linux-kernel - Re: [PATCH 2/4] MIPS: kvm: Use vm_get_page

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Date:   Sat, 14 Nov 2020 15:34:14 +0800
From:   Huacai Chen <chenhc@...ote.com>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        kvm <kvm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] MIPS: kvm: Use vm_get_page_prot to get protection bits

Hi, Thomas,

On Fri, Nov 13, 2020 at 7:13 PM Thomas Bogendoerfer
<tsbogend@...ha.franken.de> wrote:
>
> MIPS protection bits are setup during runtime so using defines like
> PAGE_SHARED ignores this runtime changes. Using vm_get_page_prot
> to get correct page protection fixes this.
Is there some visible bugs if without this fix?

Huacai
>
> Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
> ---
>  arch/mips/kvm/mmu.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/mips/kvm/mmu.c b/arch/mips/kvm/mmu.c
> index 28c366d307e7..3dabeda82458 100644
> --- a/arch/mips/kvm/mmu.c
> +++ b/arch/mips/kvm/mmu.c
> @@ -1074,6 +1074,7 @@ int kvm_mips_handle_commpage_tlb_fault(unsigned long badvaddr,
>  {
>         kvm_pfn_t pfn;
>         pte_t *ptep;
> +       pgprot_t prot;
>
>         ptep = kvm_trap_emul_pte_for_gva(vcpu, badvaddr);
>         if (!ptep) {
> @@ -1083,7 +1084,8 @@ int kvm_mips_handle_commpage_tlb_fault(unsigned long badvaddr,
>
>         pfn = PFN_DOWN(virt_to_phys(vcpu->arch.kseg0_commpage));
>         /* Also set valid and dirty, so refill handler doesn't have to */
> -       *ptep = pte_mkyoung(pte_mkdirty(pfn_pte(pfn, PAGE_SHARED)));
> +       prot = vm_get_page_prot(VM_READ|VM_WRITE|VM_SHARED);
> +       *ptep = pte_mkyoung(pte_mkdirty(pfn_pte(pfn, prot)));
>
>         /* Invalidate this entry in the TLB, guest kernel ASID only */
>         kvm_mips_host_tlb_inv(vcpu, badvaddr, false, true);
> --
> 2.16.4
>