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KVM: arm64: nv: Only toggle cache for virtual EL2 when SCTLR_EL2 changes 

So far we were flushing almost the entire universe whenever a VM would
load/unload the SCTLR_EL1 and the two versions of that register had
different MMU enabled settings.  This turned out to be so slow that it
prevented forward progress for a nested VM, because a scheduler timer
tick interrupt would always be pending when we reached the nested VM.

To avoid this problem, we consider the SCTLR_EL2 when evaluating if
caches are on or off when entering virtual EL2 (because this is the
value that we end up shadowing onto the hardware EL1 register).

Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230209175820.1939006-19-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
This commit is contained in:
Christoffer Dall 2023-02-09 17:58:20 +00:00 committed by Oliver Upton
parent 9f75b6d447
commit 191e0e1555
1 changed files with 10 additions and 1 deletions
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11
arch/arm64/include/asm/kvm_mmu.h
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@ -115,6 +115,7 @@ alternative_cb_end
#include <asm/cache.h> #include <asm/cache.h>
#include <asm/cacheflush.h> #include <asm/cacheflush.h>
#include <asm/mmu_context.h> #include <asm/mmu_context.h>
#include <asm/kvm_emulate.h>
#include <asm/kvm_host.h> #include <asm/kvm_host.h>
void kvm_update_va_mask(struct alt_instr *alt, void kvm_update_va_mask(struct alt_instr *alt,
@ -192,7 +193,15 @@ struct kvm;
static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu) static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu)
{ {
return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101; u64 cache_bits = SCTLR_ELx_M | SCTLR_ELx_C;
int reg;
if (vcpu_is_el2(vcpu))
reg = SCTLR_EL2;
else
reg = SCTLR_EL1;
return (vcpu_read_sys_reg(vcpu, reg) & cache_bits) == cache_bits;
} }
static inline void __clean_dcache_guest_page(void *va, size_t size) static inline void __clean_dcache_guest_page(void *va, size_t size)