-19  9:13 ` [PATCH 51/70] x86/sev-es: Handle WBINVD Events Joerg Roedel
2020-03-19  9:13 ` [PATCH 52/70] x86/sev-es: Handle RDTSC Events Joerg Roedel
2020-03-19  9:13 ` [PATCH 53/70] x86/sev-es: Handle RDPMC Events Joerg Roedel
2020-03-19  9:13 ` [PATCH 54/70] x86/sev-es: Handle INVD Events Joerg Roedel
2020-03-19  9:13 ` [PATCH 55/70] x86/sev-es: Handle RDTSCP Events Joerg Roedel
2020-04-24 21:03   ` [PATCH] Allow RDTSC and RDTSCP from userspace Mike Stunes
2020-04-24 21:24     ` Dave Hansen
2020-04-24 21:27       ` Tom Lendacky
2020-04-24 22:53         ` Dave Hansen
2020-04-25 12:49           ` Joerg Roedel
2020-04-25 18:15             ` Andy Lutomirski
2020-04-25 19:10               ` Joerg Roedel
2020-04-25 19:47                 ` Andy Lutomirski
2020-04-25 20:23                   ` Joerg Roedel
2020-04-25 22:10                     ` Andy Lutomirski
2020-04-27 17:37                       ` Should SEV-ES #VC use IST? (Re: [PATCH] Allow RDTSC and RDTSCP from userspace) Andy Lutomirski
2020-04-27 18:15                         ` Andrew Cooper
2020-04-27 18:43                         ` Tom Lendacky
2020-04-28  7:55                         ` Joerg Roedel
2020-04-28 16:34                           ` Andrew Cooper
2020-06-23 11:07                           ` Peter Zijlstra
2020-06-23 11:30                             ` Joerg Roedel
2020-06-23 11:48                               ` Peter Zijlstra
2020-06-23 12:04                                 ` Joerg Roedel
2020-06-23 12:52                                   ` Peter Zijlstra
2020-06-23 13:40                                     ` Joerg Roedel
2020-06-23 13:59                                       ` Peter Zijlstra
2020-06-23 14:53                                         ` Peter Zijlstra
2020-06-23 14:59                                           ` Joerg Roedel
2020-06-23 15:23                                             ` Peter Zijlstra
2020-06-23 15:38                                               ` Peter Zijlstra
2020-06-23 15:38                                               ` Joerg Roedel
2020-06-23 16:02                                                 ` Peter Zijlstra
2020-06-23 15:39                                               ` Andrew Cooper
2020-06-23 15:52                                                 ` Peter Zijlstra
2020-06-23 16:03                                                   ` Dave Hansen
2020-06-23 16:13                                                     ` Peter Zijlstra
2020-06-23 16:13                                                 ` Borislav Petkov
2020-06-23 11:51                               ` Andrew Cooper
2020-06-23 12:47                                 ` Peter Zijlstra
2020-06-23 13:57                                   ` Andrew Cooper
2020-06-23 15:51                                 ` Borislav Petkov
2020-06-23  9:45                         ` Joerg Roedel
2020-06-23 10:45                           ` Peter Zijlstra
2020-06-23 11:11                             ` Joerg Roedel
2020-06-23 11:14                               ` Peter Zijlstra
2020-06-23 11:43                                 ` Joerg Roedel
2020-06-23 11:50                                   ` Peter Zijlstra
2020-06-23 12:12                                     ` Joerg Roedel
2020-06-23 13:03                                       ` Peter Zijlstra
2020-06-23 14:49                                         ` Joerg Roedel
2020-06-23 15:16                                           ` Peter Zijlstra [this message]
2020-06-23 15:32                                             ` Andrew Cooper
2020-06-23 16:10                                               ` Borislav Petkov
2020-06-23 15:22                                         ` Andrew Cooper
2020-06-23 18:26                                           ` Andy Lutomirski
2020-06-23 18:56                                             ` Andrew Cooper
2020-04-27 18:47             ` [PATCH] Allow RDTSC and RDTSCP from userspace Dave Hansen
2020-04-25 12:28     ` Joerg Roedel
2020-03-19  9:13 ` [PATCH 56/70] x86/sev-es: Handle MONITOR/MONITORX Events Joerg Roedel
2020-03-19  9:13 ` [PATCH 57/70] x86/sev-es: Handle MWAIT/MWAITX Events Joerg Roedel
2020-03-19  9:13 ` [PATCH 58/70] x86/sev-es: Handle VMMCALL Events Joerg Roedel
2020-03-19  9:13 ` [PATCH 59/70] x86/sev-es: Handle #AC Events Joerg Roedel
2020-03-19  9:13 ` [PATCH 60/70] x86/sev-es: Handle #DB Events Joerg Roedel
2020-03-19  9:13 ` [PATCH 61/70] x86/paravirt: Allow hypervisor specific VMMCALL handling under SEV-ES Joerg Roedel
2020-03-19  9:13 ` [PATCH 62/70] x86/kvm: Add KVM " Joerg Roedel
2020-03-20 21:23   ` David Rientjes
2020-03-20 22:21     ` Joerg Roedel
2020-03-19  9:14 ` [PATCH 63/70] x86/vmware: Add VMware specific handling for VMMCALL " Joerg Roedel
2020-03-19 10:18   ` Thomas Hellstrom
2020-03-19  9:14 ` [PATCH 64/70] x86/realmode: Add SEV-ES specific trampoline entry point Joerg Roedel
2020-03-19  9:14 ` [PATCH 65/70] x86/realmode: Setup AP jump table Joerg Roedel
2020-03-19  9:14 ` [PATCH 66/70] x86/head/64: Don't call verify_cpu() on starting APs Joerg Roedel
2020-03-19  9:14 ` [PATCH 67/70] x86/head/64: Rename start_cpu0 Joerg Roedel
2020-03-19  9:14 ` [PATCH 68/70] x86/sev-es: Support CPU offline/online Joerg Roedel
2020-03-19  9:14 ` [PATCH 69/70] x86/cpufeature: Add SEV_ES_GUEST CPU Feature Joerg Roedel
2020-03-19  9:14 ` [PATCH 70/70] x86/sev-es: Add NMI state tracking Joerg Roedel
2020-03-19 15:35   ` Andy Lutomirski
2020-03-19 16:07     ` Joerg Roedel
2020-03-19 18:40       ` Andy Lutomirski
2020-03-19 19:26         ` Joerg Roedel
2020-03-19 21:27           ` Andy Lutomirski
2020-03-20 19:48             ` Joerg Roedel
2020-03-20 13:17     ` [RFC PATCH v2.1] x86/sev-es: Handle NMI State Joerg Roedel
2020-03-20 14:42       ` Dave Hansen
2020-03-20 19:42         ` Joerg Roedel
2020-03-19 16:53   ` [PATCH 70/70] x86/sev-es: Add NMI state tracking Mika Penttilä
2020-03-19 19:41     ` Joerg Roedel

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