Hi Marc,
On Mon, Jul 08, 2024 at 05:57:58PM +0100, Marc Zyngier wrote:
> In order to plug the brokenness of our current AT implementation,
> we need a SW walker that is going to... err.. walk the S1 tables
> and tell us what it finds.
>
> Of course, it builds on top of our S2 walker, and share similar
> concepts. The beauty of it is that since it uses kvm_read_guest(),
> it is able to bring back pages that have been otherwise evicted.
>
> This is then plugged in the two AT S1 emulation functions as
> a "slow path" fallback. I'm not sure it is that slow, but hey.
>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> arch/arm64/kvm/at.c | 538 ++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 520 insertions(+), 18 deletions(-)
>
> diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
> index 71e3390b43b4c..8452273cbff6d 100644
> --- a/arch/arm64/kvm/at.c
> +++ b/arch/arm64/kvm/at.c
> @@ -4,9 +4,305 @@
> * Author: Jintack Lim <jintack.lim@xxxxxxxxxx>
> */
>
> +#include <linux/kvm_host.h>
> +
> +#include <asm/esr.h>
> #include <asm/kvm_hyp.h>
> #include <asm/kvm_mmu.h>
>
> +struct s1_walk_info {
> + u64 baddr;
> + unsigned int max_oa_bits;
> + unsigned int pgshift;
> + unsigned int txsz;
> + int sl;
> + bool hpd;
> + bool be;
> + bool nvhe;
> + bool s2;
> +};
> +
> +struct s1_walk_result {
> + union {
> + struct {
> + u64 desc;
> + u64 pa;
> + s8 level;
> + u8 APTable;
> + bool UXNTable;
> + bool PXNTable;
> + };
> + struct {
> + u8 fst;
> + bool ptw;
> + bool s2;
> + };
> + };
> + bool failed;
> +};
> +
> +static void fail_s1_walk(struct s1_walk_result *wr, u8 fst, bool ptw, bool s2)
> +{
> + wr->fst = fst;
> + wr->ptw = ptw;
> + wr->s2 = s2;
> + wr->failed = true;
> +}
> +
> +#define S1_MMU_DISABLED (-127)
> +
> +static int setup_s1_walk(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
> + struct s1_walk_result *wr, const u64 va, const int el)
> +{
> + u64 sctlr, tcr, tg, ps, ia_bits, ttbr;
> + unsigned int stride, x;
> + bool va55, tbi;
> +
> + wi->nvhe = el == 2 && !vcpu_el2_e2h_is_set(vcpu);
Where 'el' is computed in handle_at_slow() as:
/*
* We only get here from guest EL2, so the translation regime
* AT applies to is solely defined by {E2H,TGE}.
*/
el = (vcpu_el2_e2h_is_set(vcpu) &&
vcpu_el2_tge_is_set(vcpu)) ? 2 : 1;
I think 'nvhe' will always be false ('el' is 2 only when E2H is set).
I'm curious about what 'el' represents. The translation regime for the AT
instruction?
Thanks,
Alex
