[PATCH] RISC-V: KVM: Using user-mode pte within kvm_riscv_gstage_ioremap

[Nutty.Liu]

On 8/7/2025 3:07 PM, fangyu.yu at linux.alibaba.com wrote:
> From: Fangyu Yu <fangyu.yu at linux.alibaba.com>
>
> Currently we use kvm_riscv_gstage_ioremap to map IMSIC gpa to the spa of
> guest interrupt file within IMSIC.
>
> The PAGE_KERNEL_IO property does not include user mode settings, so when
> accessing the IMSIC address in the virtual machine,  a  guest page fault
> will occur, this is not expected.
>
> According to the RISC-V Privileged Architecture Spec, for G-stage address
> translation, all memory accesses are considered to be user-level accesses
> as though executed in Umode.
>
> Signed-off-by: Fangyu Yu <fangyu.yu at linux.alibaba.com>
> ---
>   arch/riscv/kvm/mmu.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
Reviewed-by: Nutty Liu <nutty.liu at hotmail.com>

Thanks,
Nutty
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index 1087ea74567b..800064e96ef6 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -351,6 +351,7 @@ int kvm_riscv_gstage_ioremap(struct kvm *kvm, gpa_t gpa,
>   	int ret = 0;
>   	unsigned long pfn;
>   	phys_addr_t addr, end;
> +	pgprot_t prot;
>   	struct kvm_mmu_memory_cache pcache = {
>   		.gfp_custom = (in_atomic) ? GFP_ATOMIC | __GFP_ACCOUNT : 0,
>   		.gfp_zero = __GFP_ZERO,
> @@ -359,8 +360,11 @@ int kvm_riscv_gstage_ioremap(struct kvm *kvm, gpa_t gpa,
>   	end = (gpa + size + PAGE_SIZE - 1) & PAGE_MASK;
>   	pfn = __phys_to_pfn(hpa);
>   
> +	prot = pgprot_noncached(PAGE_WRITE);
> +
>   	for (addr = gpa; addr < end; addr += PAGE_SIZE) {
> -		pte = pfn_pte(pfn, PAGE_KERNEL_IO);
> +		pte = pfn_pte(pfn, prot);
> +		pte = pte_mkdirty(pte);
>   
>   		if (!writable)
>   			pte = pte_wrprotect(pte);