Hi Marc,
On Tue, Aug 8, 2023 at 4:47 AM Marc Zyngier <maz@xxxxxxxxxx> wrote:
>
> Fine Grained Traps are fun. Not.
>
> Implement the fine grained trap forwarding, reusing the Coarse Grained
> Traps infrastructure previously implemented.
>
> Each sysreg/instruction inserted in the xarray gets a FGT group
> (vaguely equivalent to a register number), a bit number in that register,
> and a polarity.
>
> It is then pretty easy to check the FGT state at handling time, just
> like we do for the coarse version (it is just faster).
>
> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> arch/arm64/kvm/emulate-nested.c | 78 ++++++++++++++++++++++++++++++++-
> 1 file changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> index cd0544c3577e..af75c2775638 100644
> --- a/arch/arm64/kvm/emulate-nested.c
> +++ b/arch/arm64/kvm/emulate-nested.c
> @@ -928,6 +928,27 @@ static const struct encoding_to_trap_config encoding_to_cgt[] __initconst = {
>
> static DEFINE_XARRAY(sr_forward_xa);
>
> +enum fgt_group_id {
> + __NO_FGT_GROUP__,
> +
> + /* Must be last */
> + __NR_FGT_GROUP_IDS__
> +};
> +
> +#define SR_FGT(sr, g, b, p) \
> + { \
> + .encoding = sr, \
> + .end = sr, \
> + .tc = { \
> + .fgt = g ## _GROUP, \
> + .bit = g ## _EL2_ ## b ## _SHIFT, \
> + .pol = p, \
> + }, \
> + }
> +
> +static const struct encoding_to_trap_config encoding_to_fgt[] __initconst = {
> +};
> +
> static union trap_config get_trap_config(u32 sysreg)
> {
> return (union trap_config) {
> @@ -941,6 +962,7 @@ int __init populate_nv_trap_config(void)
>
> BUILD_BUG_ON(sizeof(union trap_config) != sizeof(void *));
> BUILD_BUG_ON(__NR_TRAP_GROUP_IDS__ > BIT(TC_CGT_BITS));
> + BUILD_BUG_ON(__NR_FGT_GROUP_IDS__ > BIT(TC_FGT_BITS));
>
> for (int i = 0; i < ARRAY_SIZE(encoding_to_cgt); i++) {
> const struct encoding_to_trap_config *cgt = &encoding_to_cgt[i];
> @@ -963,6 +985,34 @@ int __init populate_nv_trap_config(void)
> kvm_info("nv: %ld coarse grained trap handlers\n",
> ARRAY_SIZE(encoding_to_cgt));
>
> + if (!cpus_have_final_cap(ARM64_HAS_FGT))
> + goto check_mcb;
> +
> + for (int i = 0; i < ARRAY_SIZE(encoding_to_fgt); i++) {
> + const struct encoding_to_trap_config *fgt = &encoding_to_fgt[i];
> + union trap_config tc;
> +
> + tc = get_trap_config(fgt->encoding);
> +
> + if (tc.fgt) {
> + kvm_err("Duplicate FGT for (%d, %d, %d, %d, %d)\n",
> + sys_reg_Op0(fgt->encoding),
> + sys_reg_Op1(fgt->encoding),
> + sys_reg_CRn(fgt->encoding),
> + sys_reg_CRm(fgt->encoding),
> + sys_reg_Op2(fgt->encoding));
> + ret = -EINVAL;
> + }
> +
> + tc.val |= fgt->tc.val;
> + xa_store(&sr_forward_xa, fgt->encoding,
> + xa_mk_value(tc.val), GFP_KERNEL);
> + }
> +
> + kvm_info("nv: %ld fine grained trap handlers\n",
> + ARRAY_SIZE(encoding_to_fgt));
> +
> +check_mcb:
> for (int id = __MULTIPLE_CONTROL_BITS__;
> id < (__COMPLEX_CONDITIONS__ - 1);
> id++) {
> @@ -1031,13 +1081,26 @@ static enum trap_behaviour compute_trap_behaviour(struct kvm_vcpu *vcpu,
> return __do_compute_trap_behaviour(vcpu, tc.cgt, b);
> }
>
> +static bool check_fgt_bit(u64 val, const union trap_config tc)
> +{
> + return ((val >> tc.bit) & 1) == tc.pol;
> +}
> +
> +#define sanitised_sys_reg(vcpu, reg) \
> + ({ \
> + u64 __val; \
> + __val = __vcpu_sys_reg(vcpu, reg); \
> + __val &= ~__ ## reg ## _RES0; \
> + (__val); \
> + })
> +
> bool __check_nv_sr_forward(struct kvm_vcpu *vcpu)
> {
> union trap_config tc;
> enum trap_behaviour b;
> bool is_read;
> u32 sysreg;
> - u64 esr;
> + u64 esr, val;
>
> if (!vcpu_has_nv(vcpu) || is_hyp_ctxt(vcpu))
> return false;
> @@ -1060,6 +1123,19 @@ bool __check_nv_sr_forward(struct kvm_vcpu *vcpu)
> if (!tc.val)
> return false;
>
> + switch ((enum fgt_group_id)tc.fgt) {
> + case __NO_FGT_GROUP__:
> + break;
> +
> + case __NR_FGT_GROUP_IDS__:
> + /* Something is really wrong, bail out */
> + WARN_ONCE(1, "__NR_FGT_GROUP_IDS__");
> + return false;
Do we need a default clause here to catch unexpected tc.fgt values?
> + }
> +
> + if (tc.fgt != __NO_FGT_GROUP__ && check_fgt_bit(val, tc))
> + goto inject;
> +
> b = compute_trap_behaviour(vcpu, tc);
>
> if (((b & BEHAVE_FORWARD_READ) && is_read) ||
> --
> 2.34.1
>
>
Thanks,
Jing
