Use the CAST instruction to swap the guest descriptor when FEAT_LSUI is enabled, avoiding the need to clear the PAN bit.
Signed-off-by: Yeoreum Yun <[email protected]> --- arch/arm64/kvm/at.c | 42 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 41 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c index 885bd5bb2f41..e49d2742a3ab 100644 --- a/arch/arm64/kvm/at.c +++ b/arch/arm64/kvm/at.c @@ -9,6 +9,7 @@ #include <asm/esr.h> #include <asm/kvm_hyp.h> #include <asm/kvm_mmu.h> +#include <asm/lsui.h> static void fail_s1_walk(struct s1_walk_result *wr, u8 fst, bool s1ptw) { @@ -1704,6 +1705,43 @@ int __kvm_find_s1_desc_level(struct kvm_vcpu *vcpu, u64 va, u64 ipa, int *level) } } +static int __lsui_swap_desc(u64 __user *ptep, u64 old, u64 new) +{ + u64 tmp = old; + int ret = 0; + + /* + * FEAT_LSUI is supported since Armv9.6, where FEAT_PAN is mandatory. + * However, this assumption may not always hold: + * + * - Some CPUs advertise FEAT_LSUI but lack FEAT_PAN. + * - Virtualisation or ID register overrides may expose invalid + * feature combinations. + * + * Rather than disabling FEAT_LSUI when FEAT_PAN is absent, wrap LSUI + * instructions with uaccess_ttbr0_enable()/disable() when + * ARM64_SW_TTBR0_PAN is enabled. + */ + uaccess_ttbr0_enable(); + + asm volatile(__LSUI_PREAMBLE + "1: cast %[old], %[new], %[addr]\n" + "2:\n" + _ASM_EXTABLE_UACCESS_ERR(1b, 2b, %w[ret]) + : [old] "+r" (old), [addr] "+Q" (*ptep), [ret] "+r" (ret) + : [new] "r" (new) + : "memory"); + + uaccess_ttbr0_disable(); + + if (ret) + return ret; + if (tmp != old) + return -EAGAIN; + + return ret; +} + static int __lse_swap_desc(u64 __user *ptep, u64 old, u64 new) { u64 tmp = old; @@ -1779,7 +1817,9 @@ int __kvm_at_swap_desc(struct kvm *kvm, gpa_t ipa, u64 old, u64 new) return -EPERM; ptep = (u64 __user *)hva + offset; - if (cpus_have_final_cap(ARM64_HAS_LSE_ATOMICS)) + if (cpus_have_final_cap(ARM64_HAS_LSUI)) + r = __lsui_swap_desc(ptep, old, new); + else if (cpus_have_final_cap(ARM64_HAS_LSE_ATOMICS)) r = __lse_swap_desc(ptep, old, new); else r = __llsc_swap_desc(ptep, old, new); -- LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}
