From: Will Deacon <will@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE"
<devicetree@vger.kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
Android KVM <android-kvm@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
open list <linux-kernel@vger.kernel.org>,
Rob Herring <robh+dt@kernel.org>, Fuad Tabba <tabba@google.com>,
Marc Zyngier <maz@kernel.org>,
kernel-team@android.com,
"open list:KERNEL VIRTUAL MACHINE FOR ARM64 \(KVM/arm64\)"
<kvmarm@lists.cs.columbia.edu>,
"moderated list:ARM64 PORT \(AARCH64 ARCHITECTURE\)"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH 16/27] KVM: arm64: Prepare Hyp memory protection
Date: Mon, 7 Dec 2020 11:10:14 +0000 [thread overview]
Message-ID: <20201207111013.GA4379@willie-the-truck> (raw)
In-Reply-To: <20201207110528.GA18365@C02TD0UTHF1T.local>
On Mon, Dec 07, 2020 at 11:05:45AM +0000, Mark Rutland wrote:
> On Mon, Dec 07, 2020 at 10:20:03AM +0000, Will Deacon wrote:
> > On Fri, Dec 04, 2020 at 06:01:52PM +0000, Quentin Perret wrote:
> > > On Thursday 03 Dec 2020 at 12:57:33 (+0000), Fuad Tabba wrote:
> > > <snip>
> > > > > +SYM_FUNC_START(__kvm_init_switch_pgd)
> > > > > + /* Turn the MMU off */
> > > > > + pre_disable_mmu_workaround
> > > > > + mrs x2, sctlr_el2
> > > > > + bic x3, x2, #SCTLR_ELx_M
> > > > > + msr sctlr_el2, x3
> > > > > + isb
> > > > > +
> > > > > + tlbi alle2
> > > > > +
> > > > > + /* Install the new pgtables */
> > > > > + ldr x3, [x0, #NVHE_INIT_PGD_PA]
> > > > > + phys_to_ttbr x4, x3
> > > > > +alternative_if ARM64_HAS_CNP
> > > > > + orr x4, x4, #TTBR_CNP_BIT
> > > > > +alternative_else_nop_endif
> > > > > + msr ttbr0_el2, x4
> > > > > +
> > > > > + /* Set the new stack pointer */
> > > > > + ldr x0, [x0, #NVHE_INIT_STACK_HYP_VA]
> > > > > + mov sp, x0
> > > > > +
> > > > > + /* And turn the MMU back on! */
> > > > > + dsb nsh
> > > > > + isb
> > > > > + msr sctlr_el2, x2
> > > > > + isb
> > > > > + ret x1
> > > > > +SYM_FUNC_END(__kvm_init_switch_pgd)
> > > > > +
> > > >
> > > > Should the instruction cache be flushed here (ic iallu), to discard
> > > > speculatively fetched instructions?
> > >
> > > Hmm, Will? Thoughts?
> >
> > The I-cache is physically tagged, so not sure what invalidation would
> > achieve here. Fuad -- what do you think could go wrong specifically?
>
> While the MMU is off, instruction fetches can be made from the PoC
> rather than the PoU, so where instructions have been modified/copied and
> not cleaned to the PoC, it's possible to fetch stale copies into the
> I-caches. The physical tag doesn't prevent that.
Oh yeah, we even have a comment about that in
idmap_kpti_install_ng_mappings(). Maybe we should wrap disable_mmu and
enable_mmu in some macros so we don't have to trip over this every time (and
this would mean we could get rid of pre_disable_mmu_workaround too).
> In the regular CPU boot paths, __enabble_mmu() has an IC IALLU after
> enabling the MMU to ensure that we get rid of anything stale (e.g. so
> secondaries don't miss ftrace patching, which is only cleaned to the
> PoU).
>
> That might not be a problem here, if things are suitably padded and
> never dynamically patched, but if so it's probably worth a comment.
It's fragile enough that we should just do the invalidation.
Will
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next prev parent reply other threads:[~2020-12-07 11:10 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-17 18:15 [RFC PATCH 00/27] KVM/arm64: A stage 2 for the host Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 01/27] arm64: lib: Annotate {clear, copy}_page() as position-independent Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 02/27] KVM: arm64: Link position-independent string routines into .hyp.text Quentin Perret
2020-11-23 12:34 ` David Brazdil
2020-11-23 14:06 ` Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 03/27] KVM: arm64: Add standalone ticket spinlock implementation for use at hyp Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 04/27] KVM: arm64: Initialize kvm_nvhe_init_params early Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 05/27] KVM: arm64: Avoid free_page() in page-table allocator Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 06/27] KVM: arm64: Factor memory allocation out of pgtable.c Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 07/27] KVM: arm64: Introduce a BSS section for use at Hyp Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 08/27] KVM: arm64: Make kvm_call_hyp() a function call " Quentin Perret
2020-11-23 12:51 ` David Brazdil
2020-11-17 18:15 ` [RFC PATCH 09/27] KVM: arm64: Allow using kvm_nvhe_sym() in hyp code Quentin Perret
2020-11-23 12:57 ` David Brazdil
2020-11-23 14:02 ` Quentin Perret
2020-11-23 14:54 ` David Brazdil
2020-11-17 18:15 ` [RFC PATCH 10/27] KVM: arm64: Introduce an early Hyp page allocator Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 11/27] KVM: arm64: Stub CONFIG_DEBUG_LIST at Hyp Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 12/27] KVM: arm64: Introduce a Hyp buddy page allocator Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 13/27] KVM: arm64: Enable access to sanitized CPU features at EL2 Quentin Perret
2020-11-23 10:55 ` Fuad Tabba
2020-11-23 13:51 ` Quentin Perret
2020-11-23 13:22 ` David Brazdil
2020-11-23 14:39 ` Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 14/27] KVM: arm64: Factor out vector address calculation Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 15/27] of/fdt: Introduce early_init_dt_add_memory_hyp() Quentin Perret
2020-11-17 19:44 ` Rob Herring
2020-11-18 9:25 ` Quentin Perret
2020-11-18 14:31 ` Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 16/27] KVM: arm64: Prepare Hyp memory protection Quentin Perret
2020-12-03 12:57 ` Fuad Tabba
2020-12-04 18:01 ` Quentin Perret
2020-12-07 10:20 ` Will Deacon
2020-12-07 11:05 ` Mark Rutland
2020-12-07 11:10 ` Will Deacon [this message]
2020-12-07 11:14 ` Fuad Tabba
2020-12-07 11:16 ` Fuad Tabba
2020-12-07 11:58 ` Quentin Perret
2020-12-07 13:54 ` Marc Zyngier
2020-12-07 14:17 ` Quentin Perret
2020-12-07 13:40 ` Will Deacon
2020-12-07 14:11 ` Quentin Perret
2020-12-08 9:40 ` Will Deacon
2020-11-17 18:15 ` [RFC PATCH 17/27] KVM: arm64: Elevate Hyp mappings creation at EL2 Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 18/27] KVM: arm64: Use kvm_arch for stage 2 pgtable Quentin Perret
2020-11-17 18:15 ` [RFC PATCH 19/27] KVM: arm64: Use kvm_arch in kvm_s2_mmu Quentin Perret
2020-11-17 18:16 ` [RFC PATCH 20/27] KVM: arm64: Set host stage 2 using kvm_nvhe_init_params Quentin Perret
2020-11-17 18:16 ` [RFC PATCH 21/27] KVM: arm64: Refactor kvm_arm_setup_stage2() Quentin Perret
2020-11-17 18:16 ` [RFC PATCH 22/27] KVM: arm64: Refactor __load_guest_stage2() Quentin Perret
2020-11-17 18:16 ` [RFC PATCH 23/27] KVM: arm64: Refactor __populate_fault_info() Quentin Perret
2020-11-17 18:16 ` [RFC PATCH 24/27] KVM: arm64: Make memcache anonymous in pgtable allocator Quentin Perret
2020-11-17 18:16 ` [RFC PATCH 25/27] KVM: arm64: Reserve memory for host stage 2 Quentin Perret
2020-11-17 18:16 ` [RFC PATCH 26/27] KVM: arm64: Sort the memblock regions list Quentin Perret
2020-11-17 18:16 ` [RFC PATCH 27/27] KVM: arm64: Wrap the host with a stage 2 Quentin Perret
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