diff options
Diffstat (limited to 'arch/arm64/include/asm/el2_setup.h')
| -rw-r--r-- | arch/arm64/include/asm/el2_setup.h | 38 |
1 files changed, 32 insertions, 6 deletions
diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h index b37da3ee8529..99a7c0235e6d 100644 --- a/arch/arm64/include/asm/el2_setup.h +++ b/arch/arm64/include/asm/el2_setup.h @@ -24,22 +24,48 @@ * ID_AA64MMFR4_EL1.E2H0 < 0. On such CPUs HCR_EL2.E2H is RES1, but it * can reset into an UNKNOWN state and might not read as 1 until it has * been initialized explicitly. - * - * Fruity CPUs seem to have HCR_EL2.E2H set to RAO/WI, but - * don't advertise it (they predate this relaxation). - * * Initalize HCR_EL2.E2H so that later code can rely upon HCR_EL2.E2H * indicating whether the CPU is running in E2H mode. */ mrs_s x1, SYS_ID_AA64MMFR4_EL1 sbfx x1, x1, #ID_AA64MMFR4_EL1_E2H0_SHIFT, #ID_AA64MMFR4_EL1_E2H0_WIDTH cmp x1, #0 - b.ge .LnVHE_\@ + b.lt .LnE2H0_\@ + /* + * Unfortunately, HCR_EL2.E2H can be RES1 even if not advertised + * as such via ID_AA64MMFR4_EL1.E2H0: + * + * - Fruity CPUs predate the !FEAT_E2H0 relaxation, and seem to + * have HCR_EL2.E2H implemented as RAO/WI. + * + * - On CPUs that lack FEAT_FGT, a hypervisor can't trap guest + * reads of ID_AA64MMFR4_EL1 to advertise !FEAT_E2H0. NV + * guests on these hosts can write to HCR_EL2.E2H without + * trapping to the hypervisor, but these writes have no + * functional effect. + * + * Handle both cases by checking for an essential VHE property + * (system register remapping) to decide whether we're + * effectively VHE-only or not. + */ + msr_hcr_el2 x0 // Setup HCR_EL2 as nVHE + isb + mov x1, #1 // Write something to FAR_EL1 + msr far_el1, x1 + isb + mov x1, #2 // Try to overwrite it via FAR_EL2 + msr far_el2, x1 + isb + mrs x1, far_el1 // If we see the latest write in FAR_EL1, + cmp x1, #2 // we can safely assume we are VHE only. + b.ne .LnVHE_\@ // Otherwise, we know that nVHE works. + +.LnE2H0_\@: orr x0, x0, #HCR_E2H -.LnVHE_\@: msr_hcr_el2 x0 isb +.LnVHE_\@: .endm .macro __init_el2_sctlr |