Hi Marc, Christoffer,
On 10/12/2018 10:46, Marc Zyngier wrote:
> On 10/12/2018 10:19, Christoffer Dall wrote:
>> On Thu, Dec 06, 2018 at 05:31:25PM +0000, Marc Zyngier wrote:
>>> In order to avoid TLB corruption whilst invalidating TLBs on CPUs
>>> affected by erratum 1165522, we need to prevent S1 page tables
>>> from being usable.
>>>
>>> For this, we set the EL1 S1 MMU on, and also disable the page table
>>> walker (by setting the TCR_EL1.EPD* bits to 1).
>>>
>>> This ensures that once we switch to the EL1/EL0 translation regime,
>>> speculated AT instructions won't be able to parse the page tables.
>>> @@ -64,11 +93,18 @@ static void __hyp_text __tlb_switch_to_host_vhe(struct kvm *kvm,
>>> write_sysreg(0, vttbr_el2);
>>> write_sysreg(HCR_HOST_VHE_FLAGS, hcr_el2);
>>> isb();
>>> - local_irq_restore(flags);
>>> +
>>> + if (cpus_have_const_cap(ARM64_WORKAROUND_1165522)) {
>>> + /* Restore the guest's registers to what they were */
>>
>> host's ?
>
> Hum... Yes, silly thinko.
I thought these were the guests registers because they are EL1 registers and
this is a VHE-only path.
'interrupted guest' was how I read this. This stuff can get called if memory is
allocated for guest-A while a vcpu is loaded, and reclaims memory from guest-B
causing an mmu-notifier call for stage2. This is why we have to put guest-A's
registers back as we weren't pre-empted, and we expect EL1 to be untouched.
I agree they could belong to no-guest if a vcpu isn't loaded at all... is host
the term used here?
Thanks,
James
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