From: Marc Zyngier <maz@kernel.org>
To: Jing Zhang <jingzhangos@google.com>
Cc: kernel-team@android.com,
Catalin Marinas <catalin.marinas@arm.com>,
Ard Biesheuvel <ardb@kernel.org>, Will Deacon <will@kernel.org>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 04/17] arm64: Provide an 'upgrade to VHE' stub hypercall
Date: Tue, 05 Jan 2021 08:24:21 +0000 [thread overview]
Message-ID: <2dad221aeef58d380d73c9768e430cd3@kernel.org> (raw)
In-Reply-To: <CAAdAUtgPCOfzKZZioMAG6KOY23MMnJdZ1Nsi5Z=0jHUbe2mbUw@mail.gmail.com>
On 2021-01-04 23:39, Jing Zhang wrote:
> On Mon, Dec 28, 2020 at 4:50 AM Marc Zyngier <maz@kernel.org> wrote:
>>
>> As we are about to change the way a VHE system boots, let's
>> provide the core helper, in the form of a stub hypercall that
>> enables VHE and replicates the full EL1 context at EL2, thanks
>> to EL1 and VHE-EL2 being extremely similar.
>>
>> On exception return, the kernel carries on at EL2. Fancy!
>>
>> Nothing calls this new hypercall yet, so no functional change.
>>
>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>> ---
>> arch/arm64/include/asm/virt.h | 7 +++-
>> arch/arm64/kernel/hyp-stub.S | 70
>> ++++++++++++++++++++++++++++++++++-
>> 2 files changed, 74 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/virt.h
>> b/arch/arm64/include/asm/virt.h
>> index ee6a48df89d9..7379f35ae2c6 100644
>> --- a/arch/arm64/include/asm/virt.h
>> +++ b/arch/arm64/include/asm/virt.h
>> @@ -35,8 +35,13 @@
>> */
>> #define HVC_RESET_VECTORS 2
>>
>> +/*
>> + * HVC_VHE_RESTART - Upgrade the CPU from EL1 to EL2, if possible
>> + */
>> +#define HVC_VHE_RESTART 3
>> +
>> /* Max number of HYP stub hypercalls */
>> -#define HVC_STUB_HCALL_NR 3
>> +#define HVC_STUB_HCALL_NR 4
>>
>> /* Error returned when an invalid stub number is passed into x0 */
>> #define HVC_STUB_ERR 0xbadca11
>> diff --git a/arch/arm64/kernel/hyp-stub.S
>> b/arch/arm64/kernel/hyp-stub.S
>> index 160f5881a0b7..6ffdc1f7778b 100644
>> --- a/arch/arm64/kernel/hyp-stub.S
>> +++ b/arch/arm64/kernel/hyp-stub.S
>> @@ -8,9 +8,9 @@
>>
>> #include <linux/init.h>
>> #include <linux/linkage.h>
>> -#include <linux/irqchip/arm-gic-v3.h>
>>
>> #include <asm/assembler.h>
>> +#include <asm/el2_setup.h>
>> #include <asm/kvm_arm.h>
>> #include <asm/kvm_asm.h>
>> #include <asm/ptrace.h>
>> @@ -47,10 +47,16 @@ SYM_CODE_END(__hyp_stub_vectors)
>>
>> SYM_CODE_START_LOCAL(el1_sync)
>> cmp x0, #HVC_SET_VECTORS
>> - b.ne 2f
>> + b.ne 1f
>> msr vbar_el2, x1
>> b 9f
>>
>> +1: cmp x0, #HVC_VHE_RESTART
>> + b.ne 2f
>> + mov x0, #HVC_SOFT_RESTART
>> + adr x1, mutate_to_vhe
>> + // fall through...
>> +
>> 2: cmp x0, #HVC_SOFT_RESTART
>> b.ne 3f
>> mov x0, x2
>> @@ -70,6 +76,66 @@ SYM_CODE_START_LOCAL(el1_sync)
>> eret
>> SYM_CODE_END(el1_sync)
>>
>> +// nVHE? No way! Give me the real thing!
>> +SYM_CODE_START_LOCAL(mutate_to_vhe)
>> + // Sanity check: MMU *must* be off
>> + mrs x0, sctlr_el2
>> + tbnz x0, #0, 1f
>> +
>> + // Needs to be VHE capable, obviously
>> + mrs x0, id_aa64mmfr1_el1
>> + ubfx x0, x0, #ID_AA64MMFR1_VHE_SHIFT, #4
>> + cbz x0, 1f
>> +
>> + // Engage the VHE magic!
>> + mov_q x0, HCR_HOST_VHE_FLAGS
>> + msr hcr_el2, x0
>> + isb
>> +
>> + // Doesn't do much on VHE, but still, worth a shot
>> + init_el2_state vhe
>> +
>> + // Use the EL1 allocated stack, per-cpu offset
>> + mrs x0, sp_el1
>> + mov sp, x0
>> + mrs x0, tpidr_el1
>> + msr tpidr_el2, x0
>> +
>> + // FP configuration, vectors
>> + mrs_s x0, SYS_CPACR_EL12
>> + msr cpacr_el1, x0
>> + mrs_s x0, SYS_VBAR_EL12
>> + msr vbar_el1, x0
>> +
>> + // Transfert the MM state from EL1 to EL2
>
> Transfert, typo?
Yes, thanks.
If you are going to review this, may I suggest you look at v2 [1]
instead? The initial version had so many issues that I'm trying
to pretend it never happened.
Cheers,
M.
[1] https://lore.kernel.org/r/20210104135011.2063104-1-maz@kernel.org
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2021-01-05 8:24 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-28 10:49 [PATCH 00/17] arm64: Early CPU feature override, and an application to VHE Marc Zyngier
2020-12-28 10:49 ` [PATCH 01/17] arm64: Fix labels in el2_setup macros Marc Zyngier
2020-12-28 10:49 ` [PATCH 02/17] arm64: Fix outdated TCR setup comment Marc Zyngier
2020-12-28 10:49 ` [PATCH 03/17] arm64: Turn the MMU-on sequence into a macro Marc Zyngier
2020-12-28 10:49 ` [PATCH 04/17] arm64: Provide an 'upgrade to VHE' stub hypercall Marc Zyngier
2021-01-04 23:39 ` Jing Zhang
2021-01-05 8:24 ` Marc Zyngier [this message]
2020-12-28 10:49 ` [PATCH 05/17] arm64: Initialise as nVHE before switching to VHE Marc Zyngier
2020-12-28 10:49 ` [PATCH 06/17] arm64: Move VHE-specific SPE setup to mutate_to_vhe() Marc Zyngier
2020-12-28 10:49 ` [PATCH 07/17] arm64: Simplify init_el2_state to be non-VHE only Marc Zyngier
2020-12-28 10:49 ` [PATCH 08/17] arm64: Move SCTLR_EL1 initialisation to EL-agnostic code Marc Zyngier
2020-12-28 10:49 ` [PATCH 09/17] arm64: cpufeature: Add global feature override facility Marc Zyngier
2020-12-28 10:49 ` [PATCH 10/17] arm64: Extract early FDT mapping from kaslr_early_init() Marc Zyngier
2020-12-28 10:49 ` [PATCH 11/17] arm64: cpufeature: Add an early command-line cpufeature override facility Marc Zyngier
2020-12-28 10:49 ` [PATCH 12/17] arm64: Allow ID_AA64MMFR1_EL1.VH to be overridden from the command line Marc Zyngier
2020-12-28 10:49 ` [PATCH 13/17] arm64: Honor VHE being disabled from the command-line Marc Zyngier
2020-12-28 10:49 ` [PATCH 14/17] arm64: Add an aliasing facility for the idreg override Marc Zyngier
2020-12-28 10:49 ` [PATCH 15/17] arm64: Make kvm-arm.mode={nvhe, protected} an alias of id_aa64mmfr1.vh=0 Marc Zyngier
2020-12-28 10:49 ` [PATCH 16/17] KVM: arm64: Document HVC_VHE_RESTART stub hypercall Marc Zyngier
2020-12-28 10:49 ` [PATCH 17/17] arm64: Move "nokaslr" over to the early cpufeature infrastructure Marc Zyngier
2020-12-29 19:27 ` [PATCH 00/17] arm64: Early CPU feature override, and an application to VHE Marc Zyngier
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