Messages in this thread Patch in this message | | | Date | Fri, 17 Mar 2023 14:25:26 +0000 | From | Catalin Marinas <> | Subject | Re: [PATCH 01/10] KVM: arm64: initialize HCRX_EL2 |
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On Thu, Feb 16, 2023 at 04:00:03PM +0000, Kristina Martsenko wrote: > ARMv8.7/9.2 adds a new hypervisor configuration register HCRX_EL2. > Initialize the register to a safe value (all fields 0), to be robust > against firmware that has not initialized it.
I think the risk of firmware not initialising this register is small given that EL3 needs to set SCR_EL3.HXEn to allow EL2 access. But it doesn't hurt to re-initialise it in the hypervisor.
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > index 212d93aca5e6..e06b34322339 100644 > --- a/arch/arm64/kernel/head.S > +++ b/arch/arm64/kernel/head.S > @@ -572,6 +572,13 @@ SYM_INNER_LABEL(init_el2, SYM_L_LOCAL) > msr hcr_el2, x0 > isb > > + mrs x0, ID_AA64MMFR1_EL1 > + ubfx x0, x0, #ID_AA64MMFR1_EL1_HCX_SHIFT, #4 > + cbz x0, 3f > + mov_q x1, HCRX_HOST_FLAGS > + msr_s SYS_HCRX_EL2, x1 > + isb > +3: > init_el2_state
Nitpick: we can probably leave a single ISB after both HCR_EL2 and HCRX_EL2 are initialised. Well, we could probably drop all of them altogether, there's at least one down this path.
> > /* Hypervisor stub */ > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S > index a6d67c2bb5ae..01f854697c70 100644 > --- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S > @@ -95,6 +95,12 @@ SYM_CODE_START_LOCAL(___kvm_hyp_init) > ldr x1, [x0, #NVHE_INIT_HCR_EL2] > msr hcr_el2, x1 > > + mrs x1, ID_AA64MMFR1_EL1 > + ubfx x1, x1, #ID_AA64MMFR1_EL1_HCX_SHIFT, #4 > + cbz x1, 1f > + mov_q x2, HCRX_HOST_FLAGS > + msr_s SYS_HCRX_EL2, x2 > +1:
Maybe you could use a macro to avoid writing this sequence twice. I lost track of the KVM initialisation refactoring since pKVM, it looks like the other register values are loaded from a structure here. I guess a value of 0 doesn't make sense to store (unless at a later point it becomes non-zero).
-- Catalin
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