From: james.morse@arm•com (James Morse)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH 03/11] KVM: arm64: Change hyp_panic()s dependency on tpidr_el2
Date: Thu, 08 Jun 2017 11:23:55 +0100 [thread overview]
Message-ID: <593925BB.30503@arm.com> (raw)
In-Reply-To: <20170606194525.GK9464@cbox>
Hi Christoffer,
On 06/06/17 20:45, Christoffer Dall wrote:
> On Mon, May 15, 2017 at 06:43:51PM +0100, James Morse wrote:
>> KVM calls hyp_panic() when anything unexpected happens. This may occur
>> while a guest owns the EL1 registers. KVM stashes the vcpu pointer in
>> tpidr_el2, which it uses to find the host context in order to restore
>> the host EL1 registers before parachuting into the host's panic().
>>
>> The host context is a struct kvm_cpu_context allocated in the per-cpu
>> area, and mapped to hyp. Given the per-cpu offset for this CPU, this is
>> easy to find. Change hyp_panic() to take a pointer to the
>> struct kvm_cpu_context. Wrap these calls with an asm function that
>> retrieves the struct kvm_cpu_context from the host's per-cpu area.
>>
>> Copy the per-cpu offset from the hosts tpidr_el1 into tpidr_el2 during
>> kvm init. (Later patches will make this unnecessary for VHE hosts)
>>
>> We print out the vcpu pointer as part of the panic message. Add a back
>> reference to the 'running vcpu' in the host cpu context to preserve this.
>> diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
>> index fce7cc507e0a..0f83e7e402ad 100644
>> --- a/arch/arm64/kvm/hyp/hyp-entry.S
>> +++ b/arch/arm64/kvm/hyp/hyp-entry.S
>> @@ -163,6 +163,13 @@ ENTRY(__hyp_do_panic)
>> eret
>> ENDPROC(__hyp_do_panic)
>>
>> +ENTRY(__hyp_panic)
>> + ldr x0, =kvm_host_cpu_state
>
> Why is this guaranteed to give us a valid EL2 address?
... it doesn't. Its a host address from the constant pool which is used by
hyp-panic as __host_ctxt:
> void __hyp_text __noreturn hyp_panic(struct kvm_cpu_context *__host_ctxt);
and fixed up with:
> host_ctxt = kern_hyp_va(__host_ctxt);
to give us the EL2 address before we access it.
For VHE the last step is a nop as the host address can be accessed directly.
I will add a comment here explaining this.
Thanks!
James
next prev parent reply other threads:[~2017-06-08 10:23 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-15 17:43 [PATCH 00/11] arm64/firmware: Software Delegated Exception Interface James Morse
2017-05-15 17:43 ` [PATCH 01/11] KVM: arm64: Store vcpu on the stack during __guest_enter() James Morse
2017-06-06 19:59 ` Christoffer Dall
2017-08-08 16:48 ` James Morse
2017-08-09 8:48 ` Christoffer Dall
2017-05-15 17:43 ` [PATCH 02/11] KVM: arm/arm64: Convert kvm_host_cpu_state to a static per-cpu allocation James Morse
2017-06-06 19:59 ` Christoffer Dall
2017-05-15 17:43 ` [PATCH 03/11] KVM: arm64: Change hyp_panic()s dependency on tpidr_el2 James Morse
2017-06-06 19:45 ` Christoffer Dall
2017-06-08 10:23 ` James Morse [this message]
2017-06-08 10:34 ` Christoffer Dall
2017-05-15 17:43 ` [PATCH 04/11] arm64: alternatives: use tpidr_el2 on VHE hosts James Morse
2017-05-15 17:43 ` [PATCH 05/11] arm64: KVM: Stop save/restoring host tpidr_el1 on VHE James Morse
2017-06-06 20:00 ` Christoffer Dall
2017-05-15 17:43 ` [PATCH 06/11] dt-bindings: add devicetree binding for describing arm64 SDEI firmware James Morse
2017-05-19 1:48 ` Rob Herring
2017-06-07 8:28 ` James Morse
2017-05-15 17:43 ` [PATCH 07/11] firmware: arm_sdei: Add driver for Software Delegated Exceptions James Morse
2017-07-19 13:52 ` Dave Martin
2017-08-08 16:48 ` James Morse
2017-05-15 17:43 ` [PATCH 08/11] arm64: kernel: Add arch-specific SDEI entry code and CPU masking James Morse
2017-05-15 17:43 ` [PATCH 09/11] firmware: arm_sdei: Add support for CPU and system power states James Morse
2017-05-15 17:43 ` [PATCH 10/11] firmware: arm_sdei: add support for CPU private events James Morse
2017-05-15 17:43 ` [PATCH 11/11] KVM: arm64: Delegate support for SDEI to userspace James Morse
2017-06-06 19:58 ` Christoffer Dall
2017-07-26 17:00 ` James Morse
2017-07-27 7:49 ` Christoffer Dall
2017-06-06 19:59 ` [PATCH 00/11] arm64/firmware: Software Delegated Exception Interface Christoffer Dall
2017-06-07 9:45 ` James Morse
2017-06-07 9:53 ` Christoffer Dall
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