KVM: arm64: Don't set HCR_EL2.TVM when S2FWB is supported
On CPUs that support S2FWB (Armv8.4+), KVM configures the stage 2 page
tables to override the memory attributes of memory accesses, regardless
of the stage 1 page table configurations, and also when the stage 1 MMU
is turned off. This results in all memory accesses to RAM being
cacheable, including during early boot of the guest.
On CPUs without this feature, memory accesses were non-cacheable during
boot until the guest turned on the stage 1 MMU, and we had to detect
when the guest turned on the MMU, such that we could invalidate all cache
entries and ensure a consistent view of memory with the MMU turned on.
When the guest turned on the caches, we would call stage2_flush_vm()
from kvm_toggle_cache().
However, stage2_flush_vm() walks all the stage 2 tables, and calls
__kvm_flush-dcache_pte, which on a system with S2FWB does ... absolutely
nothing.
We can avoid that whole song and dance, and simply not set TVM when
creating a VM on a system that has S2FWB.
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20191028130541.30536-1-christoffer.dall@arm.com
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index ddf9d76..6e5d839 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -61,7 +61,6 @@
* RW: 64bit by default, can be overridden for 32bit VMs
* TAC: Trap ACTLR
* TSC: Trap SMC
- * TVM: Trap VM ops (until M+C set in SCTLR_EL1)
* TSW: Trap cache operations by set/way
* TWE: Trap WFE
* TWI: Trap WFI
@@ -74,7 +73,7 @@
* SWIO: Turn set/way invalidates into set/way clean+invalidate
*/
#define HCR_GUEST_FLAGS (HCR_TSC | HCR_TSW | HCR_TWE | HCR_TWI | HCR_VM | \
- HCR_TVM | HCR_BSU_IS | HCR_FB | HCR_TAC | \
+ HCR_BSU_IS | HCR_FB | HCR_TAC | \
HCR_AMO | HCR_SWIO | HCR_TIDCP | HCR_RW | HCR_TLOR | \
HCR_FMO | HCR_IMO)
#define HCR_VIRT_EXCP_MASK (HCR_VSE | HCR_VI | HCR_VF)