Re: [PATCH 06/10] KVM: arm64: Use guard(mutex) in mmu.c

Jonathan Cameron
2026-03-17T17:50:53Z

On Mon, 16 Mar 2026 17:35:27 +0000
Fuad Tabba <tabba@google.com> wrote:

> Migrate manual mutex_lock() and mutex_unlock() calls managing
> kvm_hyp_pgd_mutex and hyp_shared_pfns_lock to use the
> guard(mutex) macro.
>
> This eliminates manual unlock calls on return paths and simplifies
> error handling by replacing unlock goto labels with direct returns.
> Centralized cleanup goto paths are preserved with manual unlocks
> removed.
>
> Change-Id: Ib0f33a474eb84f19da4de0858c77751bbe55dfbb
> Signed-off-by: Fuad Tabba <tabba@google.com>

> @@ -652,22 +632,20 @@ int hyp_alloc_private_va_range(size_t size, unsigned long *haddr)
> unsigned long base;
> int ret = 0;
>
> - mutex_lock(&kvm_hyp_pgd_mutex);
> -
> - /*
> - * This assumes that we have enough space below the idmap
> - * page to allocate our VAs. If not, the check in
> - * __hyp_alloc_private_va_range() will kick. A potential
> - * alternative would be to detect that overflow and switch
> - * to an allocation above the idmap.
> - *
> - * The allocated size is always a multiple of PAGE_SIZE.
> - */
> - size = PAGE_ALIGN(size);
> - base = io_map_base - size;
> - ret = __hyp_alloc_private_va_range(base);
> -
> - mutex_unlock(&kvm_hyp_pgd_mutex);
> + scoped_guard(mutex, &kvm_hyp_pgd_mutex) {
> + /*
> + * This assumes that we have enough space below the idmap
> + * page to allocate our VAs. If not, the check in
> + * __hyp_alloc_private_va_range() will kick. A potential
> + * alternative would be to detect that overflow and switch
> + * to an allocation above the idmap.
> + *
> + * The allocated size is always a multiple of PAGE_SIZE.
> + */
> + size = PAGE_ALIGN(size);
> + base = io_map_base - size;
> + ret = __hyp_alloc_private_va_range(base);
Minor one and matter of taste, but I'd do
if (ret)
return ret;
}
*hwaddr = base;

return 0;

> + }
>
> if (!ret)
> *haddr = base;
> @@ -711,17 +689,16 @@ int create_hyp_stack(phys_addr_t phys_addr, unsigned long *haddr)
> size_t size;
> int ret;
>
> - mutex_lock(&kvm_hyp_pgd_mutex);
> - /*
> - * Efficient stack verification using the NVHE_STACK_SHIFT bit implies
> - * an alignment of our allocation on the order of the size.
> - */
> - size = NVHE_STACK_SIZE * 2;
> - base = ALIGN_DOWN(io_map_base - size, size);
> + scoped_guard(mutex, &kvm_hyp_pgd_mutex) {
> + /*
> + * Efficient stack verification using the NVHE_STACK_SHIFT bit implies
> + * an alignment of our allocation on the order of the size.
> + */
> + size = NVHE_STACK_SIZE * 2;
> + base = ALIGN_DOWN(io_map_base - size, size);
>
> - ret = __hyp_alloc_private_va_range(base);
> -
> - mutex_unlock(&kvm_hyp_pgd_mutex);
> + ret = __hyp_alloc_private_va_range(base);
> + }
>
> if (ret) {
> kvm_err("Cannot allocate hyp stack guard page\n");
Maybe move this under the guard just to keep the error check nearer the code
in question.

Thanks,

Jonathan

>