On Mon, Oct 04, 2021 at 06:48:46PM +0100, Marc Zyngier wrote:
> Implement the previously defined ioremap/iounmap hooks for arm64,
> calling into KVM's MMIO guard if available.
>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> arch/arm64/mm/ioremap.c | 112 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 112 insertions(+)
>
> diff --git a/arch/arm64/mm/ioremap.c b/arch/arm64/mm/ioremap.c
> index b7c81dacabf0..5334cbdc9f64 100644
> --- a/arch/arm64/mm/ioremap.c
> +++ b/arch/arm64/mm/ioremap.c
> @@ -9,13 +9,125 @@
> * Copyright (C) 2012 ARM Ltd.
> */
>
> +#define pr_fmt(fmt) "ioremap: " fmt
> +
> #include <linux/export.h>
> #include <linux/mm.h>
> #include <linux/vmalloc.h>
> +#include <linux/slab.h>
> #include <linux/io.h>
> +#include <linux/arm-smccc.h>
>
> #include <asm/fixmap.h>
> #include <asm/tlbflush.h>
> +#include <asm/hypervisor.h>
> +
> +struct ioremap_guard_ref {
> + refcount_t count;
> +};
> +
> +static DEFINE_STATIC_KEY_FALSE(ioremap_guard_key);
> +static DEFINE_XARRAY(ioremap_guard_array);
> +static DEFINE_MUTEX(ioremap_guard_lock);
> +
> +void ioremap_phys_range_hook(phys_addr_t phys_addr, size_t size, pgprot_t prot)
> +{
> + if (!static_branch_unlikely(&ioremap_guard_key))
> + return;
> +
> + if (pfn_valid(__phys_to_pfn(phys_addr)))
> + return;
> +
> + mutex_lock(&ioremap_guard_lock);
> +
> + while (size) {
> + u64 pfn = phys_addr >> PAGE_SHIFT;
> + struct ioremap_guard_ref *ref;
> + struct arm_smccc_res res;
> +
> + ref = xa_load(&ioremap_guard_array, pfn);
> + if (ref) {
> + refcount_inc(&ref->count);
> + goto next;
> + }
> +
> + /*
> + * It is acceptable for the allocation to fail, specially
> + * if trying to ioremap something very early on, like with
> + * earlycon, which happens long before kmem_cache_init.
> + * This page will be permanently accessible, similar to a
> + * saturated refcount.
> + */
> + ref = kzalloc(sizeof(*ref), GFP_KERNEL);
> + if (ref) {
> + refcount_set(&ref->count, 1);
> + if (xa_err(xa_store(&ioremap_guard_array, pfn, ref,
> + GFP_KERNEL))) {
> + kfree(ref);
> + ref = NULL;
> + }
> + }
> +
> + arm_smccc_1_1_hvc(ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_MAP_FUNC_ID,
> + phys_addr, prot, &res);
OK, I see this follows the document and passes prot in x2, even though the
hypercall implementation doesn't look at it [yet].
> + if (res.a0 != SMCCC_RET_SUCCESS) {
> + pr_warn_ratelimited("Failed to register %llx\n",
> + phys_addr);
> + xa_erase(&ioremap_guard_array, pfn);
> + kfree(ref);
> + goto out;
> + }
> +
> + next:
> + size -= PAGE_SIZE;
> + phys_addr += PAGE_SIZE;
Looks like we're assuming the guard granule to be PAGE_SIZE here. Looking
ahead at the next patch, I see it must be PAGE_SIZE, because if the info
hypercall doesn't have a matching value, then mmio guarding doesn't
happen at all. Maybe it should be documented that for this feature the
host and guest must have matching page sizes.
> + }
> +out:
> + mutex_unlock(&ioremap_guard_lock);
> +}
> +
> +void iounmap_phys_range_hook(phys_addr_t phys_addr, size_t size)
> +{
> + if (!static_branch_unlikely(&ioremap_guard_key))
> + return;
> +
> + VM_BUG_ON(phys_addr & ~PAGE_MASK || size & ~PAGE_MASK);
> +
> + mutex_lock(&ioremap_guard_lock);
> +
> + while (size) {
> + u64 pfn = phys_addr >> PAGE_SHIFT;
> + struct ioremap_guard_ref *ref;
> + struct arm_smccc_res res;
> +
> + ref = xa_load(&ioremap_guard_array, pfn);
> + if (!ref) {
> + pr_warn_ratelimited("%llx not tracked, left mapped\n",
> + phys_addr);
> + goto next;
> + }
> +
> + if (!refcount_dec_and_test(&ref->count))
> + goto next;
> +
> + xa_erase(&ioremap_guard_array, pfn);
> + kfree(ref);
> +
> + arm_smccc_1_1_hvc(ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_UNMAP_FUNC_ID,
> + phys_addr, &res);
> + if (res.a0 != SMCCC_RET_SUCCESS) {
> + pr_warn_ratelimited("Failed to unregister %llx\n",
> + phys_addr);
> + goto out;
> + }
> +
> + next:
> + size -= PAGE_SIZE;
> + phys_addr += PAGE_SIZE;
> + }
> +out:
> + mutex_unlock(&ioremap_guard_lock);
> +}
>
> static void __iomem *__ioremap_caller(phys_addr_t phys_addr, size_t size,
> pgprot_t prot, void *caller)
> --
> 2.30.2
>
Thanks,
drew
